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The use of ionic liquids as carriers of magnetorheological fluids is described by Schubert and co-workers on p. 1740. Combining the properties of ionic liquids with magnetorheological technology may lead to new, “smart” fluids for application in medical therapies, engineering devices, or multiphase biological and chemical systems. In the presence of a magnetic field the fluids behave as solids owing to a stronger interaction between their suspended magnetic particles. In the absence of the magnetic field, they become liquids again in a fully reversible process.

The outstanding properties of ionic liquids are combined with magnetorheological technology to obtain new and “smart” fluids (see figure and cover) that can be applied in diverse areas of research and technology, such as medical therapies (drug delivery and cancer therapeutic methods), engineering devices (dampers and breaks), and accurate transportation and delivery of substances in multiphase biological and chemical systems.

Supramolecular copolymers have become of increasing interest in recent years for the search of new materials with tunable properties. In particular, metallo-supramolecular block copolymers—copolymers in which the blocks are linked together by a metal–ligand complex—have seen important progresses, allowing better control over the synthetic strategies for various architectures, and providing a better understanding of the parameters governing their self-assembly. We review here recent developments on the synthesis and self-assembly of such materials achieved in this field.

Schubert and co-workers have performed a detailed investigation on ink-jet printing of well-defined dots of luminescent CdTe nanocrystals (NCs) embedded in a poly(vinyl alcohol) matrix, as reported on p. 23, and subsequently made studies of their morphology and photoluminescence. The inside cover shows a photograph of an ink-jet-printed combinatorial library of differently sized CdTe NCs emitting at different wavelengths, and a 3D profilometer image of an array of printed dots.

Inkjet printing is used to produce well-defined patterns of dots (with diameters of ca. 120 μm) that are composed of luminescent CdTe nanocrystals (NCs) embedded within a poly(vinylalcohol) (PVA) matrix. Addition of ethylene glycol (1–2 vol %) to the aqueous solution of CdTe NCs suppresses the well-known ring-formation effect in inkjet printing leading to exceptionally uniform dots. Atomic force microscopy characterization reveals that in the CdTe NC films the particle–particle interaction could be prevented using inert PVA as a matrix. Combinatorial libraries of CdTe NC–PVA composites with variable NC sizes and polymer/NC ratios are prepared using inkjet printing. These libraries are subsequently characterized using a UV/fluorescence plate reader to determine their luminescent properties. Energy transfer from green-light-emitting to red-light-emitting CdTe NCs in the composite containing green- (2.6 nm diameter) and red-emitting (3.5 nm diameter) NCs are demonstrated.

Inkjet printing is used to produce well-defined patterns of dots (with diameters of ca. 120 μm) that are composed of luminescent CdTe nanocrystals (NCs) embedded within a poly(vinylalcohol) (PVA) matrix. Addition of ethylene glycol (1–2 vol %) to the aqueous solution of CdTe NCs suppresses the well-known ring-formation effect in inkjet printing leading to exceptionally uniform dots. Atomic force microscopy characterization reveals that in the CdTe NC films the particle–particle interaction could be prevented using inert PVA as a matrix. Combinatorial libraries of CdTe NC–PVA composites with variable NC sizes and polymer/NC ratios are prepared using inkjet printing. These libraries are subsequently characterized using a UV/fluorescence plate reader to determine their luminescent properties. Energy transfer from green-light-emitting to red-light-emitting CdTe NCs in the composite containing green- (2.6 nm diameter) and red-emitting (3.5 nm diameter) NCs are demonstrated.

A detailed survey on the processing of poly[2-methoxy-5-(2′-ethylhexyloxyl)–1,4-phenylenevinylene] (MEH–PPV) solutions via ink-jet printing and the subsequent characterization of the resulting films is reported. The printability of MEH–PPV dissolved in different solvents, and with varied concentrations, is studied. Limitations of the printability of highly concentrated polymer solutions are overcome by using ultrasonication. The pattern formation of the resulting lines is explained in relation to the contact angle formed by the MEH–PPV solution on the substrate and interchain interactions. A uniform thickness distribution of MEH–PPV films is obtained when toluene is used as the solvent. Further improvement on the surface quality of the lines is achieved by optimizing the printing parameters. The line stability as a function of the print-head velocity is also studied. Additionally, current–voltage (I–V) characteristics and the morphology of the MEH–PPV films, as determined by atomic force microscopy, are discussed.

The ability of star-shaped, block copolymer-based unimolecular micelles to encapsulate and transport guest molecules was studied. Analytical ultracentrifugation studies clearly showed that methyl-orange guest molecules could be encapsulated and transported, together with unimolecular micelles consisting of 5-arm, star-shaped block copolymers with a poly(ethylene glycol) core and a poly(ε-caprolactone) corona. Sedimentation-velocity and equilibrium measurements were performed to determine the sedimentation coefficients, molar masses, and diffusion coefficients of the loaded, unimolecular micelles. It was observed that the transport of guest molecules by unimolecular micelles was a function of the molecular weight of the star-shaped block copolymers and therefore also of their size.

Microwave-assisted polymerizations is a growing field of interest because the use of microwave irradiation instead of thermal heating was demonstrated to result in faster, cleaner, and higher yielding reactions. To overcome the one-at-a-time nature of preparing polymerizations in single microwave vials and the possible scale-up method for microwave-assisted polymerizations, the use of continuous-flow reactions under microwave irradiation seems to be ideal. In this contribution, we report for the first time the use of different continuous-flow microwave reactors for polymerizations, using the cationic ring-opening polymerizations of 2-ethyl-2-oxazoline as a model system. In addition, the observed broader molecular-weight distributions were correlated to residence time distributions of the continuous-flow reactors that were determined using methyl orange as the flow marker.

The use of microwave irradiation has become a common heat source in organic chemistry. Inspired by this enormous success, the use of microwave irradiation is also increasingly studied for polymerization reactions. The present review discusses developments in this rapidly growing field of research. The main areas in which the use of microwave irradiation has been explored in the recent years are step-growth polymerizations, ring-opening polymerizations as well as radical polymerizations. These different areas will be addressed in detail, whereby special attention will be given to observed improvements resulting from the use of microwave irradiation as well as the occurrence of non-thermal effects.

Water-soluble ionic liquids (IL) were used as reaction media to perform homogeneous polymerizations under microwave irradiation. The investigated reaction systems include the free radical polymerization of methyl methacrylate and the cationic ring opening polymerizations of 2-phenyl-2-oxazoline and 2-(m-difluorophenyl)-2-oxazoline. The incorporation of ILs into the polymerizations showed a more efficient heating profile of the reaction mixtures under microwave irradiation in comparison to the cases without ILs. Moreover, a convenient approach for the polymer isolation and recovery of the ILs for further polymerizations is demonstrated taking advantage of the water solubility of the investigated ILs. This synthetic approach is an alternative, efficient, and green method for the manufacture of hydrophobic polymers which may allow depletion of the emission of volatile organic compounds into the environment and for energy savings.

A novel tetradentate amine ligand namely N,N,N′,N″,N‴;,N‴;-hexaoligo(ethylene glycol) triethylenetetramine (HOEGTETA) was employed in the homogenous ATRP of MMA in anisole using CuBr and CuBr₂ as the catalyst and ethyl 2-bromoisobutyrate (EBiB) as an initiator. The effect of the polymerization temperature and the various ratios of Cu(I) to Cu(II) were investigated in detail. Moreover, we demonstrated the ATRP of MMA by using only Cu(II) in the absence of any free radical initiator, reducing agent, or air. The ATRP of MMA with the use of only Cu(II) and HOEGTETA or N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) resulted in well-defined PMMA.

1-Alkyl-3-methylimidazolium-based ionic liquids, having chloride as a counter ion, were studied for cellulose solubility; and the influence of different alkyl chain lengths was also investigated. The alkyl chain length was incrementally varied from ethyl to decyl to determine structure-dissolution properties; a distinct odd-even effect was observed for short chain lengths. In addition, the tritylation of cellulose was performed in 1-butyl-3-methylimidazolium chloride using pyridine as base. The influences of reaction time and the ratio of trityl chloride per cellulose monomer unit on the degree of substitution were investigated in detail by elemental analysis and ¹H NMR spectroscopy. A DS of around 1 was obtained after 3 h reaction time using a six fold excess of trityl chloride.

A library of hydroxy- and amino-functionalized Kröhnke-type terpyridines have been used to synthesize new terpyridine end-functionalized poly(ε-caprolactone)s and poly(L-lactide)s, via Sn(II)-catalyzed ring-opening polymerization. It has also been possible to prepare a set of metallo-supramolecular AA homopolymers by complexation with Fe(II) metal ions. All of these complexes have been fully characterized. Stable metallo-polymers with an intense blue color have been obtained from the quaternized macroligands. This color property might be of great interest for the design of functional supramolecular materials, with respect to color tuning and optical applications.

One of the most important characterization methods for macromolecules is SEC. The main difficulty for this type of measurements concerning metallo-supramolecular polymers based on terpyridines is related to the interaction between the charged supramolecular species and the SEC column material. In this paper, we report new studies on the characterization and the stability of supramolecular polymers based on terpyridine metal complexes utilizing SEC. The main aspects concerning the equilibrium between complexed and uncomplexed species are discussed in detail. The present study reveals a strong relationship between the binding strength of the metal ion used and the stability of the terpyridine metal complex during the SEC measurements, which is in agreement with previously published results regarding the stability of small terpyridine metal complexes in solution. These results can lead to improved analytic possibilities and to a better fundamental understanding of the mentioned metallo-supramolecular polymers. Furthermore, the prepared chain-extended supramolecular-polymer was analyzed by depth-sensing indentation proving an increase in elastic modulus in comparison with the starting material.

The microwave-assisted statistical copolymerization of 2-phenyl-2-oxazoline with 2-methyl-2-oxazoline or 2-ethyl-2-oxazoline is discussed in this contribution. Kinetic studies of these statistical copolymerizations as well as reactivity ratio determinations were performed to investigate the monomer distribution in these copoly(2-oxazoline)s, demonstrating the formation of quasi-diblock copolymers. In addition, the synthesis of copolymer series with monomer concentrations ranging from 0 to 100 mol % is described. These copolymer series were characterized with ¹H NMR spectroscopy, gas chromatography, and gel permeation chromatography. Moreover, the glass-transition temperatures and solubility of these copolymers were studied, and this revealing better mixing of poly(2-methyl-2-oxazoline) (pMeOx) with poly(2-phenyl-2-oxazoline) (pPhOx) than poly(2-ethyl-2-oxazoline) (pEtOx) with poly(2-phenyl-2-oxazoline) (pPhOx). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 416–422, 2007.

The synthesis of statistical copolymers consisting of 2-ethyl-2-oxazoline (EtOx) and 2-“soy alkyl”-2-oxazoline (SoyOx) via a microwave-assisted cationic ring-opening polymerization procedure is described. The majority of the resulting copolymers revealed polydispersity indices below 1.30. The reactivity ratios (r_EtOx 1.4 ± 0.3; r_SoyOx = 1.7 ± 0.3) revealed a clustered monomer distribution throughout the polymer chains. The thermal and surface properties of the pEtOx-stat-SoyOx copolymers were analyzed before and after UV-curing demonstrating the decreased chain mobility after cross-linking. In addition, the cross-linked materials showed shape-persistent swelling upon absorption of water from the air, whereby as little as 5 mol % SoyOx was found to provide efficient cross-linking. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5371,–5379, 2007

Conductive silver tracks on a polyimide substrate (see figure) are prepared by using microwave radiation to sinter silver nanoparticles printed on the substrate. This method shortens the necessary sintering time dramatically and is independent of the substrate used. Since the polymer substrate is virtually transparent to microwave radiation, a negligible amount of energy is absorbed by the substrate, whereas the conducting silver nanoparticles, with a high dielectric loss factor, strongly absorb the microwaves.

Polymer microstructures are prepared by inkjet etching. By varying the distance between the printed solvent droplets, rectangular and honeycomb hole arrays like those shown in the figure are formed. These holes can act as reservoirs for other inkjet-printed materials, such as quantum dots. The technique holds promise for rapid- prototyping applications and microarray fabrication.

Scanning force spectroscopy (SFS) is a powerful tool for investigating surface properties with high precision. Unlike most common spectroscopic techniques, information about local properties can also be obtained from surface areas with nanometer dimensions. This makes SFS a useful investigative tool for small lithographic structures. We apply the continuous recording of force curves to extract valuable information about the local oxidation of a monolayer of n-octadecyltrichlorosilane molecules self-assembled on silicon. The oxidation is carried out while simultaneously recording the force curves during the application of a bias voltage to the tip. The dynamics of the induced surface modifications and changes in the surface properties are followed by analyzing specific spots in the force curves.

Summary: The use of microwave heating in polymer science is a rapidly growing field of research leading to faster and cleaner polymerization procedures. However, the majority of the investigations are performed at small scales (≈1 mL), which is far away from potential commercial applications of microwave-assisted polymerizations. In addition, it has been shown in organic chemistry that microwave-assisted reaction protocols can be directly scaled without the need for process optimization. In this contribution, we have investigated the direct scaling of microwave-assisted polymerization procedures under pressure conditions using the cationic ring-opening polymerization of 2-ethyl-2-oxazoline as the model system. This polymerization was performed at scales ranging from 4.0 mmol (1 mL) to 1.0 mol (250 mL) in different microwave synthesizers covering both monomode and multimode devices.

Summary: The influence of surface morphologies on the properties of materials is of essential importance and is therefore a widely discussed topic. In the present contribution, the properties of a set of diblock copoly(2-oxazoline)s are analyzed in terms of their individual morphologies, which have been investigated with tapping-mode SFM. This collection of diblock copolymers consists of 12 diblock copolymers and four corresponding homopolymers, representing a complete 16-membered library of (co-) poly(2-oxazoline)s, composed of four differently substituted 2-oxazoline monomers. For the investigated set of compounds, a correlation between the morphologies of the spin-coated films and their surface energies could be determined.

Summary: Applications of analytical ultracentrifugation in the field of synthetic polymers have followed a clearly increasing trend in the past few years, concerning the variety of investigated samples, experimental approaches, and methods of data analysis. We report a characterization study of two metallo-supramolecular diblock copolymers with different block lengths and of a chain extended metallo-supramolecular polymer. The analysis of sedimentation velocity and sedimentation equilibrium profiles was discussed in detail and the results were compared to each other, to determine the molar mass distribution and the state of association in solution. A simple method for determining the average translational diffusion coefficients is proposed and discussed relative to other methods. The average values of the molar mass and sedimentation coefficient distributions, the average friction coefficients, and size information were obtained and discussed.

Summary: Novel block copolymers were synthesized in a controlled fashion by nitroxide-mediated radical polymerization starting from a terpyridine-modified alkoxyamine. An important feature for controlling the efficiency of the polymerization is the presence of excess nitroxide, responsible for the initial rate of deactivation, which eventually leads to a decrease of the polydispersity indices of the desired block copolymer. The materials obtained were characterized by means of ¹H NMR, UV-vis spectroscopy, and GPC. The complexation of the terpyridine ligands resulted in the formation of A-B-[Ru]-C, A-B-[Ru]-B-A, and A-B-[Fe]-B-A metallo-supramolecular block copolymers.

Automated parallel synthesizers provide fast and comparable screening of different polymerization parameters under similar conditions. In addition, these robotic systems eliminate handling errors, which may affect the results of a kinetic experiment more than the effect of an important parameter. The polymerization temperature and N,N-tert-butyl-N-[1′-diethylphosphono-2,2′-dimethylpropyl]nitroxide concentration were optimized for the homopolymerization of both styrene and tert-butyl acrylate to improve the control over the polymerization while reasonable polymerization rates were retained. Subsequently, polystyrene and poly(tert-butyl acrylate) macro initiators were synthesized according to the knowledge obtained from the screening results. These macroinitiators were used for the preparation of block copolymers consisting of styrene and tert-butyl acrylate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6202–6213, 2006

Aqueous solutions of ionic liquids have been used as novel and environmentally friendly reaction media to synthesize and “control” the size of different cross-linked polymer beads by suspension polymerization reactions. It was found that the investigated ionic liquids can act as novel stabilizing agents of the suspensions as a result of their surface-active properties. The results have demonstrated that the average size of polymer beads can be varied from the macro- to the nanoscale and their surface area can also be “adjusted” by this synthetic approach. Furthermore, the use of a combination of ionic liquids and water for the synthesis of polymers, the simple isolation of the products formed in this polymerization procedure, as well as the recycling of the continuous medium for further reactions open up possibilities for the development of “new and green” polymerization processes.

Nanoporous thin polymer films have been produced by a simple two-step approach using metallo-supramolecular block copolymers as the starting materials. The first step is the self-assembly of the copolymer, yielding cylindrical microdomains oriented normal to the substrate. The second step involves the opening of the metal–ligand complex located at the junction of the two blocks by redox chemistry to release the minor block and create the pores (see Figure).

The advantage of using phosphorescent transition metal–ligand complexes in optoelectronic applications such as organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LECs) are described and evaluated. Additionally, different device constructions utilizing phosphorescent transition-metal complexes like iridium(III) mixed-ligand complexes and ruthenium(II) systems are reviewed and specified. Diverse host materials in which the phosphorescent emitters can be placed are discussed, such as small organic molecules and a few polymeric systems, and alternative processing technologies are briefly compared. Recent developments in the synthesis of iridium(III) triplet emitters are discussed. Different device architectures require different kinds of metal–ligand complexes. The different synthetic routes leading to charged and non-charged complexes are briefly discussed.

Schubert and co-workers have performed a detailed atomic force microscopy study to establish and characterize the oxidation conditions of self-assembled monolayers of octadecyl trichlorosilane on silicon substrates. The cover image illustrates different examples of surfaces that were structured with different patterning conditions, as reported on p. 938. The graph in the background depicts three observed oxidation regimes depending on applied voltage and oxidation time.

In current scanning-probe nanolithography research, substrates consisting of octadecyl trichlorosilane monolayers on silicon are often used. On one hand, the presence of an organic monolayer can be used as a passive resist, influencing the formation of silicon dioxide on the substrate, whereas in other cases the monolayer itself is patterned, creating local chemical functionality. In this study we investigate the time scales involved in either process. By looking at friction and height images of lines oxidized at different bias voltages and different pulse durations, we have determined the parameter space in which the formation of silicon dioxide is dominant as well as the region in which the oxidation of the monolayer itself is dominant.

In current scanning-probe nanolithography research, substrates consisting of octadecyl trichlorosilane monolayers on silicon are often used. On one hand, the presence of an organic monolayer can be used as a passive resist, influencing the formation of silicon dioxide on the substrate, whereas in other cases the monolayer itself is patterned, creating local chemical functionality. In this study we investigate the time scales involved in either process. By looking at friction and height images of lines oxidized at different bias voltages and different pulse durations, we have determined the parameter space in which the formation of silicon dioxide is dominant as well as the region in which the oxidation of the monolayer itself is dominant.

Summary: Investigations regarding the cationic ring-opening polymerization of 2-phenyl-2-oxazoline under microwave irradiation and conventional heating are reported. This study was inspired by contradictory reports of the (non-)existence of non-thermal microwave effects that might accelerate the cationic ring-opening of 2-oxazolines. The polymerization of 2-phenyl-2-oxazoline was investigated under pressure in acetonitrile and under reflux (or at the boiling point of butyronitrile in a closed vessel) in butyronitrile utilizing a single-mode microwave reactor and automated synthesis robots with conventional heating.

Summary: The phase behavior of metallo-supramolecular block copolymers with bulky counter ions is theoretically studied within the framework of a mean-field dynamic density functional theory and compared with recent experiments on a polystyrene–poly(ethylene oxide) metallo-supramolecular diblock copolymer, PS₂₀-[Ru]-PEO₇₀, with tetraphenylborate counter ions. The copolymer is modeled as a triblock polyelectrolyte, in which the metal complex is treated as the polyelectrolyte block. The topology and kinetics of the formation of the observed three-domain lamellar morphology in which the polyelectrolyte blocks and bulky counter ions are located together to form electroneutral complexes, are in good agreement with experimental results. In addition, the model predicts the existence of core–shell morphologies. The agreement with and variations from the experimental phase diagram are discussed in detail.

Summary: A series of poly(ethylene glycol)-block-poly(ε-caprolactone) diblock copolymers was synthesized and fully characterized. In particular, MALDI-TOF MS results revealed interesting new insights into their molecular architecture. Small and defined micelles could be prepared from these block copolymers. Utilizing a high-throughput screening approach, it was observed that these micelles are able to encapsulate/solubilize different guest molecules (e.g. drugs) depending on the solubility of the guest in water. Furthermore, it could be proven that a guest is located within a micelle and that these micelles can be utilized as transport vehicles for the encapsulated guest molecules.

Summary: The influence of architecture on ink-jet printability of polymer solutions is investigated by comparing linear and 6-arm star PMMA. At comparable concentration and molecular weight, filament formation is much more pronounced for linear PMMA than for star PMMA. Visual examination of filament stretching allows estimation of the involved elongation rates, which are at high voltages sufficiently large for coil-stretch transition of the chains, suggesting its role in filament formation.

Summary: Defined films of luminescent ruthenium(II) polypyridyl-poly(methyl methacrylate) (PMMA) and iridium(III) polypyridyl-polystyrene (PS) copolymers could be prepared by ink-jet printing. The copolymers were deposited on photoresist-patterned glass substrates. Films as thin as 120 nm could be printed with a roughness of 1 to 2%. In addition, the film thickness could be varied in a controlled way through the number of droplets deposited per unit area. The topography of the ink-jet printed films was analyzed utilizing an optical profilometer. The absorbance and emission spectra were measured using fast parallel UV-vis and fluorescence plate reader.

Summary: We illustrate the ink-jet printing of a thin-film library of donor/acceptor systems useful in bulk heterojunction solar cells and their characterization utilizing a UV-vis/fluorescence plate reader and an optical profilometer. In addition, the morphology of the films has been examined by atomic force microscopy (AFM). The ink-jet processing technology allows printing of arrays of different donor/acceptor compositions on one substrate as well as the subsequent fast optical screening of the electron transfer processes. The investigated films consist of blends of a poly(methyl methacrylate) polypyridyl ruthenium(II) copolymer (RuPMMA) as electron donor material (p-type) and C₆₀ fullerene (PC₆₀BM) as well as heptyl viologen (C₇-V) derivatives as electron acceptor materials (n-type).

Summary: On the basis of terpyridine functionalized poly(ethylene oxide) (PEO) and poly(styrene) (PS), a series of light-emitting iridium(III) compounds was effectively synthesized. The respective iridium(III) target compounds were prepared by grafting chloro-bridged precursor complexes [Ir(ppy)₂-μ-Cl]₂ (ppy = phenylpyridine) and [Ir(ppy-CHO)₂-μ-Cl]₂ (ppy-CHO = 4-(2-pyridyl)benzaldehyde) onto terpyridine functionalized PEO and PS tails. 1D and 2D NMR characterization was performed revealing the expected resonances. Gel permeation chromatography (GPC) proved the stability and purity of the targeted materials. Preliminary investigations of the light-emitting properties were carried out by standard methods such as UV-vis and steady-state luminescence spectroscopy. The morphology and the quality of films of these iridium(III) compounds were furthermore investigated using AFM. Improved stability on the electrode surface was illustrated using cyclic voltammetry. One of the polymer materials was compared to the neat complex, which showed quick degradation.

Poly(acrylate)s as well as poly(methacrylate)s were successfully synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerizations using 2-cyano-2-butyl dithiobenzoate (CBDB) as RAFT-agent. Four different ratios of RAFT to initiator were screened for four acrylates and four methacrylates using automated parallel synthesizer robots. The reactions were monitored by gel permeation chromatography (GPC) and gas chromatography (GC). The knowledge obtained during this screening was used for the designed synthesis of block and random copolymers containing a water- and a non water-soluble monomer. The results obtained from GPC analysis together with ¹H NMR spectroscopy demonstrate the possibility to design and prepare well-defined block and random copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3831–3839, 2005

Anionic polymerization techniques have been implemented successfully in a commercial automated synthesizer. The main problems for a successful adaptation of the experimental technique in the automated synthesizer are addressed, as well as some simple potential applications, such as the anionic polymerization of styrene, isoprene, and methyl methacrylate. The obtained results were reproducible and in concordance with literature knowledge. The apparent rate constant of the anionic polymerization of styrene in cyclohexane initiated by sec-butyllithium could be determined at two different concentrations of the monomer and initiator in a temperature range of 10–60 °C. All the synthesis and characterization experiments of the polymers were performed within a short time period. Moreover, the syntheses of poly(styrene-b-isoprene) and poly(styrene-b-methyl methacrylate) block copolymers were also successfully carried out within the automated synthesizer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4151–4160, 2005

A set of novel greenish-yellow-, yellow-, and orange-light-emitting polymeric iridium(III) complexes were synthesized with the bridge-splitting method. The respective dimeric precursor complexes, [Ir(ppy)₂-μ-Cl]₂ (ppy = 2-phenylpyridine) and [Ir(ppyCHO)₂-μ-Cl]₂ [ppyCHO = 4-(2-pyridyl)benzaldehyde], were coordinated to 2,2′-bipyridine carrying poly(ε-caprolactone) tails. The resulting emissive polymers were characterized with one-dimensional (¹H) and two-dimensional (¹H¹H correlation spectroscopy) nuclear magnetic resonance and infrared spectroscopy, gel permeation chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and the successful coordination of the iridium(III) centers to the 2,2′-bipyridine macroligand was revealed. The thermal behavior was studied with differential scanning calorimetry and correlated with atomic force microscopy. Furthermore, the quantitative coordination was verified by both the photophysical and electrochemical properties of the mononuclear iridium(III) compounds. The photoluminescence spectra showed strong emissions at 535 and 570 nm. The color shifts depended on the substituents of the cyclometallating ligands. Cyclic voltammetry gave oxidation potentials of 1.23 V and 1.46 V. Upon the excitation of the films at 365 nm, yellow light was observed, and this could allow potential applications in light-emitting devices. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2765–2776, 2005

The monomer concentration for the cationic ring-opening polymerization of 2-ethyl-2-oxazoline in N,N-dimethylacetamide was optimized utilizing high-throughput experimentation methods. Detailed ¹H-NMR spectroscopic investigations were performed to understand the mechanistic aspects of the observed concentration effects. Finally, the improved polymerization concentration was applied for the synthesis of higher molecular weight (> 10,000 Da) poly(2-ethyl-2-oxazoline)s. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1487–1497, 2005

New inorganic–organic hybrid structures based on metal complexes have become of increasing interest over the last few decades in the search for new materials. Many different polypyridyl metal complexes have been investigated. Recently, a strong increase in interest regarding 2,2′:6′,2″-terpyridine has been observed. In particular, octahedral bis-2,2′:6′,2″-terpyridine metal complexes offer the advantages of increased symmetry and, in the case of ruthenium(III)/ruthenium(II) complexation, an entrance to a directed complexation technique. Apart from the combination with polymeric systems, ordered inorganic–organic structures on surfaces are becoming better understood concurrently with the development of sophisticated nanotechnology characterization techniques. There are many ongoing efforts that include terpyridine complex structures, especially concerning photophysical processes such as solar light to energy conversion. This review deals with the incorporation of terpyridine complexes into polymeric structures such as poly(ethylene glycol), poly(styrene), dendrimers, biomacromolecules, micelles, and resins, as well as the combination of terpyridine complexes with surfaces for electrocatalytic, photophysical, and self-assembly purposes.

Summary: The temperature dependency of the polymerization of 2-phenyl-2-oxazoline was investigated utilizing a commercially available automated synthesizer equipped with individually heatable reactors. Kinetic investigations resulted in an optimal polymerization temperature and activation energy determination for the polymerizations initiated with methyl tosylate. Moreover, the in situ generation of benzyl iodide (more reactive initiator) from benzyl chloride and sodium iodide is described, whereby solid sodium iodide was automatically dosed into the reactors.

Summary: Automated parallel synthesis and high-throughput screening has been proven to drastically speed up polymer and materials research. Here we present an automated parallel approach for investigation of the influences of different counter ions (chloride, bromide, acetate and sulfate) on the iron(II) mediated metallo-supramolecular polymerization of bis(2,2′:6′,2″-terpyrid-4′-yl)-poly(ethylene oxide)₁₇₉. The synthesized polymers were characterized by ¹H NMR, UV-vis and IR. The degree of polymerization has been estimated on the basis of concentration dependent viscosity measurements. The conversion as well as the degree of polymerization followed the order: bromide, chloride > sulfate ≫ acetate.

Summary: Emerging from the field of biochemistry and pharmaceutical research, combinatorial and high-throughput synthesis and screening methodologies are rapidly being adopted in polymer and materials research. Alternative solutions to cost intensive custom-made synthetic robot systems have become commercially available and further accelerate this field of research not just in industry, but also in an academic environment. High-throughput analysis, materials characterization, and testing (surface energy, hardness, wettability, crystallinity etc.) are key techniques and require suitable instrumentation. Here we present a short overview of recent developments of robotic synthesizers and analytical equipment extending the review from January 2003.

Summary: A study is presented on ink-jet printing polymers, aiming at library generation for combinatorial material science applications, using (optimized) micropipettes. Solvents were successfully ink-jet printed, up to 160 mPa s viscosity. Printability of polymer solutions decreases strongly with and polymer concentration, due to elastic stresses originating from elongational flow in the pipette nozzle. The feasibility of ink-jet printing to generate arrays of polymer dots and films was demonstrated.

Summary: For speeding-up preparation as well as investigating new polymeric materials, combinatorial techniques, parallel experimentation, and high-throughput screening methods represent a very promising approach in polymer chemistry: a large variety of parameters can be screened simultaneously resulting in new structure–property relationships. As previously described, polymer chemistry seems to be perfectly suited for combinatorial approaches since it is relatively easy to vary many parameters during the synthesis, processing, blending, or compounding. Moreover, the development and application of high-throughput screening techniques for polymer properties can accelerate the development of new materials and can result in new structure–property relationships. Therefore, these screening tools, together with parallel preparation techniques, will significantly decrease the time to market of new products. Here we provide an update of our recent overview covering new developments in the field of combinatorial and parallel polymer synthesis and high-throughput screening.

Summary: The success of automated and parallel drug-discovery workflows in pharmaceutical research has sparked similar developments in materials science. This contribution provides an overview of published high-throughput experimentation work in the area of polymeric coatings and thin films. Methodological aspects, experimental examples, and remaining challenges are discussed.

Summary: Combinatorial and high-throughput experimentation has, over the past few years, started to play an increasingly important role in the area of materials and polymer science. However, many of the informatics tools currently available to support combinatorial experimentation were developed with the needs of medicinal and biological chemistry in mind. Recently, companies specialising in cheminformatics software have begun to address the need for dedicated materials informatics tools and, although still in its infancy, the development of such tools is rapidly gathering pace. This short review provides a summary of the current state-of-the-art.

Summary: Gel permeation chromatography (GPC) and gas chromatography (GC) were successfully introduced into a high-throughput workflow. The feasibility and limitations of online GPC with a high-speed column was evaluated by measuring polystyrene standards and comparison of the results with regular offline GPC measurements. The reliability of the online GC characterization was investigated by monitoring the cationic ring-opening-polymerization of 2-ethyl-2-oxazoline, whose polymerization kinetics were determined by both online and offline GC.

Summary: The first monomode microwave-assisted atom transfer radical polymerization (ATRP) is reported. The ATRP of methyl methacrylate was successfully performed with microwave heating, which was well controlled and provided almost the same results as experiments with conventional heating, demonstrating the absence of any “microwave effect” in ATRP (in contrast to several literature reports). Furthermore, we found that the main advantage of the microwave-assisted reactions over conventional reactions, i.e., a significant increase of reaction rates, only had its limited application in ATRP, even in very slow ATRP systems with high targeted molecular weights.

Summary: The coordinative polymerization/cyclization of a flexible monodisperse di-terpyridine ligand with iron(II) chloride is reported. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) investigations showed the preferred formation of a [2 + 2] macrocycle, but also larger aggregates (cycles or linear oligomers) with up to 10 monomer units were found. Because of its C₁₆-spacer, the solubility is sufficient for performing viscosity experiments in CHCl₃/MeOH solution. A viscosity titration revealed a maximum in viscosity at the 1-to-1 ratio of iron(II) ions to di-terpyridine-ligands, which indicates the formation of extended oligomers, polymers, catenanes and/or cycles at that ratio.

Summary: An amino-functionalized bipyridine ligand was prepared in order to serve as a bridging unit to an activated low-molecular-weight monomethyl ether of poly(ethylene glycol) (PEG). Coordination of a ruthenium(II) phenantroline precursor onto the formed PEG-containing bipyridine ligand yielded a metal-containing polymer which shows interesting properties for solar cell applications.

Summary: A monoterpyridine-poly(ethylene glycol) (mono-tpy-PEG) and a novel monoterpyridine-PEG-functionalized iridium(III) complex were successfully synthesized and fully characterized by means of NMR, IR, and UV-vis spectroscopy, as well as gel permeation chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The functionalized monoterpyridine iridium(III) complex was synthesized by a bridge-splitting reaction of a dimeric iridium(III) precursor complex using a chelating terpyridine ligand with a poly(ethylene glycol) tail. With this approach, a new class of light-emitting polymeric materials revealing interesting optical properties was made avaialable.

Summary: Monomodal microwaves have overcome the safety uncertainties associated with the precedent domestic microwave ovens. After fast acceptance in inorganic and organic syntheses, polymer chemists have also recently discovered this new kind of microwave reactor. An almost exponential increase of the number of publications in this field reflects the steadily growing interest in the use of microwave irradiation for polymerizations. This review introduces the microwave systems and their applications in polymer syntheses, covering step-growth and ring-opening, as well as radical polymerization processes, in order to summarize the hitherto realized polymerizations. Special attention is paid to the differences between microwave-assisted and conventional heating as well as the “microwave effects”.

Summary: The ring-opening cationic polymerization of 2-ethyl-2-oxazoline was performed in a single-mode microwave reactor as the first example of a microwave-assisted living polymerization. The observed increase in reaction rates by a factor of 350 (6 h  1 min) in the range from 80 to 190 °C could be attributed solely to a temperature effect as was clearly shown by control experiments and the determined activation energy. Because of the homogenous microwave irradiation, the polymerization could be performed in bulk or with drastically reduced solvent ratios (green chemistry).

Summary: The feasibility of automated, high-throughput contact-angle measurements is demonstrated using a modified commercial contact-angle measuring apparatus. Droplets are automatically dispensed, analyzed and aspirated. The system automatically measures more than 100 contact angles per hour using two test liquids, and calculates surface energies using the equation of state method. A library of poly(2-oxazoline) homo- and block copolymers was investigated. Polymers with a 2-nonyl-2-oxazoline block were found to have considerably lower surface energies.

The latest synthetic strategies to prepare 2,2′-bipyridine and its mono-substituted, symmetrical and unsymmetrical 3,3′-, 4,4′-, 5,5′-, and 6,6′-disubstituted derivatives are critically discussed and evaluated. Different coupling procedures to achieve new symmetrical and unsymmetrical functionalized 2,2′-bipyridines, such as Stille-type, Negishi-type, and Suzuki-type cross-coupling reactions are discussed in detail. Moreover, condensation procedures that allow further variations are presented. The application of functional group transformations for access to additional groups is examined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

A hydroxy-functionalized bipyridine ligand was polymerized with ε-caprolactone utilizing the controlled ring-opening polymerization of ε-caprolactone in the presence of stannous octoate. The resulting poly(ε-caprolactone)-containing bipyridine was characterized by ¹H NMR and IR spectroscopy, and gel permeation chromatography, as well as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, revealing the successful incorporation of the bipyridine ligand into the polymer chain. Coordination to iridium(III) and ruthenium(II) precursor complexes yielded two macroligand complexes, which were characterized by NMR, gel permeation chromatography, matrix-assisted laser desorption/ionization time-of-flight MS, cyclic voltammetry, and differential scanning calorimetry. In addition, both photophysical and electrochemical properties of the metal-containing polymers proved the formation of a trisruthenium(II) and a trisiridium(III) polypyridyl species, respectively. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4153–4160, 2004

A supramolecular AB diblock copolymer has been prepared by the sequential self-assembly of terpyridine end-functionalized polymer blocks by using Ru^III/Ru^II chemistry. By this synthetic strategy a hydrophobic poly(ferrocenylsilane) (PFS) was attached to a hydrophilic poly(ethylene oxide) (PEO) block to give an amphiphilic metallo-supramolecular diblock copolymer (PEO/PFS block ratio 6:1). This compound was used to form micelles in water that were characterized by a combination of dynamic and static light scattering, transmission electron microscopy, and atomic force microscopy. These complementary techniques showed that the copolymers investigated form rod-like micelles in water; the micelles have a constant diameter but are rather polydisperse in length, and light scattering measurements indicate that they are flexible. Crystallization of the PFS in these micelles was observed by differential scanning calorimetry, and is thought to be the key behind the formation of rod-like structures. The cylindrical micelles can be cleaved into smaller rods whenever the temperature of the solution is increased or they are exposed to ultrasound.

Da photolithographisch nicht beliebig kleine Bauelemente hergestellt werden können, werden andere Strukturierungstechniken intensiv untersucht. Insbesondere Rastersondenlithographie-Techniken gelten als vielversprechend für die Erzeugung solcher Strukturen, und da ihre Anwendung relativ einfach ist, sind diese Methoden inzwischen weit verbreitet. Beispiele sind die Dip-Pen-Lithographie und die kraftinduzierte lokale Strukturierung ebenso wie die lokale Oxidation mit Sonden. Diese Techniken sind besonders interessant, da so Nanostrukturen erhalten werden, die chemisch und physikalisch modifiziert und funktionalisiert werden können. Somit ist nicht nur die Produktion von elektronischen Bauelementen möglich, sondern auch die Erzeugung von Strukturen für die molekulare Erkennung oder die Sensorik. Wir zeigen hier die Fortschritte bei der Entwicklung von automatisierten Multispitzen-Rastersondensystemen und ihre Anwendung bei der lokalen Oxidation. Außerdem erläutern wir den Stand der Technik und die Perspektiven von Nanobauelementen.

The size regime for devices produced by photolithographic techniques is limited. Therefore, other patterning techniques have been intensively studied to create smaller structures. Scanning-probe-based patterning techniques, such as dip-pen lithography, local force-induced patterning, and local-probe oxidation-based techniques are highly promising because of their relative ease and widespread availability. The latter of these is especially interesting because of the possibility of producing nanopatterns for a broad range of chemical and physical modification and functionalization processes; both the production of nanometer-sized electronic devices and the formation of devices involving (bio)molecular recognition and sensor applications is possible. This Review highlights the development of various scanning probe systems and the possibilities of local oxidation methods, as well as giving an overview of state-of-the-art nanometer-sized devices, and a view of future development.

The controlled atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) catalyzed by iron halide/N-(n-hexyl)-2-pyridylmethanimine (NHPMI) is described. The ethyl 2-bromoisobutyrate (EBIB)-initiated ATRP with [MMA]₀/[EBIB]₀/[iron halide]₀/[NHPMI]₀ = 150/1/1/2 was better controlled in 2-butanone than in p-xylene at 90 °C. Initially added iron(III) halide improved the controllability of the reactions in terms of molecular weight control. The p-toluenesulfonyl chloride (TsC1)-initiated ATRP were uncontrolled with [MMA]₀/[TsC1]₀/[iron halide]₀/[NHPMI]₀ = 150/1/1/2 in 2-butanone at 90 °C. In contrast to the EBIB-initiated system, the initially added iron(III) halide greatly decreased the controllability of the TsC1-initiated ATRP. The ration of iron halide to NHPMI significantly influenced the controllability of both EBIB and TsC1-initiated ATRP systems. The ATRP with [MMA]₀/[initiator]₀/[iron halide]₀/[NHPMI]₀ = 150/1//1/2 provided polymers with PDIs ≥ 1.57, whereas those with [iron halide]₀/[NHPMI]₀ = 1 resulted in polymers with PDIs as low as 1.35. Moreover, polymers with PDIs of approximately 1.25 were obtained after their precipitation from acidified methanol. The high functionality of the halide end group in the obtained polymer was confirmed by both ¹H NMR and a chain-extenstion reaction. Cyclic voltammetry was utilized to explain the differing catalytic behaviors of the in situ-formed complexes by iron halide and NHPMI with different molar ratios. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4882–4894, 2004

High-throughput experimentation (HTE) was successfully applied in atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) for the rapid screening and optimization of different reaction conditions. A library of 108 different reactions was designed for this purpose, which used four different initiators [ethyl 2-bromoisobutyrate, methyl 2-bromopropionate, (1-bromoethyl)benzene, and p-toluenesulfonyl chloride], five metal salts (CuBr, CuCl, CuSCN, FeBr₂, and FeCl₂), and nine ligands (2,2′-bipyridine and its derivatives). The optimal reaction conditions for Cu(I) halide, CuSCN, and Fe(II) halide-mediated ATRP systems with 2,2′-bipyridine and its 4,4′-dialkyl-substituted derivatives as ligands were determined. Cu(I)-mediated systems were better controlled than Fe(II)-mediated ones under the examined conditions. A bipyridine-type ligand with a critical length of the substituted alkyl group (i.e., 4,4′-dihexyl 2,2′-bipyridine) exhibited the best performance in Cu(I)-mediated systems, and p-toluenesulfonyl chloride and ethyl 2-bromoisobutyrate could effectively initiate Cu(I)-mediated ATRP of MMA, resulting in polymers with low polydispersities in most cases. Besides, Cu(I) halide-mediated ATRP with 4,5′-dimethyl 2,2′-bipyridine as the ligand and p-toluenesulfonyl chloride as the initiator proved to be better controlled than those with 4,4′-dimethyl 2,2′-bipyridine as the ligand, and polymers with much lower polydispersities were obtained in the former cases. This successful HTE example opens up a way to significantly accelerate the development of new catalytic systems for ATRP and to improve the understanding of structure–property relationships of the reaction systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1876–1885, 2004

The systematical kinetic investigations of four 2-substituted-2-oxazoline monomers with four initiators at two temperatures and four monomer/initiator ratios are described. To cover this broad range of variables (128 different combinations), an automated synthesizer was used to accelerate the investigations and to provide highly comparable results. With both gas chromatography and gel permeation chromatography, the livingness and the polymerization rates were determined for the different polymerizations. The resulting insights in the kinetics were used for the directed synthesis of truly random copolymers and copolymers with composition drift. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1830–1840, 2004

Methyl methacrylate-containing bipyridine monomers were synthesized with a hydoxy-functionalized bipyridine. The 4′-methyl group of the 2,2′-bipyridine was used to introduce hydoxy-functionalized alkyl spacers of two different lengths. Two, different synthetic routes were applied for the preparation of the hydoxy-functionalized bipyridine via a bromo-(C₇ spacer) or a silylated-(C₃ spacer) intermediate. A copolymer of poly(methyl methacrylate) with bipyridine units in the side chains was prepared by free-radical copolymerization and characterized with ¹H NMR, ultraviolet–visible, and IR spectroscopy as well as gel permeation chromatography. The bipyridine units of the copolymer were reacted with ruthenium bipyridine precursors. The resulting graft copolymers displayed promising photophysical and electrochemical properties, opening interesting perspectives for applications in the field of solar-cell devices. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 374–385, 2004

Electrokinetic chromatography was employed to separate the enantiomers of two novel functionalized ruthenium(II) complexes with different polypyridyl coordination spheres. The use of anionic carboxymethyl-β-cyclodextrin as chiral mobile phase additive resulted in maximum efficiency and resolution for the enantiomer separation of both transition metal complexes. The syntheses of the [4-(3-hydroxypropyl)-4′-methyl-2,2′-bipyridine]-bis(2,2′-bipyridine)rethenium(II)-bis(tetrafluoroborate) and [4-(3-hydroxypropyl)-4′-methyl-2,2′-bipyridine]-bis(4,4′-dimethyl-2,2′-bypyridine)ruthenium(II)-bis(tetrafluoroborate) complexes and their complete characterization by means of two-dimensional ¹H and ¹³C{¹H} NMR techniques (¹H–¹H COSY and ¹H–¹³C HMQC) as well as elemental analyses and MALDI-TOFMS are described in detail. The functionalized complexes can be used as building blocks for further reactions with polymers, biopolymers, surfaces and nanoparticles. Chirality 16:363–368, 2004. © Wiley-Liss, Inc.

Poly(methyl methacrylate)s were successfully synthesized in a controlled fashion via reversible addition-fragmentation chain transfer polymerizations utilizing an automated synthesizer. Sixteen polymers were synthesized in a parallel way utilizing the Chemspeed Accelerator™ SLT100 to investigate the reproducibility and the control over the polymerizations. The obtained polymers were characterized by gel permeation chromatography (GPC) and automated MALDI TOFMS measurements, thereby proving the reproducibility and controllability of the investigated automated setup. Furthermore, temperature optimization reactions were performed utilizing an individually heatable reactor block. Moreover, to demonstrate the presence of active polymer chains in the reaction mixture, chain extension polymerizations were performed on the automated synthesizer. The results obtained from these chain extension experiments demonstrate the possibility to design well-defined A-b-B block copolymers with different monomers as building units. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5775–5783, 2004

Terpolymers bearing terpyridine as well as (meth)acrylates as free radical curable groups (UV-curing) or hydroxyl groups (thermal curing with bis-isocyanates) were synthesized and characterized using ¹H NMR, IR and UV-vis spectroscopy as well as GPC. Subsequently, the ability of covalent crosslinking via the UV-initiated polymerization of the acrylate groups was investigated. Moreover, the thermal covalent crosslinking via the reaction of hydroxyl functionalized terpolymer and bis-isocyanate compounds could be successfully achieved. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4028–4035, 2004

Nitroxide-mediated, controlled living radical polymerization was employed to introduce terpyridine ligands at one or two chain ends of polystyrene. For this purpose, a unimolecular initiator bearing both a terpyridine ligand as well as a mediating nitroxide was synthesized and used for the controlled polymerization of styrene. Moreover, a maleimide-functionalized terpyridine was prepared in order to synthesize telechelic polymers, utilizing nitroxide substitution reactions. Kinetic studies of the polymerization of styrene were carried out. In all polymerizations, special attention was focused on the retention of end-group functionality, in light of the effects of autoinitiation and autopolymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4016–4027, 2004

Single-molecule force spectroscopy has been used for the investigation of the rupture behavior of individual metallo-supramolecular systems. For this purpose, a specifically designed unsymmetrical α,ω-functionalized poly(ethylene oxide) has been employed for mono-termination with a terpyridine ligand and subsequently for the attachment onto atomic force microscopy (AFM) tips and microscope slide substrates. Metallo-supramolecular complexes were formed by the use of ruthenium(III)–ruthenium(II) chemistry. Vertical stretching with the AFM cantilever ruptured the coordinative bonds. The rupture force of individual bisterpyridine ruthenium(II) complexes was determined to be 95 pN at a force loading rate of 1 nN s^–1. Simultaneous rupturing of multiple parallel metallo-supramolecular bonds was also observed. Monte Carlo simulations corroborated the experimental observations. The presented results lay the basis for the application of such metallo-supramolecular systems in advanced functional nanomaterials.

This article reviews commercially available instrumentation for inkjet printing of polymer micro-arrays for combinatorial materials research, and requirements thereof. These include a print head positioning accuracy better than 10 μm and a minimum drop volume of 100 pL. Commercially available instruments that fulfill these requirements can be divided into two categories, depending on whether they receive ink from a reservoir (dispense mode) or through fluid aspiration (pipette mode). Instruments belonging to the first category are restricted to the preparation of polymer blend micro-arrays. These consist of a few substances mixed in various ratios. The other instruments can be used for the preparation of both micro-arrays of large numbers of different pure polymer compounds and polymer blend micro-arrays. Moreover, ways to mix compounds are discussed.

The characterization of metal-containing supramolecular polymers by gel permeation chromatography (GPC) or matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) is complicated because of the interaction of the charged materials with the GPC column material in the first case and fragmentation due to the applied laser energy in the latter case. In this contribution we report recent advances made for the characterization of supramolecular polymers based on terpyridine metal complexes utilizing GPC and MALDI-TOF MS. In particular for GPC analysis, the choice of solvent and additive was found to be crucial for a successful characterization. Furthermore, MALDI-TOF MS spectra of these compounds are not straightforward to interpret. Both aspects are discussed in detail with the result of a better understanding and improved analysis possibilities of the mentioned supramolecular polymers.

A parallel synthetic approach toward homogeneous atom-transfer radical polymerization of methyl methacrylate has been successfully applied by utilizing an automated synthesizer. Experimental set-up, automated parallel synthesis and purification of the polymers via a solid-phase extraction set-up, as well as online and offline measurements of the molecular weights and monomer conversion are described in detail. In addition, a comparison with conventional experiments in the laboratory is provided.

Living cationic ring-opening polymerizations of 2-ethyl-2-oxazoline and purification of the resulting polymers were performed utilizing an automated synthesizer. Eight polymers (500 mg scale) as well as 40 polymers (150 mg scale) were synthesized in parallel to investigate the reproducibility and the living character of the polymerizations. The poly(2-ethyl-2-oxazoline)s obtained such were characterized by means of ¹H NMR spectroscopy, MALDI-TOF mass spectrometry and online gel permeation chromatography.

Combinatorial techniques, parallel experimentation and high-throughput methods represent a very promising approach in order to speed up the preparation and investigation of new polymeric materials: a large variety of parameters can be screened simultaneously resulting in new structure/property relationships. The field of polymer research seems to be perfectly suited for parallel and combinatorial methods due to the fact that many parameters can be varied during synthesis, processing, blending as well as compounding. In addition, numerous important parameters have to be investigated, such as molecular weight, polydispersity, viscosity, hardness, stiffness and other application-specific properties. A number of corresponding high-throughput techniques have been developed in the last few years and their introduction into the commercial market further boosted the development. These combinatorial approaches can reduce the time-to-market for new polymeric materials drastically compared to traditional approaches and allow a much more detailed understanding of polymers from the macroscopic to the nanoscopic scale. Here we provide an overview of the present status of combinatorial and parallel polymer synthesis and high-throughput screening.

Starting in biochemistry and pharmaceutical chemistry, combinatorial methods, automated synthesis and high-throughput characterization are being further developed for organic synthesis and polymer research. The development is strongly driven by the achievements in biochemistry and pharmaceutical chemistry and the need to minimize the time-to-market for novel polymeric products. The success of high-throughput methodologies in polymer science is partially limited by the commercially available hardware (synthesizers, workstations, robots, online-characterization instruments, etc.) and software. A short overview of commercially available equipment for polymer research is provided in this Review.

The application of automated parallel synthesizer robots for the investigation of polymerization processes is of major interest at present. In this contribution we describe the application of the emulsion polymerization of styrene and vinyl acetate. The preparations of emulsions and latexes were investigated in detail and compared to “conventional” stirred tank reactors. In particular the influence of the vortex mixing as well as the limitations regarding solid content and reactor fouling are addressed.

A systematic investigation into the surface properties of siloxane rubber/carbon black (CB) nanocomposites has been performed, using an automated scanning probe microscope. In this way the influence of CB concentration and curing rate of the siloxane rubber matrix on roughness and conductivity of the composites was studied. Decreasing the curing rate while keeping the CB concentration resulted in a decrease in both roughness and surface conductivity, which can be explained by an additional siloxane-rubber layer formed during curing.

Sixteen parallel polymerization reactions of 2-ethyl-2-oxazoline have been performed at different temperatures in an automated synthesizer that allowed individual heating of each reactor. During the reactions samples were taken automatically, which were characterized by means of both online GPC and offline GC, in order to optimize the reaction temperature and to determine the activation energy of the polymerization.

The functionalization of polystyrene/poly(ethylene glycol) TentaGel® microbeads (d = 20 μm) with 2,2′:6′,2″-terpyridine units is described resulting in a material with easily accessible ligands which possess an excellent affinity for transition metal ions. The subsequent loading with different metal ions via metal-to-ligand complexation yielded the corresponding Co^II, Ni^II, Fe^II, and Cu^II modified beads. The isolated materials were investigated in detail utilizing UV/vis spectroscopy, optical microscopy, atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Moreover, grafting of free terpyridine moieties via ruthenium(II)/ruthenium(III)-chemistry onto the beads is demonstrated. This opens-up new pathways for the selective modification of such microbeads and the preparation of functional materials.

2,2′:6′,2′′-Terpyridine compounds are important chelating ligands in a multitude of applications in the fields of supramolecular and macromolecular chemistry as well as electrochemistry. Therefore, a “pool” of functionalized terpyridine derivatives is essential. Classical and modern synthetic strategies towards terpyridine systems and novel functional 2,2′:6′,2′′-terpyridine compounds that originated in the last seven years are reviewed comprehensively. (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003)

The synthesis of novel functionalized 3,6-di(2-pyridyl)pyridazines via an inverse electron demand Diels−Alder reaction between the corresponding 3,6-di(2-pyridyl)-1,2,4,5-tetrazine and various alkynes is reported. The resulting 3,6-di(2-pyridyl)pyridazines were investigated using X-ray crystallography, IR spectroscopy, and NMR spectroscopy, whereby several 2D NMR spectroscopic techniques were exploited to conclusively assign all proton- and carbon-resonances. In addition, it was demonstrated that the functionalized 3,6-di(2-pyridyl)pyridazines are capable of forming [2 × 2] grid-like metal complexes with copper(I) and silver(I) ions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The well-known reaction of 4′-chloro-2,2′:6′,2′′-terpyridine with alkoxide nucleophiles leads to 4′-functionalized 2,2′:6′,2′′-terpyridines. This reaction allows the easy introduction of different functional groups onto the terpyridine at the 4′-position, i.e. opposite to the metal binding site, in one reaction step. Among the functionalized 2,2′:6′,2′′-terpyridines reported here are amines (including chiral examples), carboxylic acids, simple alkoxy-chain terpyridines with different chain lengths, and a stilbene-functionalized terpyridine. Moreover, the synthesis of two important already known substances was significantly improved. One example of a sequential functionalization of the (aminopentoxy)terpyridine with a dithiolane functionality is also reported. For two of the alkyl-chain-functionalized terpyridines, single-crystal X-ray crystallographic data were obtained. Finally, ordered monolayers of alkyl-substituted terpyridines on HOPG were visualized using STM. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Poly(ethylene oxide) of various molecular weights (M_n = 3 000, 5 200, 10 000, 16 500 g · mol⁻¹) has been modified with terpyridine end groups as building blocks for water-soluble metallo-supramolecular polymers. Metallo-supramolecular A–A homopolymers have been prepared and characterized by complexing the terpyridine units of one selected poly(ethylene oxide) (M_n = 3 000 g · mol⁻¹) with the following transition metal ions in their 2+ oxidation state: Fe, Ru, Co, Ni, Cu, Zn, and Cd. In addition, the stability of the supramolecular connection with respect to pH variations has been investigated.

In the present contribution, we synthesized linear coordination polymers based on oligo(ethylene glycol)s as well as poly(ethylene glycol)s and terpyridine ruthenium(II) complexes. The reaction conditions, e.g., solvent, concentration, were varied to obtain well-soluble, high molecular weight polymers. The resulting compounds were characterized by UV-vis and NMR spectroscopy. The viscosity of the materials was also investigated with and without salt addition. Finally, the polymers were characterized with DSC and AFM. AFM revealed a lamellar morphology.

A series of poly(methyl methacrylate) copolymers with terpyridine units in the side chains was obtained by free radical polymerization. The free terpyridine units were complexed by iron(II) and zinc(II) ions, and the complexation behavior was studied in detail, utilizing UV-vis and viscosity titration experiments. Complexation of the polymer chains could be observed, which resulted in characteristic UV-vis absorption bands and an increase in the solution viscosity. Addition of a strong competitive ligand (hydroxyethyl ethylenediaminetriacetic acid, HEEDTA) resulted in an efficient decomplexation.

Aqueous micelles have been prepared from amphiphilic supramolecular graft copolymers, in which poly(ethylene glycol) (PEG) side chains were linked to a poly(methyl methacrylate) (PMMA) backbone via ruthenium(II)-terpyridine complexes. Three different graft copolymers were investigated, in which the average number of PEG branches (constant length) and the length of the PMMA backbone were varied. The successful formation of micelles was proven by dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). A good agreement was found between TEM and AFM observations, which show polydisperse spherical micelles. The hydrodynamic diameter measured by DLS was much larger, suggesting the formation of aggregates. No substantial difference in the micellar characteristic features was found between the three investigated samples.

Two different metallo-supramolecular amphiphilic block copolymers have been synthesized, using a hydrophilic poly(ethylene oxide) block connected through a bis-(2,2′:6′2″-terpyridine–ruthenium) complex either to a hydrophobic polystyrene or to a poly(ethylene-co-butylene) block. These copolymers were used to prepare aqueous micelles. The morphological characterization of the metallo-supramolecular micelles was performed by dynamic light scattering and transmission electron microscopy. Besides individual micelles, larger structures were also observed by these two independent techniques. The larger structures were the result of aggregation of individual micelles. In addition, the influence of the ionic strength of the medium was investigated. Although the metallo-supramolecular copolymers do not contain charged blocks, the corresponding micelles behaved as polyelectrolyte-like micelles. This behaviour was attributed to the presence of NaCl ions, strongly associated to the poly(ethylene oxide) blocks. This was evidenced by transmission electron microscopy, that revealed the presence of the salt in the metallo-supramolecular micelles. Copyright © 2003 Society of Chemical Industry

Koordinationsverbindungen, die bereits im vorletzten Jahrhundert durch die klassische Komplexchemie und Koordinationslehre beschrieben wurden und seit den späten 50iger Jahren intensiv auf dem Gebiet der homogenen und heterogenen Katalyse Einsatz finden, stehen erneut im Mittelpunkt eines neuen Forschungsbereichs: der metallo-supramolekularen Chemie. Komplizierte, supramolekulare Liganden, als Weiterentwicklung einfacher einzähniger Liganden und Chelatliganden, führen auf der Basis von Selbstorganisations- und Selbsterkennungsprozessen zusammen mit koordinierenden Metallionen zu genau definierten supramolekularen Architekturen. Die Natur nutzt diese als wesentliche Funktionsträger in biologischen Systemen, z. B. den Hämoglobin-Eisen-Komplex. Diesem Vorbild folgend versucht die supramolekulare Chemie, hochkomplexe, jedoch genau definierte Geometrien, wie Helikate, Fäden, Leitern, Rechen oder Gitter präparativ herzustellen und somit neuartige Materialien mit speziellen Eigenschaften zu entwickeln. Der Metallkomplex als zentrale Einheit der neuen Verbindungsklasse kann zu „funktionalen supramolekularen Systemen” führen. Diese könnten Anwendungen auf den Gebieten der Polyelektrolyte, der Elektrochemie (elektrisch leitende Polymere und Redoxkatalysatoren) und der Photochemie (organische Solarzellen) ermöglichen.

Supramolecular structures and metal-complexes play a dominant role in the functionality of biomolecules. Taking nature as an example a major goal of metallo-supramolecular chemistry is the extension of the traditional coordination chemistry towards supramolecular architectures, utilizing complex ligand systems. Herein we describe a wide range of different geometries such as helicates, linear rod-like polymers, ladders, racks or grids, which are realized by the combination of supramolecular ligands and coordinating metal ions on the basis of self-assembly and self-recognition processes. Besides the pure beauty of the structures, the electro-, photochemical and magnetic properties of the materials might open avenues to applications as smart coatings, catalysts or optical devices.

The formation of asymmetric bis-complexes, based on terpyridine ligands and ruthenium ions, is described as a powerful tool for the self-assembly of polymer blocks end-functionalized with terpyridine units. This is illustrated in this contribution for the synthesis of amphiphilic metallo-supramolecular block copolymers, which are further used to produce aqueous micelles. Finally, the reversibility of the supramolecular bond opens new avenues for the preparation and manipulation of these nano-objects.

Diblock copolymers of poly(styrene) and poly(ethylene oxide) were prepared utilizing a bisterpyridine ruthenium complex as non-covalent interaction for the connection of the two blocks. Apart from the synthesis and characterization of four metallo-supramolecular block copolymers, first studies on the thermal properties of the block copolymers have been performed. A complex crystallization behavior was observed and is described in a qualitative fashion. The influence of the metal complex on the thermal stability of the metallo-supramolecular block copolymers remains a question for further investigation.

Here we demonstrate the synthesis of telechelics with different spacer units and different numbers of metal-complexing units, like α-methoxy-ω-(2,2′:6′,2″-terpyrid-4′-yl)-poly(ethylenoxide)₇₈ (1), bis(2,2′:6′,2″-terpyrid-4′-yl) di(ethylene glycol) (2), bis(2,2′:6′,2″-terpyrid-4′-yl)-poly(ethylene oxide)₁₈₀ (3) and tris[(2,2′:6′,2″-terpyrid-4′-yl)-oligo (ethylenoxy-)_3.33]glycerin (4) utilizing 4-chloro-2,2′:6′,2″-terpyridine. The complexation behaviour of a variety of metal-salts towards the telechelics was studied and different supramolecular architectures were investigated, such as symmetric polymeric complexes and linear coordination polymers. Furthermore, attempts have been undertaken to prepare metallo-supramolecular cross-linked systems.

In aqueous solutions, amphiphilic block copolymers in which a polystyrene (PS) segment is connected to a poly(ethylene oxide) (PEO) block via a bis(2,2′:6′,2″- terpyridine ruthenium) complex can form micelles. Such micelles of the protomer type PS₂₀-[Ru]-PEO₇₀, according to the preparation procedure representing frozen micelles, were studied by sedimentation velocity and sedimentation equilibrium analysis in an analytical ultracentrifuge and by transmission electron microscopy, with different techniques applied for the sample preparation. The particles obtained were surprisingly multifarious in size. In ultracentrifugation experiments performed at relatively low salt concentrations, the distributions of the sedimentation coefficient s_20,w showed a pronounced peak at 9.6 S and a broad, only partly separated second peak around 14 S. The molar mass of the particles at the peak was around 430,000 g/mol, corresponding to an aggregation number of approximately 85. The average hydrodynamic diameter of the particles in the peak fraction was approximately 13 nm. In electron micrographs of negatively stained samples, spheres of diameters between 10 and 25 nm were the most abundant particles, but larger ones with a wide size range were also visible. The latter particles apparently were composed of smaller ones. The data from both sedimentation analysis and electron microscopy showed that (1) the studied compound formed primary micelles of diameters around 20 nm and (2) the primary micelles had a tendency toward aggregation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3159–3168, 2003

Commercially available poly(vinyl chloride) (PVC) was covalently modified with terpyridine supramolecular binding units in a two-step reaction. First, PVC was modified with aromatic thiols to introduce OH functionalities into the polymer backbone, which were subsequently reacted with an isocyanate-functionalized terpyridine binding unit. The resulting functionalized material contained metal-ion binding sites, which could be used for grafting and crosslinking reactions. A grafting experiment was performed with a small organic terpyridine ligand. The complexation of the modified PVC with several transition-metal ions was studied with ultraviolet–visible spectroscopy and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2964–2973, 2003

The application of automated synthetic parallel methods in polymer chemistry is described. A brief overview of all different polymerization techniques that have been used is provided. Furthermore, the equipment and methodologies that were used in our approach for automated parallel polymerization reactions are discussed followed by detailed insight into recent developments on automated cationic ring-opening polymerization, atom transfer radical polymerization, and emulsion polymerizations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2425–2434, 2003

Several synthetic strategies for the incorporation of supramolecular binding units into polymers are described. Specifically, terpyridine ligands have been introduced into polymers in such a way that they are distributed either randomly throughout the polymer backbone or at the chain end(s). Two terpyridine ligands form octahedral complexes with a variety of transition-metal ions, each having different properties. Some general statements regarding metal complex stability are presented as well as a special case representing the selective construction of heteroleptic terpyridine complexes. This leads to a kind of LEGO system for connecting and disconnecting the polymer blocks via metal complexes. Metallo-supramolecular block copolymers, graft copolymers, and chain-extended polymers can be designed and prepared with the principles described. Once the design parameters have been derived, thorough control over the final material and its properties can be gained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1413–1427, 2003

The luminescent complex [4-(3-hydroxypropyl)-4′-methyl-2,2′-bipyridine]-bis(2,2′-bipyridine)-ruthenium(II)-bis(hexafluoroantimonate) and its methacrylate derivative were successfully synthesized and fully characterized by two-dimensional ¹H and ¹³C{¹H} NMR techniques [correlation spectroscopy (COSY) and heteronuclear multiple-quantum coherence experiment (HMQC)], as well as matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The respective labeled methyl methacrylate-ruthenium(polypyridyl) copolymers were obtained by free-radical copolymerization with methyl methacrylate and were characterized utilizing NMR, IR, and UV–visible spectroscopy and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3954–3964, 2003

Bis(2,2′:6′,2″-terpyrid-4′-yl) diethylene glycol was synthesized as a monomer unit and further utilized for polymerization with FeCl₂ in order to form water-soluble coordination polymers. Viscosity measurements and film-forming properties indicate the formation of linear coordination polymers or larger ring structures. The terpyridine/iron(II) complexes are stable up to temperatures of 210 °C, but can be uncomplexed by the addition of an excess of a strong competitive ligand (HEDTA) under mild conditions.

An amphiphilic metallo-supramolecular poly(ethylene-co-butylene)-block-poly(ethylene oxide) diblock copolymer containing a bis(2,2′:6′,2″-terpyridine)ruthenium(II) complex as a supramolecular connection between the two constituting blocks was used to prepare stable aqueous micelles. The micelles were characterized by dynamic light scattering and atomic force microscopy. Individual micelles were observed together with aggregates of micelles. Only the addition of a large excess of competitive ligand caused the cleavage of the very stable ruthenium complex.

A copolymer of poly(methyl methacrylate) with terpyridine units in the side chains was synthesized utilizing free-radical polymerization. The free terpyridine units were complexed with several different terpyridineruthenium mono-complexes, yielding metallo-supramolecular graft copolymers. The materials obtained were characterized by means of NMR and UV-vis spectroscopy as well as GPC. Characterization by thermal analysis revealed distinct differences between these new materials and the initial copolymer.

The ability of a broad range of N-heterocycles to act as very effective and stable complexation agents for several transition metal ions, such as cobalt(II), copper(II), nickel(II), and ruthenium(II), has long been known in analytical chemistry. This behavior was later utilized in supramolecular chemistry for the construction of highly sophisticated architectures, such as helicates, racks, and grids. The discovery of macromolecules by Staudinger in 1922 opened up avenues towards sophisticated materials with properties hitherto completely unknown. In the last few decades, the combination of macromolecular and supramolecular chemistry has been attempted by developing metal-complexing and metal-containing polymers for a wide variety of applications that range from filtration to catalysis. The stability of the polymer–metal complex is a fundamental requirement for such applications. In this respect, the use of bi- and terpyridines as chelating ligands is highly promising, since these molecules are known to form highly stable complexes with interesting physical properties with transition-metal ions. A large number of different structures have been designed for many different applications, but polymers based on the application of coordinative forces have been prepared in a few cases only. Furthermore, the synthetic procedures applied frequently resulted in low yields. During the last few years, strong efforts have been made in the direction of self-assembling and supramolecular polymers as novel materials with “intelligent” and tunable properties. In this review, an overview of this active area at the interface of supramolecular and macromolecular chemistry is given.

The cover picture shows the molecular modeling of a star-shaped metallo-supramolecular polymer and the schematic drawing of a linear analogue. These molecules are of great interest because of their unique properties. Metallo-supramolecular polymers emerge by the well-directed combination of polymers, the properties of which have dominated the development of materials in recent years, with supramolecular ligands, which have the ability to organize spontaneously and form unique structures on a molecular level, and transition-metal ions, which, through their physical properties bring characteristic functionalities. The well-known properties of the individual components allow the use of established methods, such as UV/Vis spectroscopy, NMR spectroscopy, and gel permeation chromatography for characterization. However, the combination also requires the application of new methods, such as analytical ultracentrifugation or MALDI-TOF mass spectrometry. More about metallo-supramolecular polymers based on bipyridine and terpyridine complexes can be found in the review by U. S. Schubert and C. Eschbaumer on p. 2892 ff.

Metallo-supramolekulare AB-Blockcopolymere sind die ersten Beispiele für ein neues Konzept zur Herstellung von Blockcopolymeren. Hierfür werden unsymmetrische Bis(terpyridin)-Ruthenium-Komplexe als supramolekulare Verknüpfung zwischen zwei Blöcken verwendet (siehe Schema).

Die Fähigkeit von Stickstoffheterocyclen, Übergangsmetallionen wie Cobalt(II), Kupfer(II), Nickel(II) und Ruthenium(ii) außerordentlich effektiv und stabil zu komplexieren, wird schon seit langem in der Analytischen Chemie angewendet. In der Supramolekularen Chemie nutzte man später diese Eigenschaft zum Aufbau anspruchsvoller Strukturen wie Helicate, Leitern oder Gitter. Die Entdeckung der Makromoleküle durch Staudinger eröffnete bereits 1922 den Zugang zu einer Materialklasse mit bis dahin völlig unbekannten Eigenschaften. Erst in den letzten Jahrzehnten jedoch wurde versucht, die Makromolekulare und Supramolekulare Chemie durch die Entwicklung von metallkomplexierenden und metallhaltigen Polymeren mit Anwendungen von der Filtration bis zur Katalyse zu vereinen. Die entscheidende Anforderung an Materialien für solche Anwendungen ist die Stabilität der Polymer-Metallkomplexe. Besonders vielversprechend ist die Verwendung der mehrzähnigen Bipyridin- und Terpyridin-Chelatliganden, die sehr stabile Übergangsmetallkomplexe mit beeindruckenden physikalischen Eigenschaften bilden. Ein breites Spektrum an Strukturen ist für eine ebenso umfangreiche Zahl von Anwendungen entwickelt worden. Die Synthese von Polymeren auf Basis koordinativer Wechselwirkungen wurde dagegen bis vor wenigen Jahren nur in sehr wenigen Fällen realisiert und führte darüber hinaus häufig zu geringen Ausbeuten. In den vergangenen Jahren jedoch erlebte die Forschung zu selbstorganisierten und supramolekularen Polymeren als neue, „intelligente“ Materialien mit einstellbaren Eigenschaften einen Höhenflug. In diesem Aufsatz geben wir einen Überblick über dieses Gebiet an der Schnittstelle von Supramolekularer und Makromolekularer Chemie.

Das Titelbild zeigt das Molecular Modeling eines sternförmigen sowie die schematische Darstellung eines linearen metallo-supramolekularen Polymers. Diese Moleküle sind wegen ihrer einzigartigen Eigenschaften für Werkstoffe von größtem Interesse. Metallo-supramolekulare Polymere entstehen durch gezielte Kombination von Polymeren, deren Materialeigenschaften die Werkstoffentwicklung der vergangenen Jahre dominierten, mit supramolekularen Liganden, deren Fähigkeit zur spontanen Selbstorganisation neuartige Strukturen auf molekularer Ebene entstehen lässt, und Übergangsmetallionen, deren physikalische Eigenschaften charakteristische Funktionalitäten einbringen. Die Eigenschaften der Einzelkomponenten ermöglichen die Charakterisierung mit etablierten Methoden wie UV/Vis-Spektroskopie, NMR-Spektroskopie und Gelpermeationschromatographie. Die Kombination erfordert jedoch auch die Anwendung neuer Methoden wie analytische Ultrazentrifugation oder MALDI-TOF-Massenspektrometrie. Mehr zu metallo-supramolekularen Polymeren auf der Basis von Bipyridin- und Terpyridinkomplexen erfahren Sie im Aufsatz von U. S. Schubert und C. Eschbaumer auf S. 3016 ff.

Metallo-supramolecular AB block copolymers are the first examples of macromolecular engineeering. A new concept for the formation of block copolymers by a supramolecular approach is presented. For this purpose the authors utilized an asymmetrical bis(terpyridine)–ruthenium complex as the supramolecular linkage between the two blocks (see figure).

Mono- and difunctionalized 6,6′-dimethyl-2,2′-bipyridines were introduced into polyesters in order to design polymer architectures with specific metal binding units. The polymerizations were carried out using aluminium-alkoxide derivatives prepared by a reaction between triethylaluminium and the corresponding hydroxymethyl-functionalized bipyridine derivatives. Polymers with narrow molecular weight distribution were obtained. The incorporation of the metal binding unit could be proven by UV/VIS-spectroscopy and NMR-spectroscopy.

Chiral polyesters, end-capped with terpyridine, were prepared via the coordinative ring-opening polymerization of L-lactide. Stable supramolecular dimer structures resulted after complexation with iron(II) ions. The formation of both the macroligands and the polymer complexes was proven for the first time clearly by means of GPC coupled to an in-line photodiode array UV/Vis spectrophotometer, NMR spectroscopy and MALDI-TOF mass spectrometry. A sensitivity of the iron(II)-centered poly(L-lactide)s towards UV irradiation and thermal or pH changes could be observed.

A series of dipyridylamine and terpyridine derivatives, norborn-2-ene-5-di(pyrid-2-yl)carbamide (1), 4′-(norborn-2-ene-5-ylmethyleneoxy)terpyridine (2), di-(pyrid-2-yl)acetamide (3) and bis(4′-(norborn-2-ene-5-ylmethyleneoxy)-2,2′:6′,2″-terpyridine)iron(II) hexafluorophosphate (4) have been synthesized. Linear homopolymers, poly-1 and poly-2, as well as grafted and coated silica- and PS-DVB-based polymer supports have been prepared therefrom via ring-opening metathesis polymerization (ROMP). Monomer 3, poly-1, poly-2 have been loaded with Cu (I), Cu (II), Fe (II) as well as Hg (II) salts, respectively. These metal complexes as well as metal loaded supports based on compounds 1, 2 and 4 have subsequently been used for homogeneous and heterogeneous atom-transfer radical polymerization (ATRP) of styrene. Systems based on poly-2 coated silica loaded with Cu (I) were found to work best. Under optimum conditions, polystyrene was obtained in 30% yield with polydispersity indices < 1.6 within 2 h and with a remaining metal content in the ng/g (ppb)-range.

Polymeric materials containing coordinative units have become a field of increasing interest. The combination of inorganic metal-containing units and macromolecules leads to supramolecular structures with new properties. One promising approach to such systems is the application of metallo-supramolecular initiators for living and controlled polymerization methods. The utilization of bi- and terpyridine units and complexes for this purpose will be discussed in this article.