Photopolymerization of acrylonitrile and methyl methacrylate induced by triphenylamine

The photopolymerization of acrylonitrile and methyl methacrylate in the presence of triphenylamine (TPA) has been performed at 30°C in N,N-dimethylformamide and dimethylsulfoxide under irradiation with light of λ > 300 nm. TPA proved to be very effective for the polymerization of both monomers. An apparent activation energy of 4·3 kcal/mol was recorded for the photopolymerization of acrylonitrile. Equations of polymerization derived from a kinetic study were as follows: $\text{Rate of polymerization=K[TPA]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[Monomer]}{}^{\mathrm{1·0}}$$\text{Degree of polymerization=K′[TPA]}{}^{\mathrm{<mtext>-</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{[Monomer]}{}^{\mathrm{1·0}}$ From the UV spectrum of photoirradiated TPA in N,N-dimethylformamide solution, the formation of N,N-diphenylamine and aniline was observed, in which the photodecomposition of TPA might result.

Based on these results, it was suggested that radicals formed in the process of photodecomposition of TPA are responsible for the initiation of the photopolymerization, which proceeds through an ordinary mechanism of radical polymerization.