Thermally induced radical promoted cationic polymerization using a novel N‐allyloxypyridinium salt

Abstract

A system consisting of a novel N-allyloxypyridinium salt and a radical initiator is highly appropriate for the thermal initiation of cationic polymerizations. Radicals formed upon the thermolysis (at 70 "C) of initiators as 2,2'-azoisobutyronitrile or benzoyl peroxide add to the double bond of the pyridinium salt N-[2-(ethoxcarbonyl)allyloxy]-~-picolinium hexafluoroantimonate (1). Subsequently, the pyridinium salt is fragmented yielding pyridinium-type radical cations, species able to initiate cationic polymerizations. In the case of the radical initiator phenylazotriphenylmethane (triphenylmethaneazobenzene), the polymerization is extremely rapid, since additionally the triphenylmethyl cation formed by electron transfer initiates the polymerization. The initiation capability of the system described was demonstrated for a number of monomers, such as cyclohexene oxide, butyl vinyl ether and the bifunctional 3,4-epoxycyclohexylmethyl 3',4'-cyclohexanecarboxylate. With the latter, an insoluble polymer network was readily obtained.

Photoinitiated Polymerization: Advances, Challenges, and Opportunities

“…Suitable radical sources for all modes of stimulation are available. 129,146,148,[160][161][162][163][164][165][166][167][168][169][170][171] Recently, acylgermanes originally developed as visible light photoinitiators for free radical polymerization 90,172 were also shown to activate cationic polymerization. 173,174 As in the case of all free radical promoted cationic polymerizations, the photochemically formed electron donating radicals (germyl radicals) are readily oxidized to germanium ions capable of initiating cationic polymerization (Scheme 15).…”

PolymericN-allyl vinylpyridinium salts as addition-fragmentation type initiators for cationic polymerization

“…Specially designed allylic salts such as thiophenium,8, 9 pyridinium,10 alkoxy pyridinium11–15 and phosphonium16 salts of the following structure, have been shown to participate in addition–fragmentation initiation. Such initiation occurs under free radical conditions whenever photochemically‐ or thermally‐generated radicals add onto the allylic salts bearing both activated unsaturation and a weak bond.…”

Cationic photopolymerization with the aid of pyridinium-type salts

“…Apart from the sulfonium salt dealt with in that section, allyloxy pyridinium salts 5 + X -, 6 + X -, 7 + X -, and 8 + X -, as well as allyl pyridinium salt 9 + X -(Tab. 2) were studied [32][33][34][35] . These salts exhibit a behavior similar to that of 1 + PF 6 -, e. g., they initiate cationic polymerization of CHO upon irradiation at wavelenghts at which they are light-absorbing, i. e. at k inc a 300 nm.…”