Control of particle morphology and film structures of carboxylated poly(methyl methacrylate)/poly (n-butylacrylate) composite latex Particles

Particles with a hard core of 66% poly(methyl methacrylate)/34% poly(n-butyl acrylate) copolymer and a soft shell of pure poly(n-butyl acrylate) were synthesized via a two-stage emulsion polymerization process. The particle morphology and the surface structure of the dispersion films were analyzed by atomic force microscopy (AFM). The results, concerning single particle structure and the corresponding films, are correlated to macroscopic properties similar to the minimum expected from the kinetic side. The different morphologies are compared to the findings reported in a previous article, where the corresponding soft-core/hard-shell dispersions were analyzed (Kirsch et al. Colloid Surf A 2001, 183-185, 725). The key parameters to tailor the particle morphology are thermodynamic factors, for example: (i) the stage ratio and (ii) the phase compatibility and kinetic factors affecting the polymer chain mobility (e.g., cross-linking and polymer glass transition temperature). In this work, we used a core material which is in the glassy state at room temperature, however, above the polymer glass temperature (T g ) at polymerization temperature. The diffusion of the second-stage polymer chains is therefore strongly affected. From this point of view, the major influence for the current system is expected from the kinetic side. The different morphologies of the single particles are discussed qualitatively and the effects of reaction parameters and our results from previous work are compared to the results of computer simulation work and other results.