Cationic and pseudocationic polymerization of aromatic olefins—II The reactions following polymerization of styrene by perchloric acid

Abstract

We report spectroscopic and conductimetric studies on the reactions of styrene in the presence of perchloric acid (most in methylene dichloride but some in ethylene dichloride), both during and after the polymerization. During polymerization no ions are detectable, but at the end aralkyl (and subsequently allylic) ions are formed. Quantitative results show that ion formation sets in when the styrene concentration has fallen to four times the acid concentration; we interpret this finding as showing that the ester (oligo-)styryl perchlorate requires four molecules of styrene for stabilization in solution. The ionogenic reaction which follows polymerization changes its kinetics from second to first order. It is completely inhibited if the solution contains more water than acid, though this does not affect the polymerization itself. At the end of the polymerization, the ionogenic reaction sets up an equilibrium which involves many components and which is slowly shifted by formation of stable species; the position of equilibrium can be driven back towards predominance of non-ionic compounds by addition of fresh monomer. The relation between our work and that of other authors is discussed in detail.