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

Abstract

The synthesis and structural characterization of various aromatic–aliphatic polyamides are reported in this study. The polymers are obtained by solution polymerization of p-phenylenediamine with various aliphatic diacid chlorides. The resulting polyamides are labeled PA P-X, where X 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 Mn 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. Fo...