The effect of various catalysts on the monomer reactivity ratios in oxidative copolymerization of styrene and α‐methylstyrene.

Abstract

Oxidative copolymerizations of styrene (St) with α-methylstyrene (AMS) have been studied under 100 psi (690 kPa) oxygen pressure at 50 °C in the presence of various catalysts, namely 2,2′-azobisisobutyronitrile, cobalt(II) phthalocyanine pyridine complex and cobalt(II) tetraphenylporphyrin pyridine complex. The rates of copolymerization reactions (Rp) are obtained from oxygen consumption versus time plots. The reactivity ratios are computed with the Fineman–Ross and Kelen–Tüdös methods, using copolyperoxide compositions obtained from 1H NMR analysis. The effects of these catalysts on Rp, molecular weight and monomer reactivity ratios have been examined. Using all three catalysts, the comonomer incorporation in the copolyperoxide chain is controllable over a wide range by adjusting the comonomer feed ratios. The reactivity ratio results indicate that incorporation of St or AMS in the copolyperoxides is independent of initiating system. © 2014 Society of Chemical Industry