Theo J. Dingemans

ABSTRACTA series all-aromatic poly(esterimide)s with different molar ratios of N-(3′-hydroxyphenyl)-trimellitimide (IM) and 4-hydroxybenzoic acid (HBA) (IM/HBA = 0.3/0.7 and 0.7/0.3) was prepared with the aim to design flexible high Tg films. Melt-pressed films, either from high molecular weight polymer or cured phenylethynyl precursor oligomers, exhibit Tgs in the range of 200 °C to 242 °C and are brittle. After a thermal stretching procedure, the films became remarkably flexible and very easy to handle. In addition, the thermally stretched 3-IM/7-HBA and 7-IM/3-HBA films show tensile strengths of 108 MPa and 169 MPa, respectively. Thermal treatment increased the Tg of 3-IM/7-HBA from 205 °C to 248 °C, whereas the Tg of 7-IM/3-HBA increased from 230 °C to 260 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44774.

Molecular ordering in the high-temperature nematic phase of an all-aromatic liquid crystal

Co-reporter:Francesco Vita, Maruti Hegde, Giuseppe Portale, Wim Bras, Claudio Ferrero, Edward T. Samulski, Oriano Francescangeli and Theo Dingemans

Soft Matter 2016 vol. 12(Issue 8) pp:2309-2314

Publication Date(Web):19 Jan 2016

DOI:10.1039/C5SM02738A

We report the structural characterization of the nematic phase of 2,6-biphenyl naphthalene (PPNPP). This lath-like all-aromatic mesogen provides a valuable benchmark for classical theories of nematic order. PPNPP exhibits a very high temperature nematic phase (417–489 °C) above an enantiotropic smectic A phase. X-ray diffraction reveals a surprisingly strong tendency towards molecular layering in the nematic phase, indicative of “normal cybotaxis” (i.e. SmA-like stratification within clusters of mesogens). Although stronger at low temperatures, the layering is evident well above the smectic A-nematic transition. The nematic order parameter is evaluated as a function of temperature from the broadening of the wide-angle diffuse diffraction feature. Measured values of the orientational order parameter are slightly larger than those predicted by the Maier–Saupe theory over the entire nematic range except for a narrow region just below the clearing point where they significantly drop below the theoretical prediction.

Charge transport through conjugated azomethine-based single molecules for optoelectronic applications

Co-reporter:M. Koole, R. Frisenda, M.L. Petrus, M.L. Perrin, H.S.J. van der Zant, T.J. Dingemans

Organic Electronics 2016 Volume 34() pp:38-41

Publication Date(Web):July 2016

DOI:10.1016/j.orgel.2016.03.043

•The conductance of an azomethine based molecule is determined using the mechanically controlled breakjunction technique.•A 3-ring azomethine-based molecule has a conductance comparable to its vinyl-based analogue.•The bulk mobility of azomethine based organic electronics does not appear to be limited by intra-molecular charge transport.The single-molecule conductance of a 3-ring, conjugated azomethine was studied using the mechanically controlled breakjunction technique. Charge transport properties are found to be comparable to vinyl-based analogues; findings are supported with density functional calculations. The simple preparation and good transport properties make azomethine-based molecules an attractive class for use in polymer and single-molecule organic electronics.

All-Aromatic (AB)n-Multiblock Copolymers via Simple One-Step Melt Condensation Chemistry

Co-reporter:Qingbao Guan, Ben Norder, Liangyong Chu, Nicolaas A. M. Besseling, Stephen J. Picken, and Theo J. Dingemans

Macromolecules 2016 Volume 49(Issue 22) pp:8549-8562

Publication Date(Web):November 2, 2016

DOI:10.1021/acs.macromol.6b01341

We have prepared (AB)n-multiblock copolymers based on N-(3′-hydroxyphenyl)trimellitimide (IM), 4-hydroxybenzoic acid (HBA), and 6-hydroxy-2-naphthoic acid (HNA) via a simple one-pot melt condensation method. The blocky nature is the result of phase separation taking place in the early stages of the melt polymerization process. The liquid crystal HBA/HNA fraction phase separates from the isotropic HBA/IM fraction and this phase separation effectively shuts down transesterification reactions, preventing randomization of the polymer backbone. The (AB)n-multiblock copoly(esterimide)s exhibit two distinct glass transition temperatures (Tgs). The first Tg at ∼120 °C can be assigned to the HBA/HNA rich A-block and the second Tg at ∼220 °C can be assigned to the HBA/IM rich B-block. When introducing imide-based phenylethynyl end-groups, these reactive functionalities end-up exclusively at the termini of the HBA/IM rich B-blocks, effectively forming a phenylethynyl-terminated B(AB)n-reactive oligomer. Upon thermal treatment, cross-linking via the phenylethynyl end-groups results in a thermoset where the Tg of the B-block increases by as much as ∼106 °C. The Tg of the HBA/HNA A-block remains unchanged. Scanning electron microscopy experiments show a gradual change in morphology, from a typical fibrous LCP texture for the HBA/HNA rich polymers to a more consolidated morphology for the HBA/IM rich polymers. Atomic force microscopy images confirm the presence of two distinct domains when 44 mol % of HBA was replaced by IM. The “hard” imide rich B-blocks form domains of ∼100–200 nm that are embedded in the imide poor or “soft” A-blocks.

Device Performance of Small-Molecule Azomethine-Based Bulk Heterojunction Solar Cells

Co-reporter:Michiel L. Petrus, Frederik S. F. Morgenstern, Aditya Sadhanala, Richard H. Friend, Neil C. Greenham, and Theo J. Dingemans

Chemistry of Materials 2015 Volume 27(Issue 8) pp:2990

Publication Date(Web):March 29, 2015

DOI:10.1021/acs.chemmater.5b00313

Recently, we demonstrated that small-molecule azomethines are promising candidates as electron-donating materials for organic photovoltaic (OPV) devices. Azomethines can be prepared via well-known condensation chemistry, with water being the sole byproduct. Here we present a record power conversion efficiency for azomethine-based small-molecule OPV devices of 2.2%. To understand the underlying physics limiting device performance, devices of the small-molecule azomethine TPA–TBT–TPA were characterized using a range of spectroscopic and electro-optical techniques. Light-intensity-dependent current-density measurement showed the presence of nongeminate charge recombination, which is most likely the result of poor charge mobility. In addition, transient absorption measurements showed a relatively short lifetime for the exciton (120 ps). However, due to the very fast charge dissociation (<300 fs), charge separation is relatively efficient. This knowledge presents a guideline for preparing subsequent generations of compounds with improved device performance.

Correction: A low cost azomethine-based hole transporting material for perovskite photovoltaics

Co-reporter:M. L. Petrus, T. Bein, T. J. Dingemans and P. Docampo

Journal of Materials Chemistry A 2015 vol. 3(Issue 32) pp:16874-16874

Publication Date(Web):28 Jul 2015

DOI:10.1039/C5TA90163D

A low cost azomethine-based hole transporting material for perovskite photovoltaics

Co-reporter:M. L. Petrus, T. Bein, T. J. Dingemans and P. Docampo

Journal of Materials Chemistry A 2015 vol. 3(Issue 23) pp:12159-12162

Publication Date(Web):11 May 2015

DOI:10.1039/C5TA03046C

Most hole transporting materials (HTMs) prepared for perovskite solar cell applications are synthesized via cross-coupling reactions that require expensive transition metal catalysts, inert reaction conditions and extensive product purification; making large-scale production cost-prohibitive. Here, we describe the synthesis of a simple azomethine-based conjugated small-molecule (EDOT-OMeTPA) which is easily prepared in a cost effective Schiff base condensation reaction, with water being the only by-product. As the hole transporter in planar CH3NH3PbI3 perovskite solar cells, efficiencies exceeding 11% were reached. This result is comparable to state-of-the-art materials such as Spiro-OMeTAD on a like-to-like comparison, while cost estimations show that the material cost is about one order of magnitude lower for EDOT-OMeTPA, resulting in a negligible cost-per-peak-Watt contribution of 0.004 $ W−1. In addition, the high synthetic accessibility of EDOT-OMeTPA also reduces the toxic chemical waste and therefore greatly reduces its environmental impact. Our results pave the way towards low-cost, environmentally friendly and efficient HTMs.

Water and sodium transport and liquid crystalline alignment in a sulfonated aramid membrane

Co-reporter:Jianwei Gao, Ying Wang, Ben Norder, Santiago J. Garcia, Stephen J. Picken, Louis A. Madsen, Theo J. Dingemans

Journal of Membrane Science 2015 Volume 489() pp:194-203

Publication Date(Web):1 September 2015

DOI:10.1016/j.memsci.2015.03.090

•Crosslinkable membranes based on a liquid crystal sulfonated aramid (PBDT).•In-plane LC order results in high in-plane diffusion coefficients for water and Na+.•PBDT chains form nano-scale hydrophilic channels.Two sulfonated aramids, poly(2,2′-disulfonylbenzidine terephthalamide) (PBDT) and poly(2,2′-disulfonylbenzidine isophthalamide) (PBDI), were synthesized with the aim to explore their unique morphology for proton exchange membrane applications. Due to the different polymer structures, PBDT forms a nematic liquid crystal, whereas PBDI is isotropic. Both polymers show excellent thermal stabilities (Td5%>400 °C), high storage moduli (E′=3–15 GPa) and crosslinked films are flexible and easy to handle. Pulsed-field-gradient NMR diffusometry reveals that the in-plane water diffusion in the nematic PBDT membrane is as high as 3.3×10−10 m2/s, whereas the diffusion in amorphous PBDI is only 2.5×10−10 m2/s. Whereas neat and crosslinked PBDI shows isotropic diffusion, neat PBDT shows a high diffusion anisotropy (D∥/D⊥=3.0), which increases as a function of crosslink density (D∥/D⊥=4.6 at 80% crosslinking). This diffusion anisotropy is substantially higher than that typically observed for low molecular weight liquid crystals and for oriented polymeric conductors such as Nafion® (D∥/D⊥~2.0). The nematic order in the PBDT membrane also promotes directed ionic conductivity, i.e. Na+ conductivity in PBDT is 2.24×10−2 S/cm and 1.67×10−2 S/cm for PBDI, respectively. We propose that the rigid-rod PBDT chains form nano-scale hydrophilic channels, which act as pathways for transporting water molecules and ions.

Gas transport in metal organic framework–polyetherimide mixed matrix membranes: The role of the polyetherimide backbone structure

Co-reporter:Maruti Hegde, Salman Shahid, Ben Norder, Theo J. Dingemans, Kitty Nijmeijer

Polymer 2015 Volume 81() pp:87-98

Publication Date(Web):16 December 2015

DOI:10.1016/j.polymer.2015.11.002

We report on how the morphology of the polymer matrix, i.e. amorphous vs. semi-crystalline, affects the gas transport properties in a series of mixed matrix membranes (MMMs) using Cu3(BTC)2 as the metal organic framework (MOF) filler. The aim of our work is to demonstrate how incorporation of Cu3(BTC)2 affects the polyetherimide matrix morphology and thereby highlighting the importance of selecting the appropriate polyetherimide matrix for mixed matrix membranes.We used three amorphous poly(etherimide)s with very similar backbone structures. Polyetherimide ODPA-P1 was used as a linear flexible matrix, aBPDA-P1 is a non-linear rigid matrix and 6FDA-P1 was selected because the backbone structure is similar to ODPA-P1 but replacing the oxygen linker with two bulky –CF3 groups results in a linear polymer with a low chain packing efficiency. Using an in-situ polymerization technique, up to 20 wt.% Cu3(BTC)2 could be homogenously dispersed in all three PEIs. The ODPA-P1 matrix crystallized when Cu3(BTC)2 was introduced as a filler. Gas permeation studies were performed by analyzing membrane performance using a 50:50 CO2:CH4 mixed gas feed. The presence of crystalline domains in ODPA-P1 resulted in a decrease in permeability for both CO2 and CH4 but the selectivity increased from 41 to 52 at 20 wt.% Cu3(BTC)2. The non-linear, rigid, aBPDA-P1 matrix remains amorphous when Cu3(BTC)2 is introduced. SEM images of the MMM cross-section revealed a sieve-in-a-cage morphology and at 20 wt.% Cu3(BTC)2, the permeation of both CO2 and CH4 increased by 68% thereby negating any change in selectivity. For 6FDA-P1 with 20 wt.% Cu3(BTC)2, only the permeability of CO2 increased by 68% resulting in an increase in selectivity of 33%.

Small-molecule azomethines: organic photovoltaics via Schiff base condensation chemistry

Co-reporter:M. L. Petrus, R. K. M. Bouwer, U. Lafont, S. Athanasopoulos, N. C. Greenham and T. J. Dingemans

Journal of Materials Chemistry A 2014 vol. 2(Issue 25) pp:9474-9477

Publication Date(Web):08 May 2014

DOI:10.1039/C4TA01629G

Conjugated small-molecule azomethines for photovoltaic applications were prepared via Schiff base condensation chemistry. Bulk heterojunction (BHJ) devices exhibit efficiencies of 1.2% with MoOx as the hole-transporting layer. The versatility and simplicity of the chemistry is illustrated by preparing a photovoltaic device directly from the reaction mixture without any form of workup.

Correlating on-substrate prepared electrochromes with their solution processed counterparts – towards validating polyazomethines as electrochromes in functioning devices

Co-reporter:Michael E. Mulholland, Daminda Navarathne, Michiel L. Petrus, Theo J. Dingemans and W. G. Skene

Journal of Materials Chemistry A 2014 vol. 2(Issue 43) pp:9099-9108

Publication Date(Web):08 Aug 2014

DOI:10.1039/C4TC01003E

A series of polyazomethines prepared from complementary triphenylamine diamines and thiophene dialdehydes by both solution step-growth and on-substrate polymerizations were examined. The absorbance, electrochemical, and spectroelectrochemical properties of the solution processable polyazomethines were compared to their on-substrate prepared counterparts that were immobilized on ITO coated glass substrates. The on-substrate prepared polymers were found to have enhanced optical and spectroelectrochemical properties compared to their solution processed counterparts. The optoelectronic properties were also contingent on the substitution of the triphenylamine repeating unit with electron donating and withdrawing groups. The on-substrate prepared polyazomethines offered many advantages compared to their counterparts prepared by conventional solution step-growth polymerization, including shorter polymerization times, simpler reaction conditions, straightforward purification, extended duty cycle in simulated electrochromic devices, and enhanced colors, among many others. More importantly, the on-substrate prepared polyazomethines were consistently immobilized on the device electrodes without delamination with extended oxidation/neutralization switching cycles between the neutral and oxidized states.

Copper-based coordination polymers from thiophene and furan dicarboxylates with high isosteric heats of hydrogen adsorption

Co-reporter:Jie Yang, Martin Lutz, Anna Grzech, Fokko M. Mulder and Theo J. Dingemans

CrystEngComm 2014 vol. 16(Issue 23) pp:5121-5127

Publication Date(Web):27 Mar 2014

DOI:10.1039/C4CE00145A

Self-assembled Cu-based coordination polymers derived from thiophene-2,5-dicarboxylic acid (Cu-TDC) and furan-2,5-dicarboxylic acid (Cu-FDC) were synthesized via a solvothermal method and their H2 adsorption behaviour was investigated and contrasted with isophthalic acid (Cu-m-BDC) and terephthalic acid (Cu-BDC) derivatives. Both heterocyclic-based coordination polymers exhibit low surface areas (<300 m2 g−1) upon activation but unusually high isosteric heats of hydrogen adsorption (7.5–9.2 kJ mol−1). Hydrogen uptake values of 0.64–0.75 wt% (77 K and 1 bar) were recorded and these high uptake values are attributed to the optimal pore size (5.4–8 Å) and the polarizability of the 5-membered heterocycles.

SWCNT induced crystallization in amorphous and semi-crystalline poly(etherimide)s: Morphology and thermo-mechanical properties

Co-reporter:Maruti Hegde, Ugo Lafont, Ben Norder, Edward T. Samulski, Michael Rubinstein, Theo J. Dingemans

Polymer 2014 Volume 55(Issue 16) pp:3746-3757

Publication Date(Web):5 August 2014

DOI:10.1016/j.polymer.2014.06.017

In this study we contrast the behavior of an amorphous polyetherimide (ODPA-P3) with that of a semi-crystalline one (BPDA-P3) on introducing single-wall carbon nanotubes (SWCNTs; 0.1–4.4 vol.%). The SWCNTs act as a nucleating agent and induce crystallinity (up to 45%) in amorphous ODPA-P3; in BPDA-P3, the SWCNTs lower the onset of crystallization during thermal imidization, but decrease the overall degree of crystallinity. Tensile tests show that the yield strength is the same for both polyimides up to 0.3% SWCNT loadings. Above this concentration the yield strength for the BPDA-P3 nanocomposites remains constant whereas in the ODPA-P3 nanocomposites it increases from 80 to 126 MPa (1.2 vol.%). In the amorphous PEI, SWCNTs enhance the thermo-mechanical properties (Tg, storage- and elastic modulus, and yield strength), but in the semi-crystalline PEI there are little or no effects on the mechanical performance.

Conjugated poly(azomethine)s via simple one-step polycondensation chemistry: synthesis, thermal and optoelectronic properties

Co-reporter:Michiel L. Petrus, Ricardo K. M. Bouwer, Ugo Lafont, D. H. K. Murthy, René J. P. Kist, Marcus L. Böhm, Yoann Olivier, Tom J. Savenije, Laurens D. A. Siebbeles, Neil C. Greenham and Theo J. Dingemans

Polymer Chemistry 2013 vol. 4(Issue 15) pp:4182-4191

Publication Date(Web):13 May 2013

DOI:10.1039/C3PY00433C

Three conjugated triphenylamine-based poly(azomethine)s were prepared via well-known polycondensation chemistry using cheap and readily available starting materials and the results were contrasted with rrP3HT. Three functionalized diaminetriphenylamines (TPA(X), X = –H, –OMe, –CN) were polymerized in a simple one-step process with 2,3-dihydrothieno[3,4-b][1,4]dioxine-5,7-dicarbaldehyde (ThOx), with water being the only side product. The resulting polymers (TPA(X)ThOx, X = –H, –OMe, –CN) were characterized by GPC, IR and NMR, and show a good thermal stability. The opto-electronic properties could be tuned by changing the functionalization (X = –H, –OMe, –CN) on the triphenylamine moiety. Photovoltaic devices based on TPA(X)ThOx/PCBM (1:2) showed power conversion efficiencies in the range of 0.02–0.04%. TRMC measurements showed that the presence of PCBM as an electron acceptor facilitates the formation of free mobile charges after excitation of the polymer. The low device efficiencies are attributed to a low hole-mobility of the polymer in combination with poor active layer morphology.

Methoxy-Modified MOF-5: A MOF-5 Framework Prepared by a Mixed Ligand Approach

Co-reporter:Jie Yang;Anna Grzech;Fokko M. Mulder

European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 13) pp:2336-2341

Publication Date(Web):

DOI:10.1002/ejic.201201312

Abstract

In this paper, a series of MOF-5 frameworks based on a mixed diacid composition, i.e. 2-methoxyterephthalic acid and terephthalic acid, was synthesized by using a mixed-ligand approach. The MOF-5 structure remains intact when the 2-methoxyterephthalate concentration is in the range of 0–75 mol-%. By using this approach, the H₂ uptake capacity of MOF-5, at 77 K and 1 bar, can be improved by 10 % at a 2-methoxyterephthalate concentration of 75 mol-% (1.45 wt.-% vs. 1.32 wt.-% for MOF-5). This improvement is due to an enhanced isosteric heat of H₂ adsorption on a statistically determined number of sites.

The hydrogen storage capacity of mono-substituted MOF-5 derivatives: An experimental and computational approach

Co-reporter:Jie Yang, Anna Grzech, Fokko M. Mulder, Theo J. Dingemans

Microporous and Mesoporous Materials 2013 Volume 171() pp:65-71

Publication Date(Web):1 May 2013

DOI:10.1016/j.micromeso.2012.12.035

Herein we report the synthesis and hydrogen storage capability of four simple MOF-5 modifications, i.e. CH3-MOF-5, OCH3-MOF-5, Br-MOF-5 and Cl-MOF-5. The mono-substituted MOF-5s, with the exception of OCH3-MOF-5, exhibit the same topology as that of unsubstituted MOF-5. The BET surface areas are in the range of 680–2750 m2 g−1 for this series. Introducing these functional groups appears to have a significant effect on the thermal stability of the resulting frameworks. The thermal stability of CH3-MOF-5 is comparable to that of MOF-5 after heat-treatment, i.e. vacuum dried at 200 °C for 40 h, whereas the structure of Cl-MOF-5 collapses under the same conditions. Activated MOF-5, CH3-MOF-5, Br-MOF-5 and Cl-MOF-5 show 1.44 wt.%, 1.47 wt.%, 1.08 wt.% and 0.99 wt.% of hydrogen uptake capacities at 77 K and 1 bar, respectively. Experimental and computational results reveal that the introduction of –CH3, –Br and –Cl has only a minor effect on the isosteric heat of hydrogen adsorption for MOF-5 and the experimental values are in the range of 2.8 – 3.0 kJ mol−1 for all derivatives. This explains the similar hydrogen adsorption capacities of MOF-5 and CH3-MOF-5. The poor porous structures of Br-MOF-5 and Cl-MOF-5, however, result in lower hydrogen adsorption capacities compared to MOF-5 despite their similar isosteric heat of hydrogen adsorption. At high pressures (>20 bar), the excess hydrogen capacity appears to be a strong function of the specific surface area.Graphical abstractHighlights► The thermal stability of MOF-5 is affected by introducing –CH3, –OCH3, –Br or –Cl. ► The structural characteristics of the modified MOF-5s alter. ► The modified MOF-5s can be successfully activated via a thermal post treatment. ► –CH3, –Br or –Cl has only a minor effect on the enthalpy of H2 adsorption for MOF-5. ► The excess H2 uptake of the modified MOF-5s is a function of specific surface area.

SWCNT Induced Crystallization in an Amorphous All-Aromatic Poly(ether imide)

Co-reporter:Maruti Hegde, Ugo Lafont, Ben Norder, Stephen J. Picken, Edward T. Samulski, Michael Rubinstein, and Theo Dingemans

Macromolecules 2013 Volume 46(Issue 4) pp:1492-1503

Publication Date(Web):February 5, 2013

DOI:10.1021/ma302456h

We have selected two amorphous all-aromatic poly(ether imide)s with similar chemical structures but with different backbone geometries as matrices for SWCNT-based nanocomposites. Up to 4.4 vol %, SWCNTs could be incorporated using an in situ polymerization method. Nanocomposites prepared from aBPDA-P3, a nonlinear matrix polymer with a Tg of 230 °C, remains amorphous, and the presence of the SWCNTs reduces the Tg by 11 °C. No effect on E′ or stress–strain behavior was observed. When ODPA-P3 was used as the matrix, the SWCNTs appear to be highly compatible with this more linear polymer host. The SWCNTs act as a nucleating agent at concentrations as low as 0.1 vol %. XRD and TEM measurements show that the SWCNTs become embedded in a highly crystalline polymer matrix. The result is a significant change in thermomechanical properties. The polymer Tg was increased by 12 °C, from 196 to 208 °C, and due to the induced crystallinity, the modulus above Tg showed a dramatic increase. The neat polymer fails at Tg, but the 4.4 vol % nanocomposite shows a storage modulus of 1 GPa at 280 °C. Stress–strain measurements show a noticeable improvement in strain and toughness at low SWCNT loadings (0.1–0.3 wt %), which is indicative of good stress transfer between the SWCNTs and polymer matrix. At higher loadings the yield strength increases from 80 to 126 MPa at 4.5% strain. Our findings show that the poly(ether imide) backbone geometry determines whether the polymer is good host for SWCNTs. The more linear ODPA-P3 is able to maximize its interaction with the SWCNT surface. To the best of our knowledge, this is the first time that an amorphous polymer has been shown to develop a semicrystalline morphology in the presence of SWCNTs. Steric factors in aBPDA-P3 seem to inhibit favorable π–π interactions and prevent the polymer chains from adapting low-energy conformations that readily interact with the SWCNT surface.

Methyl modified MOF-5: a water stable hydrogen storage material

Co-reporter:Jie Yang, Anna Grzech, Fokko M. Mulder and Theo J. Dingemans

Chemical Communications 2011 vol. 47(Issue 18) pp:5244-5246

Publication Date(Web):30 Mar 2011

DOI:10.1039/C1CC11054C

Water stable methyl modified MOF-5s have been synthesized via a solvothermal route. Methyl- and 2,5-dimethyl-modified MOF-5s show the same topology and hydrogen uptake capability as that of MOF-5. The H2 uptake capacity of MOF-5, however, drops rapidly when exposed to the ambient air, whereas the H2 uptake capacities of the methyl modified MOF-5s remain stable for 4 days.

Sulfonated liquid crystalline polyesters as resin matrix for single wall carbon nanotube and nanodiamond composites

Co-reporter:D. Sordi;C. De Ruijter;S. Orlucci;S. J. Picken;E. J. R. Sudhölter;M. L. Terranova;L. C. P. M. de Smet;T.J. Dingemans

Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 5) pp:1079-1087

Publication Date(Web):

DOI:10.1002/pola.24519

Abstract

The focus of this study is on incorporating pendant sulfonate groups along the backbone of a liquid crystalline polyester (LCPE) with the aim to improve the dispersion of single wall carbon nanotubes (SWNTs) and nanodiamonds (NDs). Two LCPE matrices, one sulfonated (LCPE-S) and one nonsulfonated reference polymer (LCPE-R), were successfully synthesized via a melt condensation method using aromatic and aliphatic AB, AA, and BB-type monomers. Upon the introduction of SWNT and ND particles, the glass transition temperature (T_g) of the sulfonated LCPE increased from 21.5 °C to 41.0 °C and 41.9 °C, for SWNTs and NDs, respectively. When sulfonate groups were absent, a decrease in T_g was observed. The storage modulus (E′) followed a similar trend, i.e., E′ increased from 1.3 GPa to 5.2 GPa and 3.4 GPa, upon the addition of NDs and SWNTs. The LCPE-S showed a lower thermal stability due to the loss of sulfonate groups, i.e. the 5% weight loss temperature (T) is ∼280 °C for LCPE-S vs. 333 °C for LCPE-R. The decomposition temperature increased somewhat upon addition of the nanoparticles. The ability of dispersing carbon-based nanostructures combined with an accessible melt processing window makes sulfonated LCPs attractive matrices towards preparing nanocomposites with improved thermal and mechanical properties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.

All-aromatic liquid crystal triphenylamine-based poly(azomethine)s as hole transport materials for opto-electronic applications

Co-reporter:James C. Hindson, Burak Ulgut, Richard H. Friend, Neil C. Greenham, Ben Norder, Arek Kotlewski and Theo J. Dingemans

Journal of Materials Chemistry A 2010 vol. 20(Issue 5) pp:937-944

Publication Date(Web):11 Dec 2009

DOI:10.1039/B919159C

We have explored the opto-electronic properties of a new series of hole-transport materials based on main-chain triphenylamine-based poly(azomethine)s. 4,4′-Diaminotriphenylamine (TPA) was polymerized under benign conditions with either terephthalaldehyde (TPA-14Ta), 2,5-thiophenedicarboxaldehyde (TPA-25Th) or 1,3-isophthalaldehyde (TPA-13Iso) to yield polymers with an Mn of 5700–16000 g mol−1. Despite the non-linear, or ‘kinked’, backbone geometry, all polymers form lyotropic solutions in chloroform and this liquid crystal (nematic) ordering could be maintained in the solid film after spin casting. All polymers exhibit high glass-transition temperatures (Tg > 250 °C) and display outstanding thermal stabilities, i.e. 5% wt loss in excess of 400 °C under nitrogen. The HOMO and LUMO energy levels of these polymers were in the range of 5.0–5.3 and 2.4–3.3 eV below the vacuum level, respectively. Introduction of a thiophene heterocycle (TPA-25Th) resulted in a material with a low optical band-gap of approximately 2.0 eV, whereas TPA-14Ta and TPA-13Iso showed optical band gaps of 2.3 and 2.6 eV, respectively. A photovoltaic device based on a TPA-25Th/PCBM blend (1 : 3) showed an EQE of 20% at 500 nm. Under simulated sunlight, the device gives an open-circuit voltage of 0.41 V, a short-circuit current of 1.23 mA cm−2 and a fill factor of 0.24, leading to a power conversion efficiency of 0.12%.

High Tg nematic thermosets: Synthesis, characterization and thermo-mechanical properties

Co-reporter:Mazhar Iqbal, Theo J. Dingemans

European Polymer Journal 2010 Volume 46(Issue 11) pp:2174-2180

Publication Date(Web):November 2010

DOI:10.1016/j.eurpolymj.2010.08.010

In this paper the synthesis and characterization of a new family reactive nematic oligomers based on 4-hydroxybenzoic acid (4-HBA) will be presented. We modified the backbone using para- and meta-substituted aromatic monomers such as terephthalic acid (TA), isophthalic acid (IA), hydroquinone (HQ), resorcinol (RS), 4,4′-bisphenol (BP) and 3-hydroxybenzoic acid (3-HBA). All oligomers, with a target Mn of 5000 and 9000 g mol−1, were end-capped with reactive phenylethynyl functionalities and synthesized using standard melt condensation techniques. Curing of the phenylethynyl reactive functionalities proceeds through chain extension and crosslinking, depending upon the temperature and time and can be carried out between 310 and 400 °C. Fully cured nematic thermosets could be obtained with glass-transition temperatures previously not accessible (Tg > 400 °C). The cured polymers exhibit excellent tensile properties, i.e. tensile strength (83 MPa) and elongation at break (9%). This approach allows us to prepare all-aromatic polymers with a combination of useful properties such as ease of processing, high Tg’s, and excellent mechanical properties.

Liquid crystalline matrix polymers for aramid ballistic composites

Co-reporter:C. de Ruijter;S. van der Zwaag;R. Stolze;T.J. Dingemans

Polymer Composites 2010 Volume 31( Issue 4) pp:612-619

Publication Date(Web):

DOI:10.1002/pc.20835

Abstract

Five semi-flexible thermotropic liquid crystalline (LC) polyesters and poly(ester-amide)s were synthesized and used as matrix resins for Twaron™ aramid-based ballistic fabrics. The ballistic performance was investigated as a function of the neat resin content. For the most successful liquid crystalline polyester system, the effect of blending with styrene-ethylene-butylene-styrene (SEBS) and polyvinyl butyrate (PVB) rubber was also explored. The best neat resin V50 values were obtained for 20 wt% LC polyester (LCPE)-Twaron™ composites, that is, 418 m.s⁻¹, whereas SEBS/LCPE and PVB/LCPE modifications resulted in maximum V50 values of 460 and 466 m.s⁻¹, respectively. It was found that the ballistic impact resistance is strongly influenced by the elastic modulus of the resin component and to a lesser extent to the level of adhesion between the resin and fabric. The effect of resin content, resin strength, elongation-at-break, and resin toughness on the ballistic impact resistance was found to be small. The best ballistic protection could be obtained when the Young's modulus of the LC resin was in the range of 0.01–1 GPa. This result seems to be in agreement with existing inter-yarn friction models. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

The synthesis and characterisation of reactive poly(p-phenylene terephthalamide)s: A route towards compression stable aramid fibres

Co-reporter:Alwin Knijnenberg, Johan Bos, Theo J. Dingemans

Polymer 2010 Volume 51(Issue 9) pp:1887-1897

Publication Date(Web):20 April 2010

DOI:10.1016/j.polymer.2010.03.015

Herein we report on the synthesis of reactive poly(p-phenylene terephthalamide) (PPTA) oligomers and the preparation and characterisation of aramid fibres thereof. Methacrylate and maleimide reactive end-groups were found to be sufficiently stable in H2SO4 at 85 °C and they were used to prepare reactive PPTA oligomers. Lyotropic spin-dopes could be prepared with up to 20 wt% of reactive oligomer (Mn = 3900 g mol−1) and this modification did not interfere with the fibre spinning process and had no effect on the fibre tensile properties. The as-spun fibres did indeed show a modest (+0.1 GPa) improvement in compression strength. A high temperature treatment at 380 °C resulted in fibres which all show a significant increase in compressive strength over their as-spun precursors, i.e. from 0.7 to 0.9 GPa. When fibres were treated at 430 °C the compression values of the oligomer-modified fibres dropped somewhat, whereas unmodified PPTA displayed a compressive strength of 1.1 GPa. Other favourable fibre properties such as modulus and tenacity were not compromised.

All-aromatic liquid crystalline thermosets as high temperatures adhesives

Co-reporter:Mazhar Iqbal, Alwin Knijnenberg, Hans Poulis, Theo J. Dingemans

International Journal of Adhesion and Adhesives 2010 30(8) pp: 682-688

Publication Date(Web):

DOI:10.1016/j.ijadhadh.2010.06.006

All-aromatic liquid crystalline thermosets with high glass transition temperatures

Co-reporter:Mazhar Iqbal;Ben Norder;Eduardo Mendes

Journal of Polymer Science Part A: Polymer Chemistry 2009 Volume 47( Issue 5) pp:1368-1380

Publication Date(Web):

DOI:10.1002/pola.23245

Abstract

We have synthesized and characterized a new family of low melting all-aromatic ester-based liquid crystal oligomers end-capped with reactive phenylethynyl end groups. In a consecutive, high-temperature step, the reactive end groups were thermally activated and polymerization was initiated. This reactive oligomer approach allows us to synthesize liquid crystal thermosets with outstanding mechanical and thermal properties, which are superior to well-known high-performance polymers such as PPS and PEEK. We have modified an intractable LC formulation based on hydroquinone and terephthalic acid, with M_n = 1000, 5000, and 9000 g mol⁻¹, and varied the backbone composition using isophthalic acid, resorcinol, 4-hydroxy-benzoic acid, 6-hydroxy-2-naphthoic acid, and chlorohydroquinone. All fully cured polymers showed glass transition temperatures in the range of 164–275 °C, and high storage moduli at room temperature (∼ 5 GPa) and elevated temperature (∼ 2 GPa at 200 °C). All oligomers display nematic mesophases and in most cases, the nematic order is maintained after cure. Rheology experiments showed that the phenylethynyl end group undergoes predominantly chain extension below 340 °C and crosslinking above this temperature. Highly aligned fibers could be spun from the nematic melt, and we found that the order parameter 〈P₂〉 was not affected by the chain extension and crosslink chemistry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1368–1380, 2009

Poly(ether imide)s from Diamines with Para-, Meta-, and Ortho-Arylene Substitutions: Synthesis, Characterization, and Liquid Crystalline Properties

Co-reporter:Theo J. Dingemans, Eduardo Mendes, Jeffrey J. Hinkley, Erik S. Weiser and Terry L. StClair

Macromolecules 2008 Volume 41(Issue 7) pp:2474-2483

Publication Date(Web):March 15, 2008

DOI:10.1021/ma8000324

We have synthesized homologous series of para-, meta-, and ortho-substituted aryl ether diamine monomers, with either 2, 3, or 4 ether linkages per monomer unit, and prepared their corresponding poly(ether imide)s with 3,3′,4,4′-biphenyl dianhydride (BPDA) and 3,3′,4,4′-oxydiphthalic dianhydride (ODPA). All polymers were obtained in high molecular weights and gave good quality films with expected mechanical and thermal properties. The ortho- and meta-substituted diamines gave fully amorphous polymers, whereas the para-based diamines resulted in semicrystalline polymers. The glass-transition temperatures (Tg) drop in the order of para > ortho > meta, and the Tg drops considerably as a function of the aryl ether content and appears to level off at four ether linkages. The Tg values of our polymers were contrasted with a simple quantitative model and found to be in good agreement with the experimental results (±10 °C). BPDA in combination with an all para-substituted, aryl ether-based diamine (BPDA-P3) forms a thermotropic liquid crystalline phase. Optical microscopy experiments confirm the presence of a nematic melt. Highly aligned films could easily be obtained by stretching the films in the liquid crystal phase, and XRD analysis of quenched films confirmed the presence of a highly aligned smectic A phase (SmA) with an order parameter ⟨P2⟩ = 0.87, indicating a high degree of molecular alignment. To the best of our knowledge, this is the first example of an all-aromatic liquid crystalline poly(ether imide). Dynamic mechanical thermal analysis (DMTA) showed that the para-aryl ethers display broad β-transitions (25–160 °C), whereas the meta- and ortho-series do not show β-transitions. All PEIs with 3 or 4 aryl ether linkages become thermoplastic in nature. The purpose of this systematic study is to provided a basic set of design rules toward the design and synthesis of all-aromatic poly(ether imide) architectures.

Novel thermotropic esters-based polymers with broad nematic processing windows

Co-reporter:C. De Ruijter;J. Bos;H. Boerstoel;T. J. Dingemans

Journal of Polymer Science Part A: Polymer Chemistry 2008 Volume 46( Issue 19) pp:6565-6574

Publication Date(Web):

DOI:10.1002/pola.22967

Abstract

In this study, a new series of semiflexible liquid crystalline (LC) polyesters and poly(ester-amide)s were synthesized and characterized. Polymers based on 4-hydroxybenzoic acid (4-HBA), 6-hydroxy-2-naphthoic acid (HNA), suberic acid (SUA), and sebacic acid (SEA) were modified with hydroquinone (HQ) and different concentrations of 4-acetamidophenol (AP) to obtain a polyester and two poly(ester-amide)s, respectively. All polymers were successfully prepared using conventional melt-condensation techniques. The polymers were characterized by inherent viscosity measurements, SEC, hot-stage polarizing microscopy, DSC, and TGA. The mechanical behavior was investigated using DMTA and tensile testing. All linear polymers have T_gs in the range of 50–80 °C and melt between 120 and 150 °C. Our polymers display good thermooxidative stabilities (5% wt loss at ∼ 400 °C) and exhibit homogeneous nematic melt behavior over a wide temperature range (ΔN ∼ 250 °C). The liquid crystal phase was lost when high concentrations of nonlinear monomers such as 3-HBA (>27 mol %) and resorcinol (RC) (>23 mol %) were incorporated. The LC polyester based on 4-HBA/HNA/HQ/SUA/SEA could easily be processed into good quality films and fibers. The films display good mechanical properties (E′ ∼ 4 GPa) and high toughness, that is, ∼ 15% elongation at break, at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6565–6574, 2008

All-aromatic liquid crystal triphenylamine-based poly(azomethine)s as hole transport materials for opto-electronic applications

Co-reporter:James C. Hindson, Burak Ulgut, Richard H. Friend, Neil C. Greenham, Ben Norder, Arek Kotlewski and Theo J. Dingemans

Journal of Materials Chemistry A 2010 - vol. 20(Issue 5) pp:NaN944-944

Publication Date(Web):2009/12/11

DOI:10.1039/B919159C

Correlating on-substrate prepared electrochromes with their solution processed counterparts – towards validating polyazomethines as electrochromes in functioning devices

Co-reporter:Michael E. Mulholland, Daminda Navarathne, Michiel L. Petrus, Theo J. Dingemans and W. G. Skene

Journal of Materials Chemistry A 2014 - vol. 2(Issue 43) pp:NaN9108-9108

Publication Date(Web):2014/08/08

DOI:10.1039/C4TC01003E

Small-molecule azomethines: organic photovoltaics via Schiff base condensation chemistry

Co-reporter:M. L. Petrus, R. K. M. Bouwer, U. Lafont, S. Athanasopoulos, N. C. Greenham and T. J. Dingemans

Journal of Materials Chemistry A 2014 - vol. 2(Issue 25) pp:NaN9477-9477

Publication Date(Web):2014/05/08

DOI:10.1039/C4TA01629G

Correction: A low cost azomethine-based hole transporting material for perovskite photovoltaics

Co-reporter:M. L. Petrus, T. Bein, T. J. Dingemans and P. Docampo

Journal of Materials Chemistry A 2015 - vol. 3(Issue 32) pp:NaN16874-16874

Publication Date(Web):2015/07/28

DOI:10.1039/C5TA90163D

A low cost azomethine-based hole transporting material for perovskite photovoltaics

Co-reporter:M. L. Petrus, T. Bein, T. J. Dingemans and P. Docampo

Journal of Materials Chemistry A 2015 - vol. 3(Issue 23) pp:NaN12162-12162

Publication Date(Web):2015/05/11

DOI:10.1039/C5TA03046C

Methyl modified MOF-5: a water stable hydrogen storage material

Co-reporter:Jie Yang, Anna Grzech, Fokko M. Mulder and Theo J. Dingemans

Chemical Communications 2011 - vol. 47(Issue 18) pp:NaN5246-5246

Publication Date(Web):2011/03/30

DOI:10.1039/C1CC11054C

CAS:61088-96-8

2-Propenamide, N,N'-1,4-phenylenebis-

CAS:82994-21-6

Benzene, 1,1'-oxybis[3-methoxy-

Benzonitrile, 4-[bis(4-nitrophenyl)amino]-

CAS:97510-15-1

Benzonitrile, 4-[bis(4-nitrophenyl)amino]-

Benzenamine, 4,4'-[1,2-phenylenebis(oxy)]bis-

CAS:49860-97-1

Benzenamine, 4,4'-[1,2-phenylenebis(oxy)]bis-

Benzenamine, 4,4'-[oxybis(4,1-phenyleneoxy)]bis-

CAS:13080-88-1

Benzenamine, 4,4'-[oxybis(4,1-phenyleneoxy)]bis-

1H-Isoindole-1,3(2H)-dione, 2-[4-(acetyloxy)phenyl]-5-(phenylethynyl)-

CAS:404928-53-6

1H-Isoindole-1,3(2H)-dione, 2-[4-(acetyloxy)phenyl]-5-(phenylethynyl)-

Poly[(1,1',3,3'-tetrahydro-1,1',3,3'-tetraoxo[5,5'-bi-2H-isoindole]-2,2'-diyl
)-1,4-phenyleneoxy-1,4-phenyleneoxy-1,4-phenylene]

CAS:26615-46-3

Poly[(1,1',3,3'-tetrahydro-1,1',3,3'-tetraoxo[5,5'-bi-2H-isoindole]-2,2'-diyl )-1,4-phenyleneoxy-1,4-phenyleneoxy-1,4-phenylene]

Poly[iminocarbonyl-1,3-phenylenecarbonylimino(2,2'-disulfo[1,1'-biphen
yl]-4,4'-diyl)]

CAS:123375-25-7

Poly[iminocarbonyl-1,3-phenylenecarbonylimino(2,2'-disulfo[1,1'-biphen yl]-4,4'-diyl)]

Poly[(1,3-dihydro-1,3-dioxo-2H-isoindole-2,5-diyl)[2,2,2-trifluoro-1-(triflu
oromethyl)ethylidene](1,3-dihydro-1,3-dioxo-2H-isoindole-5,2-diyl)-1,4-
phenyleneoxy-1,4-phenyleneoxy-1,4-phenylene]

CAS:105009-93-6

Poly[(1,3-dihydro-1,3-dioxo-2H-isoindole-2,5-diyl)[2,2,2-trifluoro-1-(triflu oromethyl)ethylidene](1,3-dihydro-1,3-dioxo-2H-isoindole-5,2-diyl)-1,4- phenyleneoxy-1,4-phenyleneoxy-1,4-phenylene]

POLY[OXY-1,4-PHENYLENEOXY-1,4-PHENYLENEOXY-1,4-PHENYLENEIMINOCARBONYL(CARBOXYPHENYLENE)OXY(CARBOXYPHENYLENE)CARBONYLIMINO-1,4-PHENYLENE]

CAS:865446-16-8

POLY[OXY-1,4-PHENYLENEOXY-1,4-PHENYLENEOXY-1,4-PHENYLENEIMINOCARBONYL(CARBOXYPHENYLENE)OXY(CARBOXYPHENYLENE)CARBONYLIMINO-1,4-PHENYLENE]