Novel method to prepare charged mosaic membrane by using dipole-like microspheres. I. Preparation and characterization of poly(4-vinylpyridine/n-butyl acrylate) seed latex with high solid content by soap-free emulsion polymerization

The stable latex of poly(4-vinylpyridine-co-n-butyl acrylate) (P4VP/nBA) wi th a solid content as high as 10 wt % was prepared by a modified soap-free emulsion polymerization. A mixture of water and organic solvents was employ ed as the continuous phase for increasing the solid content of the latex. S everal organic solvents were investigated and, among them, ethyl acetate (E A) and diethyl ether (DE) were effective. The stable latex with 10 wt % sol id content was prepared by charging 10 wt % EA or a EA/DE mixture (5 wt % e ach); however, more than 10 wt % solid content of the stable latex could no t be obtained even by charging more than 10 wt % EA or a EA/DE mixture. The stable latex with 10 wt % solid content, which was crosslinked with less t han 0.5 wt % (based on monomer) of ethylene glycol dimethacrylate, was prep ared by charging 10 wt % of EA. In this case, however, the pH of the contin uous phase had to be adjusted to lower than 4. The effects of EA on the cha racteristics of the resulting uncrosslinked latex were investigated by empl oying zeta-potential measurements and scanning electron microscopy. It was found that the mass of coagulum decreased as the EA increased. At 8 wt % of EA, a stable latex of 10 wt % solid content without any coagulum was obtai ned. The zeta potential of particles increased from - 100 up to 45.7 mV as the EA increased from 0 to 10 wt %. The effects of batch and semicontinuous copolymerization on the morphology of the microspheres were investigated b y using DSC and ultrathin cross-sectional transmission electron miscroscopy photos. A core-shell structure was not found, despite the batch copolymeri zation of 4VP(1)/nBA(2) (r(1) = 4.3, r(2) = 0.23), even with disparate reac tivity ratios. (C) 2000 John Wiley & Sons, Inc.