Facile synthesis of stereoregular carbon fiber precursor polymers by template assisted solid phase polymerization

Abstract

Predominantly isotactic stereoregular polyacrylonitrile copolymers (PAC) were prepared by solid phase polymerization techniques using hexagonal crystalline metal salts as template compounds. Stereoregular distributions of the prepared polymer were studied using high resolution 13C nuclear magnetic resonance spectroscopy (13C NMR) spectra. The extent of isotacticity was directly determined from the peak intensity of the methine carbon (CH). The triad tacticity from the intensities of methine carbon peaks were examined by statistical methods. It was found that the PAC was predominantly isotactic in stereoregularity, and its sequence distribution obeys Bernoulli statistics. The optimum polymerization conditions ensuring isotactic content over 50% were disclosed experimentally. The chemical composition of PAC was confirmed with 1H NMR data. The obtained polyacrylonitrile copolymers were also characterized for molecular parameters such as viscosity average molecular weight (Mv), number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index.