Study of stereoregularity of poly(vinyl ketone)s by proton nuclear magnetic resonance

Abstract

Abstract Two poly(vinyl ketone)s, poly(methyl vinyl ketone) (PMVK) and poly(phenyl vinyl ketone) (PPVK), are isotacticly synthesized. The 1 H‐NMR spectra of these polymers and of the meso and racemic model dimers help to determine the percentage of isotactic dyads using the area of the peaks of the non equivalent protons (H A and H B ) of the β‐methylene group of the chain. The difference between the chemical shifts of the H B and H B protons is exceptionally large (approximately 0,8 ppm for both isotactic PMVK and isotactic PPVK). The coupling constants and the β‐CH 2 and the α‐CH groups' frequencies are determined by applying the ABX 2 system. A spontaneous epimerization of isotactic PPVK is found; this is always accompanied by a degradation and leads to the assumption of a simultaneous photochemical reaction of the Norrish II type.