Liquid Crystalline Furandicarboxylic Acid-based Aaromatic Polyesters

The invention pertains to a fully aromatic liquid crystalline furandicarboxylic acid- based aromatic polyester obtainable from a mixture of monomers comprising 2,5- furandicarboxylic acid, p-hydroxybenzoic acid, an aromatic diol, and 5-40 mol% of an aromatic monocarboxylic acid selected from vanillic acid, ferulic acid, salicylic acid, and syringic acid, or mixtures thereof. In a preferred embodiment at least 90% of the 2,5-furandicarboxylic acid and aromatic monocarboxylic acid are bio-based monomers

Molecular Arrangement and Thermal Properties of Bisamide Organogelators in the Solid State

The crystal structure and phase behavior of bisamide gelators are investigated using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy, X-ray diffraction (XRD), and molecular modeling, aiming at a better understanding of bisamide gel systems. A homologous series of bisamide model compounds (nBAs) was prepared with the (CH2)nspacer between the two amide groups, where n varies from 5 to 10, and with two symmetric C17 alkyl tails. With increasing spacer length, the thermal properties show a clear odd-even effect, which was characterized using our newly developed analytical model DSCN(T). Using XRD, all studied nBA compounds turn out to have a layer-like structure. The XRD patterns of the odd BA series are very similar but show marked differences compared to the XRD patterns of the even series, which in turn are very similar. The odd-membered 5BA molecules are nearly perpendicular to the stacked layers, as described by a pseudo-orthorhombic unit cell, whereas the even-membered 6BA molecules are tilted at an angle with respect to the layer normal, as described by a triclinic unit cell. In both the odd and even series, the inter-layer interaction is the van der Waals interaction. The 6BA hydrogen bonding scheme is very similar to that of Nylon 6,10 α, unlike the 5BA H bonding scheme. The packing of the C17 alkyl tails in the 5BA layers is similar to polyethylene, and unlike 6BA. The slightly higher crystalline density of 6BA (1.038 g cm-3) as compared to 5BA (1.018 g cm-3) explains the higher melting point, higher enthalpy of fusion, and the observed shift of N-H stretch bands to higher wave numbers. The structural differences observed between the odd and even BA series reflect the different structure-directing effect of parallel versus antiparallel amide hydrogen bonding motifs. These differences underlie the observed odd-even effect in the thermal properties of nBA compounds.ChemE/Advanced Soft MatterRID/TS/Instrumenten groe

Conformational and Structural Changes with Increasing Methylene Segment Length in Aromatic-Aliphatic Polyamides

The synthesis and structural characterization of various aromatic–aliphatic polyamides are reported in this study. The polymers are obtained by solution polymerization of <i>p</i>-phenylenediamine with various aliphatic diacid chlorides. The resulting polyamides are labeled PA P-<i>X</i>, where <i>X</i> varies between 5 and 10 and corresponds to the number of carbon atoms of the dicarboxylic acid monomers used in the synthesis. The polyamides are obtained with <i>M</i>_n values of 10 kg/mol or higher, as determined by solution NMR spectroscopy and gel permeation chromatography (GPC). The polymers PA P-5 to PA P-8 degrade prior to melting, whereas only PA P-10 shows melting on heating. The structural changes in the polymers, with increasing methylene segments, are investigated by X-ray diffraction and molecular modeling. Conformational changes as a function of temperature have been studied by solid-state NMR spectroscopy. These studies have been illustrative in following the phase transformations in the aromatic–aliphatic polymers. For the crystal packing of the polymer based on the odd acid (PA P-5) a sheetlike structure, similar to that of the aromatic polyamide PPTA, is observed. Despite the presence of the odd spacer, PA P-5 exhibits a hydrogen bonding length very similar to that of PPTA, whereas the intersheet distance increases and the interchain distance decreases. As a result, the crystal structure of PA P-5 is distinctively different from that of the aliphatic polyamides having the same odd diacid, e.g. PA 65. In contrast, the crystal packing of PA P-6 with even diacid is similar to that of the α form of PA 46. The change of the chemical shift of the carbonyl groups with increasing number of methylene units suggests a weakening in the hydrogen bonding with respect to PPTA. For PA P-10 this weakening ultimately translates to melting of the polymer prior to degradation