High molecular weight monodisperse polystyrene microspheres prepared by dispersion polymerization, usine a novel bifunctional macromonomer

A novel bifunctional vinyl-terminated polyurethane macromonomer was applied to the dispersion polymerization of styrene in ethanol. Monodisperse polystyrene (PS) microspheres were successfully obtained above 15 wt % of macromonomer relative to styrene. The steep slope from the reduction of the average particle size reveals that the macromonomer can efficiently stabilize higher surface area of the particles when compared with a conventional stabilizer, poly(N-vinylpyrrolidone). The stable and monodisperse PS microspheres having the weight-average diameter of 1.2 mu m and a good uniformity of 1.01 were obtained with 20 wt % polyurethane macromonomer. The grafting ratio of the PS calculated from H-1 NMR spectra linearly increased up to 0.048 with 20 wt % of the macromonomer. In addition, the high molecular weights (501,300 g/mol) of PS with increased glass transition and enhanced thermal degradation temperature were obtained. Thus, these results suggest that the bifunctional vinyl-terminated polyurethane macromonomer acts as a reactive stabilizer, which gives polyurethane-grafted PS with a high molecular weight. (c) 2005 Wiley Periodicals, Inc.