Carbon‐13 nuclear magnetic resonance spectroscopy of polystyrene and poly‐α‐methylstyrene

Abstract

Abstract The carbon‐13 high resolution nuclear magnetic resonance spectra with proton spin decoupling of polystyrene and poly‐α‐methylstyrene were measured. The spectra clearly split corresponding to triad, tetrad, and partially pentad placements, and these peaks were tentatively assigned. By comparison of the triad tacticity of poly‐α‐methylstyrene determined from carbon‐13 spectra with that from proton spectra, it was confirmed that the nuclear OVERHAUSER effect due to proton decoupling has little effect on the relative intensities of the peaks assigned to chemically equivalent carbons except for stereochemical configuration. The stereospecific polymerization mechanisms are discussed on the basis of the microtacticity determined from carbon‐13 spectra. As a result, it is concluded that poly‐α‐methylstyrene polymerized with cationic and anionic catalysts can be described by BERNOULLIAN statistics, while the atactic polystyrene does not obey BERNOULLIAN but first or second order MARKOVIAN statistics.