An investigation of lead tetraacetate, <i>N</i>‐bromosuccinimide, <i>p</i>‐toluenesulfonyl azide, benzenediazonium fluoborate, and saccharine–dimethylaniline as chain initiators

Abstract

Abstract The thermal decomposition of several common materials in equimolar mixtures of styrene and methyl methacrylate has determined the initiator efficiency of the materials and permitted classification of the mechanisms as ionic or free radical. Both lead tetraacetate and p ‐toluenesulfonyl azide are such weak catalysts for homolytic polymerization that careful work is required to differentiate catalyzed and blank runs. The proposed catalyst system, saccharine–dimethylaniline, is also homolytic in nature but is even less efficient (1% conversion in 1 hr. at 60°). Benzenediazonium fluoborate is a good initiator but is carbonium ion in nature. The active species is not proved but may be the phenyl carbonium ion. N ‐Bromosuccinimide is an inhibitor not only for the monomer mixture but also for the homopolymerization of styrene. It is a catalyst however for the homopolymerization of methyl methacrylate. Apparently styryl free radicals are efficiently scavenged by N ‐bromosuccinimide or its fragments to terminate the radical chain. The principal products are probably the brominated materials.