Photopolymerization of methyl methacrylate using morpholine–bromine charge transfer complex as the photoinitiator

Abstract

Photopolymerization of methyl methacrylate (MMA) was kinetically studied using near UV/visible light at 40°C and by employing the morpholine (MOR)–bromine (Br2) charge transfer (CT) complex as the photoinitiator. The rate of polymerization (Rp) was dependent on the morpholine:bromine mole ratio; the 1:2 (MOR–Br2) CT complex acted as the latent initiator complex C which underwent further complexation with monomer molecules to give the actual initiator complex, I. Using a 1:2 (MOR–Br2) CT complex as the latent initiator, the initiator exponent for bulk photopolymerization of MMA was 0.08 and the monomer exponent determined from studies of photopolymerization in a carbon tetrachloride diluted system was 1.20. Benzoquinone behaved as a strong inhibitor and the polymers tested positive for the incorporation of bromine atoms as end groups. Polymerization followed a radical mechanism. Kinetic non-ideality was revealed by low (≪0.5) initiator exponent and a monomer exponent of greater than unity; it was explained in terms of primary radical termination.