Functional pH-Responsive Polystyrene Microspheres Prepared by Surface Segregation of Diblock Copolymers

摘要

We report the preparation of functional polymer latexes by using amphophilic diblock copolymers as additives during the precipitation polymerization. The crosslinked microspheres with sizes ranging from 1 to 2 mum were prepared by precipitation copolymerization of styrene and divinylbenzene in solvent mixtures of acetonitrile and toluene. Because of the affinity between the polystyrene block and the monomers used for the polymerization, the amphiphilic diblock copolymer polystyrene-b-poly(acrylic acid) (PS-b-PAA) could be incorporated within the particle. The structure and the chemical composition of the particles were studied by means of SEM, FTIR spectroscopy, and X-ray photoelectron spectroscopy (XPS). Effective surface migration produced either hydrophilic or hydrophobic particles. Exposure of the particles to hot water provoked surface rearrangement and thus the acrylic acid functions to be revealed. On the contrary, the contact with either air or toluene induced migration of the polystyrene chains to the interface. Hence, the chemical composition at the surface can be reversibly modulated. Moreover, the PAA functionalized microspheres have the ability to reversibly change the external charge as a function of the pH by ionization and deionization of the acid functional groups.