Polystyrene (1)/poly(butyl acrylate/amide type functional monomer) (2) two-stage emulsion polymers. Synthesis and thermomechanical properties of latex films

Polystyrene (PS) (1)/Poly (n-butyl acrylate (BA)/amide type functional monomer) (2) structured latex particles were prepared through emulsion polymerization varying the hydrophilicity of the functional monomer employed. The second-stage polymerization kinetics, the size and morphology of latex particles, and the location of the functional groups in the final latexes were studied, in order to relate them to the thermomechanical properties of films cast from these latexes. It has been shown that, as expected, increasing the hydrophobicity leads to a better homogeneity in the copolymer formed during the second-stage polymerization, while the more hydrophilic functional monomer partly homopolymerizes in a separate phase. However, the functionalization by all the monomers used in this work, prevents the PS seed particles to form a continuous skeleton (percolated network). Further heat treatments at 140°C do not lead to the formation of a continuous PS phase as for pure BA/pure PS two-stage particles. In addition, some thermally induced crosslinking effects are discussed in relation with the functional monomer location within the particles. © 1995 John Wiley & Sons, Inc.