DISPERSION POLYMERIZATION OF STYRENE IN POLAR-SOLVENTS .2. VISUALIZATION OF SURFACE-LAYERS OF STERIC STABILIZER ON DISPERSION-POLYMERIZED AND PRECIPITATED POLYSTYRENE LATEX-PARTICLES BY TRANSMISSION ELECTRON-MICROSCOPY

Steric stabilizers employed in the dispersion polymerization of styrene in polar solvents include hydroxypropyl cellulose, poly(N-vinylpyrrolidone) and poly(acrylic acid). These steric stabilizers were found, for the first time, in 10-20-nm layers on the polystyrene particle surfaces by direct observation of stained thin sections of the particles using transmission electron microscopy. When the polystyrene latexes were dissolved in dioxane and precipitated with methanol, new latex particles with a similar surface stabilizer morphology were obtained. These results support the grafting mechanism of stabilization during dispersion polymerization of styrene in polar solvents and suggest that the growing or precipitating particles are able to rearrange to maintain the grafted steric stabilizer on the particle surface at all times. © 1990.