Copolymers of a-double bond-containing polyurethane (DPU) and styrene (ST) were prepared by concentrated emulsion copolymerization, using a cumyl bydroxy peroxide/tetraethylene pentamine (CHPO/TEPA) redox system as initiator, sodium dodecyl sulfate/cetyl alcohol (SDS/CA) as surfactant, and polyvinyl alcohol (PVA) as a liquid film reinforcer (LFI). DPU was first synthesized from the appropriate precursors, then diluted with ST and dissolved completely in ST. This solution was subsequently used as the dispersed phase of a concentrated emulsion in water. Finally, the DPU/ST (PUS) copolymers were obtained by the copolymerization of DPU and ST in the above concentrated emulsions with a volume fraction of the dispersed phase up to 80-90%. The effects of surfactants, initiators, and monomer volume fractions, on the stability of the concentrated emulsion copolymerization procedure and the average sizes of PUS copolymer latex particles, were evaluated. IR spectral results verified that PUS copolymers were obtained, and the DSC diagrams of DPU precursor and PUS copolymers with different weight ratios of DPU/ST were presented. (C) 2004 Wiley Periodicals, Inc.