1-(Bromoacetyl)pyrene, a novel photoinitiator for the copolymerization of styrene and methylmethacrylate

Abstract

The photopolymerization of styrene (Sty) with methylmethacrylate (MMA) induced by pyrene (Py), 1-acetylpyrene (APy) and 1-(bromoacetyl)pyrene (BrPy) has been investigated. Py was found to be completely ineffective while APy could just initiate the copolymerization in 15 h. Introduction of a Br in α-methyl group of APy significantly enhanced the polymerization efficiencies. The kinetics and mechanism of bulk copolymerization of Sty with MMA (Sty–co-MMA) using BrPy as a sole photoinitiator has been studied in detail. The kinetic data, inhibiting effect of benzoquinone and ESR studies suggest that the polymerization proceeds via a free radical mechanism. The system follows non-ideal kinetics ( R p α[BrPy] 0.7[Sty] 1[MMA] 1.04) and degradative solvent transfer reasonably explains these kinetic non-idealities. The co-monomer reactivity ratios calculated by using the Finemann–Ross and Kelen–Tudos models were r 1 (MMA)=0.48 and r 2 (Sty)=0.52. The value of k p 2 / k t for the present system is found to be 2.28×10 −5 l/mol/s. IR and NMR analysis confirms the random structure of the copolymer.