Novel method of preparation of a charged mosaic membrane by using dipole-like microspheres. II. Preparation of dumbbell/egg-like microspheres

The dumbbell-like/egglike microspheres of poly(4-vinylpyridine/n-butyl acry late)/polystyrene [P(4VP/nBA)/PS] were prepared by soap-free seed emulsion polymerization. The effects of various polymerization parameters, such as t he amount of ethyl acetate (EA) in the continuous phase, swelling time, deg ree of crosslinking of seed polymer, polymerization temperature, and compat ibility of seed polymer and the secondary polymer, and so forth, on the for mation of dumbbell-like/egglike morphology were investigated by scanning el ectron microscopy (SEM) and transmission electron microscopy (TEM). It was found that secondary particles could be eliminated either by drastically in creasing the number of seed particles or by stripping EA from the seed late x by dialysis and evaporation under a vacuum, Swelling the seed particle wi th the secondary monomer was essential for the preparation of egglike micro spheres. For the localization of PS domains on one side of the egglike part icle, the most effective factors were to elevate the polymerization tempera ture up to 90 degreesC and simultaneously to lower the compatibility of the polymer on the seed particle surface with the phase of PS, while using the uncrosslinked seed latex. Crosslinking the seed latex was not suitable for localizing the PS domains in the seed particle, especially when the degree of crosslinking exceeded 0.5 wt % of EGDMA. (C) 2001 John Wiley & Sons, In c.