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) with 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 employed as the continuous phase for increasing the solid content of the latex. Several organic solvents were investigated and, among them, ethyl acetate (EA) and diethyl ether (DE) were effective. The stable latex with 10 wt % solid content was prepared by charging 10 wt % EA or a EA/DE mixture (5 wt % each); however, more than 10 wt % solid content of the stable latex could not 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 than 0.5 wt % (based on monomer) of ethylene glycol dimethacrylate, was prepared by charging 10 wt % of EA. In this case, however, the pH of the continuous phase had to be adjusted to lower than 4. The effects of EA on the characteristics of the resulting uncrosslinked latex were investigated by employing z-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 obtained. The z potential of particles increased from 2100 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 by using DSC and ultrathin cross-sectional transmission electron miscroscopy photos. A core– shell structure was not found, despite the batch copolymerization of 4VP(1)/nBA(2) (r1 5 4.3, r2 5 0.23), even with disparate reactivity ratios. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1731–1740, 2000