MICROSTRUCTURAL ANALYSIS OF POLY(4-N-ACRYLAMIDE-2-HYDROXYBENZOIC ACID) AND POLY(5-N-ACRYLAMIDE-2-HYDROXYBENZOIC ACID) BY C-13 NMR-SPECTROSCOPY

The microstructural analysis of both poly(4-N-acrylamide-2-hydroxybenz oic acid) (poly(4-AHA)) and poly(5-N-acrylamide-2-hydroxybenzoic acid) (poly(S-AHA)) was carried out by one-dimensional C-13 n.m.r. spectros copy. The sensitivity of aromatic carbon signals to the stereosequence s was found to depend mainly upon the carbon ability to extend into th e maximum shielding zone of the neighbouring phenyl rings and carboxyl oxygens. The sensitivity of the amide carbonyl signal to the chain mi crostructure is influenced mainly by the gamma-gauche shielding effect . Solvent-induced effects in the spectra of poly-(4-AHA) are rationali zed in terms of H-bonds (for aromatic carbon signals) and bond conform ation changes (for amide carbonyl carbon signal). The increase of amid e carbonyl carbon signal sensitivity to the stereosequences in the spe ctrum of poly(S-AHA) in comparison with that of poly(4-AHA) reflects t he conformation changes, induced by the transfer to more sterically cr owded polyacrylate. For both poly(4-AHA) and poly(S-AHA) prepared by r adical polymerization the Bernoullian statistics is required to fit th e observed intensities at the triad and pentad level. (C) 1997 Elsevie r Science Ltd.