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

Abstract

Polymeric allyl pyridinium salts were synthesized from styrene and 4-vinyl pyridine copolymers by quaternization and counteranion exchange reactions. The initiation capability of these copolymers, in conjunction with a photochemical free radical source such as benzoin, via an addition ± fragmentation mechanism in the cationic polymerization of cyclohexene oxide is investigated.

Initiation of Cationic Polymerization by Using Allyl Anilinium Salts in the Presence of Free Radical Initiators

“…Recently various types of allylonium salts have been synthesized and employed together with free radical sources in the cationic polymerization. [6][7][8][9][10][11][12][13][14][15][16] The mechanism of the initiation consistent with previous studies, is explained in terms of radical addition fragmentation. In this study, allylanilinium salts having different substituents on the allylic double bond are employed in the presence of various radical sources in the polymerization of CHO.…”

“…[6][7][8][9][10][11][12][13][14][15][16] The intermediate radical cation, formed by the addition of the thermally or photochemically generated radical on the allylic salt, undergoes fragmentation, producing another radical cation which is capable of initiating cationic polymerization as illustrated on the example of allyl thiophenium salts (Scheme 1).…”

“…Free radical addition fragmentation to specially designed allyl onium salts has been identified as an effective means of initiating cationic polymerization of cyclic ethers and vinyl ethers. − The intermediate radical cation, formed by the addition of the thermally or photochemically generated radical on the allylic salt, undergoes fragmentation, producing another radical cation which is capable of initiating cationic polymerization as illustrated on the example of allyl thiophenium salts (Scheme ).

1

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“…Compounds of these types include allylsulfonium salts, , allylpyridinium salts, , allyloxypyridinium salts, , allylphosphonium salts, etc. The attractive features of this technique include the flexibility of the polymerization conditions which can be tuned not only to the desired wavelengths but also to temperature ranges by choosing appropriate radical initiators.…”

Photocatalysis for the Formation of the C−C Bond

“…Another important class is that of polymerization reactions, which, however, will not be specifically addressed here, since the focus is on molecular synthesis. − A few reactions that involve the radical anions are known and involve coupling with radicals (see section 4.2.).…”