Morphologies of polybutylacrylate/poly(styrene-co-methyl methacrylate) latex prepared by starved emulsion polymerization -: Part 1.: Thermodynamics equilibrium morphology

Heterogeneous latexes were prepared by a semicontinuous seeded emulsion polymerization process under monomer starved conditions at 80degreesC using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(butyl acrylate) latexes were used as seeds. The second-stage polymer was poly(styrene-co-methyl methacrylate). By varying the amounts of methyl methacrylate (MMA) in the second-stage copolymer, the polarity of the copolymer phase could be controlled. Phase separation towards the thermodynamic equilibrium morphology was accelerated either by ageing the composite latex at 80degreesC or by adding a chain-transfer agent during polymerization. The morphologies of the latex particles were examined by transmission electron microscopy (TEM). The morphology distributions of latex particles were described by a statistical method. It was found that the latex particles displayed different equilibrium morphologies depending on the composition of the second-stage copolymers. This series of equilibrium morphologies of [poly(butyl acrylate)/poly(styrene-co-methyl methacrylate)] (PBA/P(St-co-MMA)) system provides experimental verification for quantitative simulation. Under limiting conditions, the equilibrium morphologies of PBA/P(St-co-MMA) were predicted according to the minimum surface free energy change principle. The particle morphology observed by TEM was in good agreement with the predictions of the thermodynamic model. Therefore, the morphology theory for homopolymer/homopolymer composite systems was extended to homopolymer/copolymer systems. (C) 2002 Society of Chemical Industry.