PHOTOPOLYMERIZATION OF METHYL-METHACRYLATE USING A MORPHOLINE-SULFUR DIOXIDE CHARGE-TRANSFER COMPLEX AS THE PHOTOINITIATOR

Photopolymerization of the vinyl monomer (M) of methyl methacrylate (M MA) was kinetically studied by using near-UV/visible light at 40 degre es C and employing a morpholine (MOR) - sulfur dioxide (SO2) charge-tr ansfer ( C-T) complex as the photoinitiator. The rate of polymerizatio n (R-P) was found to be dependent on the morpholine: sulfur dioxide mo le ratio; the 1 : 2 (MOR-SO2) complex acted as the latent initiator co mplex C which underwent further complexation with the monomer molecule s to give the actual initiating complex I. Using the 1 : 2 (MOR-SO2) C -T complex as the latent initiator, the observed kinetics may be expre ssed as R-P proportional to [MOR-SO2](0.27)[M](1.10). Benzoquinone beh aved as a strong inhibitor. Polymers obtained tested positive for the incorporation of a sulphonate-type end group. Polymerization followed a radical mechanism. Kinetic nonideality as revealed by a low initiato r exponent and monomer exponent of greater than unity was explained on the basis of a prominent primary radical termination effect. (C) 1998 John Wiley & Sons, Inc.