Controlled aggregation of polymer latices part 3. Influence of temperatureand surface chemistry

The possibility of obtaining narrowly dispersed particles through the contr olled aggregation of polymer latices has been investigated. Concentrated po lystyrene, poly(styrene-co-acrylic acid) and poly(styrene-co-butadiene-co-a crylic acid) latices were aggregated through the addition cationic surfacta nt under stirring. The method under investigation was proven to be effectiv e in obtaining 5-15 mum particles with a narrow size distribution and a str ong control of the average size. The aggregation properties of polymer lati ces were related to their chemical nature (chemical structure of the polyme r and surface chemistry); the trends observed were explained through calcul ations of the fundamental forces involved in this process. Important differ ences were found between the aggregation of the latices that contain acryli c acid as a comonomer and those without acrylic acid. Narrow size distribut ions, with geometric standard deviations between 1.2-1.35 were obtained onl y for the latices containing acrylic acid. It was shown that on the surface of these particles there is a hairy layer formed by the polyacrylic acid c hains. The thickness of this layer is dependent on the chemical environment and temperature. Its presence was demonstrated by capillary viscometry and electrophoretic mobility measurements.