Poly(alkyl α‐bromoacrylate)s. III. Tacticity analysis from 19 mHz 13C‐NMR spectroscopy

Abstract

AbstractPolymer tacticity was determined by 19 mHz 13C‐NMR spectroscopy for isotactic, atactic, and syndiotactic samples of six poly(alkyl α‐bromoacrylate)s. Included in this series were the methyl, ethyl, n‐propyl, i‐propyl, n‐butyl, and n‐pentyl esters. Complete assignments for the 10 pentad peaks of the carbonyl carbon resonance were achieved for all but the i‐propyl ester while a complete analysis of tetrad tacticity from the backbone methylene carbon resonance was possible for all but the methyl ester. The tetrad values calculated from the experimentally determined pentad contents were found to agree with the experimental tetrad values. As a result of insufficient peak separation of the quaternary carbon resonance, complete pentad assignments were possible in only a few instances. The polymerization reaction mechanisms were discussed in terms of the propagation statistics calculated from the experimentally determined tetrads and pentads. Both the atactic and syndiotactic polymers that were synthesized by free radical techniques displayed Bernoullian or random statistics while the stereochemical statistics of the isotactic polymers synthesized by a modified Grignard complex were more consistent with nonrandom or first‐order Markovian statistics.