Microemulsion polymerization via hollow-fiber feeding of monomer

Microemulsion polymerizations of styrene (St), butyl methacrylate (BMA), an d methyl methacrylate (MMA) via hollow-fiber feeding of monomers have been studied for the preparation of nanosized microlatexes ranging from 15 to 65 nm. A water-soluble redox initiator was used for all polymerizations at ro om temperature. The monomer-starved latex particles were first generated in the initial microemulsion containing 0.5 wt % St or BMA or 2.0 wt % MMA st abilized by 1.5 wt % SDS or 1.0 wt % CTAB. The subsequent supply of monomer to the prepolymerized microemulsion proceeded via hollow-fiber feeding fro m the external monomer reservoir. The polymerization produced nearly unifor m (D-w/D-n < 1.15) latex particles having high molar masses (10(6) g/mol) a nd high polymer/surfactant weight ratios up to 15. The characteristic for t he St or BMA system is that the number of polymer particles per milliliter of latex (N-d) remained rather constant while latex particles grew to large r sizes (D-w) during the polymerization. But this is not the case for the M MA, system. The change of the number of polymer chains per latex particle ( n(p)) during the polymerization for all three monomers follows the same rel ationship between n(p) and D-w. The possible polymerization mechanisms for these monomers under the controlled feeding are discussed.