Mass transfer in miniemulsion polymerization

The use of very hydrophobic monomers in heterogeneous polymerisations is restricted because of insufficient mass transfer as a result of limited aqueous phase diffusion. Experimental evidence for a mass transfer mechanism in miniemulsion polymerisation that is based on the direct interaction between droplets as well as between droplets and particles (‘collisions’) rather than monomer diffusion is presented. Mass transfer that results in the formation of a copolymer in the miniemulsion polymerisation of a mixture of lauryl methacrylate and 4-tert-butyl styrene, is almost non-existing when physical contact between individual droplets is prevented by a membrane. However, monomer transport by diffusion is observed in reference experiments with more hydrophilic monomers.