Morphology of core-shell latex particles

The progressive dissolution of carboxylated latex particles with increasing pH was utilized to investigate the internal structure of core-shell latex particles, in comparison with that of copolymeric latex particles formed from the same monomers. The results indicated that in those latex particles which are formed when ethyl acrylate (EA) -methacrylic acid (MAA) or methyl acrylate (MA) -MAA mixture is polymerized in the presence of poly(MA-MAA) or poly(EA-MAA) seeds the shell is composed of the more hydrophilic poly(MA-MAA) molecules relatively high in MAA content and the core is composed of both poly(MA-MAA) and poly(EA-MAA) molecules, regardless of the order of the stage feed, while the copolymeric latex particles are relatively uniform from surface to center in distribution of all components except MAA. Examination of the distribution of the carboxylic groups in all of the latex particles showed their concentration to be highest at the surface and to decrease with proximity to the center in accordance with other findings reported in the literature.