A fragmentable support material for Ziegler–Natta catalysts is presented based on micrometer-sized aggregates of polystyrene nanoparticles. Hydroxyl anchoring groups are introduced by copolymerization of hydroxymethylstyrene in emulsion process to immobilize the catalysts. The catalytic activity in ethylene slurry polymerizations is found to be directly correlated to the hydroxyl group content of the supports. Furthermore, the fragmentation behavior of dye-labeled support aggregates into the initial nanoparticles is demonstrated using laser scanning confocal fluorescence microscopy as a nondestructive method. These supported catalysts fulfill two important design criteria, high fragmentability and high catalyst loading, and produce high-density polyethylene with medium molecular weight distributions (MWDs = 3–4). These values lie between those obtained using single-site metallocene-based (narrow MWD < 3) or inorganic supported multi-site Ziegler–Natta-based (broad MWD = 4–12) polymerizations without the need of blending. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 15–22

A versatile nanoparticle system is presented in which drug release is triggered by enzymatic polymer cleavage, resulting in a physicochemical change of the carrier. The polylactide-block-peptide-block-polylactide triblock copolymer is generated by initiation of the ring-opening polymerization of L-lactide with a complex bifunctional peptide having an enzymatic recognition and cleavage site (Pro-Leu-Gly-Leu-Ala-Gly). This triblock copolymer is specifically bisected by matrix metalloproteinase-2 (MMP-2), an enzyme overexpressed in tumor tissues. Triblock copolymer nanoparticles formed by nonaqueous emulsion polymerization are readily transferred into aqueous media without aggregation, even in the presence of blood serum. Cleavage of the triblock copolymer leads to a significant decrease of the glass transition temperature (T_g) from 39 °C to 31 °C, likely mediating cargo release under physiological conditions. Selective drug targeting is demonstrated by hampered mitosis and increased cell death resulting from drug release via MMP-2 specific cleavage of triblock copolymer carrier. On the contrary, nanocarriers having a scrambled (non-recognizable) peptide sequence do not cause enhanced cytotoxicity, demonstrating the enzyme-specific cleavage and subsequent drug release. The unique physicochemical properties, cleavage-dependent cargo release, and tunability of carrier bioactivity by simple peptide exchange highlight the potential of this polymer-nanoparticle concept as platform for custom-designed carrier systems.

Proton-conducting networks (NETs) were prepared successfully by the insertion of phosphonated nanochannels into organic–inorganic hybrid materials that contain Al³⁺ as the connector and hexakis(p-phosphonatophenyl)benzene (HPB) as the linker. Noncomplexed phosphonic acid groups remain in the framework, which depends on the ratio of both compounds, to yield a proton conductivity in the region of 10⁻³ S cm⁻¹. This conductivity can be further improved and values as high as Nafion, a benchmark proton-exchange membrane for fuel cell applications, can be obtained by filling the network pores with intrinsic proton conductors. As a result of their sponge-like morphology, aluminum phosphonates adsorb conductive small molecules such as phosphonic acids, which results in a very high proton conductivity of approximately 5×10⁻² S cm⁻¹ at 120 °C and 50 % relative humidity (RH). Contrary to Nafion, the doped networks show a remarkably low temperature dependence of proton conductivity from external humidification. This effect indicates a transport mechanism that is different to the water vehicle mechanism. Furthermore, the materials exhibit an activation energy of 40 kJ mol⁻¹ at 15 % RH that starts to diminish to 10 kJ mol⁻¹ at 80 % RH, which is even smaller than the corresponding values obtained for Nafion 117.

Monodisperse, molecularly imprinted nanospheres were synthesized by nonaqueous (mini)emulsion polymerization using a standard monomer mixture of methacrylic acid and ethylene dimethacrylate containing the drug propranolol as a template. The preparation conditions (solvent, amount of surfactant, and amount of employed template) were extensively varied in order to assess their effect on the properties of the resulting polymer nanoparticles. The molecular recognition capability of the nanospheres was evaluated in batch rebinding experiments, and the effect of the nanosphere preparation conditions as well as of the reaction conditions was investigated. In this way, optimal preparation protocols for molecularly imprinted nanoparticles under nonaqueous conditions with the use of a nonionic emulsifier were identified, which lead to nanospheres with a diameter of around 100 nm having an enhanced capacity of specific template rebinding compared to both nonimprinted nanospheres and to particles obtained by emulsion polymerization in water. Best results were obtained with nanospheres prepared in N,N-dimethylformamide/n-hexane with a high functional monomer to template ratio. The enantioselectivity of the rebinding process was also demonstrated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Block copolymers containing poly(phenylene oxide) (PPO) and poly(vinyl benzyl phosphonic acid) segments are synthesized via atom transfer radical polymerization (ATRP). Monofunctional PPO blocks are converted into ATRP active macroinitiators, which are then used to polymerize a diethyl p-vinylbenzyl phosphonate monomer in order to obtain phosphonated block copolymers bearing pendent phosphonic ester groups. Poly(phenylene oxide-b-vinyl benzyl phosphonic ester) block copolymers are hydrolyzed to corresponding acid derivatives to investigate their proton conductivity. The effect of the relative humidity (RH) is investigated. The proton conductivity at 50% RH and one bar of vapor pressure approaches 0.01 S cm⁻¹.

The preparation of poly(L-lactide) nanoparticles via ring-opening polymerization (ROP) of L-lactide is conducted in non-aqueous emulsion. In this process, acetonitrile is dispersed in either cyclohexane or n-hexane as the continuous phase and stabilized by a PI-b-PEO, respectively, a PI-b-PS copolymer as emulsifier. The air and moisture sensitive N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-2-ididazolidinylidene (SIMes) catalyzes the polymerization of L-lactide at ambient temperatures. Spherical poly(L-lactide) nanoparticles with an average diameter of 70 nm and a tunable molecular weight are generated. Hence, the non-aqueous emulsion technique demonstrates its good applicability toward the generation of well-defined poly(L-lactide) nanoparticles under very mild conditions.

Organic proton-conducting molecules are presented as alternative materials to state-of-the-art polymers used as electrolytes in proton-exchanging membrane (PEM) fuel cells. Instead of influencing proton conductivity via the mobility offered by polymeric materials, the goal is to create organic molecules that control the proton-transport mechanism through supramolecular order. Therefore, a series of phosphonic acid-containing molecules possessing a carbon-rich hydrophobic core and a hydrophilic periphery was synthesized and characterized. Proton conductivity measurements as well as water uptake and crystallinity studies (powder and single-crystal X-ray analysis) were performed under various conditions. These experiments reveal that proton mobility is closely connected to crystallinity and strongly dependent on the supramolecular ordering of the compound. This study provides insights into the proton-conducting properties of this novel class of materials and the mechanisms responsible for proton transport.

Two synthetic approaches to modify the surface of inorganic particles are presented. In the first approach the inorganic particles are prepared in-situ in a confined space in inverse emulsions. The used amphiphilic statistical copolymers act not only as emulsifiers, but they also hydrophobize the remaining inorganic particles after the precipitation. This approach represents a versatile method to obtain various inorganic nanoparticles as well as more complex inorganic materials like core-multiple shell and perovskite-based nanoparticles. The second procedure uses preformed inorganic particles, as an aqueous dispersion, to modify them with surface active amphiphilic copolymers in a multicomponent solvent system. This method turns out to be a simple but highly efficient method to modify preformed inorganic nanoparticles. The particles are characterized by SEM, TEM and dynamic light scattering. The modified inorganic nanoparticles are suitable to be homogenously incorporated into a polymer matrix to form transparent nanocomposite materials.

Summary: The preparation of functional polymer latex particles is usually carried out in aqueous heterogeneous systems, i.e. for example in emulsion or mini-emulsion polymerization. Due to the presence of water, moisture sensitive reactions like step growth polymerizations or metal catalyzed reactions can not be accomplished without side reactions and / or decomposition. In order to avoid these side reactions, different nonaqueous emulsion systems have been developed. According to the desired polymerization procedure, these systems consist of a nonpolar organic phase surrounded by a perfluorinated solvent or of a polar organic phase which is dispersed in a nonpolar organic solvent. Both emulsions are stabilized by amphipolar block copolymers and result in long time stable particle dispersions. The resulting dispersions yield particles with narrow size distributions and – depending on the reaction conditions – diameters down to tens of nanometers. This technique allows the formation of particles consisting of numerous different classes of polymers, e.g. polyurethanes, polyesters, polyolefins etc. and the formation of more complex morphologies such as core shell structures.

As an alternative to inorganic supports, emulsions and organic carriers were developed for metallocene-catalyzed polyolefin synthesis in the last years. Oil-in-oil emulsions based on a perfluorinated solvent provide the possibility to synthesize polymer particles on the nanometer length scale, while the latex particles consisting of polystyrene with different surface functionalities yield particles on the micrometer range. To obtain a deeper insight to the reaction course of both techniques and to the product morphology and fragmentation behavior of the organic carriers, substantial information concerning the kinetics of these reactions is crucial. Thus, standard analytical methods were combined with real-time video microscopy and laser scanning fluorescence microscopy (LSCFM) of perylene labeled particles for improving these methods for polyolefin synthesis.