Novel Method of Preparation of a Charged Mosaic Membrane by Using Dipole-Like Microspheres. II. Preparation of Dumbbell/Egg-Like Microspheres

摘要

The dumbbell-likelegglike microspheres of poly(4-vinylpyridineln-butyl ac- rylate)/polystyrene [P(4VPBA)/PS] were prepared by soap-free seed emulsion poly- merization. The effe~ts of various polymerization parameters, such as the amount of ethyl acetate (EA) in the continuous phase, swelling time, degree of crosslinking of seed polymer, polymerization temperature, and compatibility of seed polymer and the sec- ondary polymer, and so forth, on the formation of dumbbell-like/egglike morphology were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that secondary particles could be eliminated either by drastically increasing the number of seed particles or by stripping EA from the seed latex by dialysis and evaporation under a vacuum. Swelling the seed particle with the secondary monomer was essential for the preparation of egglike microspheres. For the localization of PS domains on one side of theegglike particle, the most effective factors were to elevate the polymerization temperature up to 90°C and simultaneously to lower the compatibility of the polymer on the seed particle surface with tQe phase ofPS, 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 crosslink- ing exceeded 0.5 wt % of EGDMA.