Photopolymerization of Methyl Methacrylate with N-Benzylpyridinium Thiocyanate

Abstract

The photopolymerization of methyl methacrylate (MMA) with N-benzyl-pyridinium thiocyanate (BPT) was studied. The photopolymerization of MMA with BPT in dichloromethane gave an oligo(methyl methacrylate) (OMMA), which was presumably formed by initiation with thiocyano radical and termination with N-benzylpyridinyl radical. The photopolymerization was also accelerated by the addition of carbon tetrachloride, which captured effectively the pyridinyl radical as was also the case with N-benzylpyridinium bromide. Photopolymerization of MMA with N-benzylpyridinium chloride (BPC)–KSCN–CCl4 in an aqueous-organic two-phase was also examined. The results suggested the following BPC-recycling photo-initiation mechanism. BPT formed by the ion exchange reaction between BPC and KSCN in an aqueous layer photodecomposed to the SCN and N-benzylpyridinyl radical. The latter reacted with carbon tetrachloride to produce BPC and ·CCl3. Both ·SCN and ·CCl3 initiated the polymerization of MMA, and BPC was transferred to the aqueous layer. Photopolymerization in aqueous-organic two-phase was also remarkably accelerated in an emulsified system with sodium dodecyl sulfate or N-cetylpyridinium bromide, each of which increased the interface area between the aqueous and organic layers and facilitated the phase-transfer.