Effects of monomer composition on the swelling of core-shell copolymers with high content of carboxylic groups
The swelling properties of a series of core-shell copolymers, prepared by two-stage emulsion polymerization, based on different monomer compositions and with a carboxylic acid-rich core have been studied at room temperature. Swelling is highly dependent on pH, monomer composition, and the monomer type in the shell. Generally, the average particle size of the core-shell copolymers remains more or less the same within the pH range from 4 to 7. However, the particle size has increased significant in alkaline medium and reached a maximum at pH 10. Increasing the proportion of styrene to butyl acrylate or methyl methacrylate generally reduces the extent of swelling, presumably due to the lower hydrophilicity of styrene over butyl acrylate or methyl methacrylate.