Surfactant-free, cationic latices of poly(BMA-co-MMA) using AIBA initiator.

When polymer particles come into use, especially, for photonic crystal applications, their diameter, dispersivity, and refractive indices become very important. Poly(benzyl methacrylate) is known to be a kind of high refracive materials (n = 1.57) compared to poly(methyl methacrylate) (n = 1.49). Not many work was concerned for surfactant-free emulsion polymerization of benzyl methacrylate or its copolymerization using cationic initiators. Narrowly dispersed cationic poly(BMA-co-MMA) and PBMA latices were synthesized successfully by surfactant-free emulsion polymerization with AIBA. The influences of BMA/MMA ratio, BMA/MMA monomer and initiator concentrations, addition of DVB/EGDMA crosslink agent, and polymerization temperature on the kinetics and on the particle size and molecular weight were studied. Monodisperse cationic charged PBMA and poly(BMA-coMMA) latices with particle diameters varying between 160-494 nm and polymer molecular weights of the order 1.25 x 10(4) to 7.55 x 10(4) g/mol were prepared. The rate of polymerization increased with increasing MMA concentration in BMA/MMA ratio, AIBA concentration, DVB crosslink agent, and polymerization temperature. The particle diameter increased with BMA concentration in BMA/MMA ratio, AIBA concentration, and BMA/MMA monomer concentration. The molecular weight increased with BMA concentration in BMA/MMA ratio and BMA/MMA monomer concentration. The glass transition temperature of the latex copolymers decreased with increasing amount of BMA from 375 K for PMMA to 321 K for PBMA. It was, thus, found that the particle diameter and rate of polymerization as well as the polymer molecular weight for surfactant-free emulsion polymerization of BMA and MMA can be controlled easily by controlling the BMA/MMA ratio, BMA/MMA monomer concentration, AIBA concentration, and polymerization temperature.