Preparation of Hollow Polymer Microspheres——Effect of Acid Monomer Content

The core/shell latex microspheres of P(methyl methacrylate-buthyl acrylate-methyl acrylic acid) / P(styrene-methyl acrylic acid) copolymer were synthesized by multi-step emulsion polymerizations combining with pre-emulsification process. The core/shell copolymer microspheres thus produced were treated with alkali and acid solutions so that the mono-dispersed hollow copolymer microspheres with the hollowness as high as 30% were obtained. The sizes and their distributions as well as morphologies of polymer microspheres at various emulsion polymerization steps were characterized by means of DLS, TEM and FESEM. The effect of acid monomer content on the properties of seed and core/shell polymer latexes and the morphology of hollow copolymer microspheres thereof were emphatically examined. The results show that the optimum content of acid monomer in the preparation of seed latex particles is about 30%~35%, and that the content of acid units in the core layer of core/shell copolymer particle is as high as 85%. In addition, the formation mechanism of present hollow copolymer microsphere during the alkali/acid treatment was discussed.