New initiation systems for cationic polymerisation

Abstract

Experimental results are presented to show that suitable free radical sources, in combination with aryldiazonium, diaryliodonium, and triarylsulphonium salts, may be used to promote cationic polymerisation of alkyl vinyl ethers and cyclic ethers and cyclic ethers such as tetrahydrofuran. Mechanistic features vary between the different classes as monomer but a general feature is a free radically initiated chain reaction leading to formation of initiating or propagating cationic centres. The process is especially weil suited to use of photochemically active free radical sources and, for polymerisation of tetrahydrofuran, it is shown that at least thirty propagating cations are produced for each photon of light absorbed byu the free radical initiator β,β-dimethoxy-β-phenylacetophenone. Product studies confirm that the initiating free radicals undergo electron transfer oxidation.