Preparation of polyelectrolyte‐coated pH‐sensitive poly(styrene) microcapsules and their application to initiation‐cessation control of an enzyme reaction

Abstract

Poly(styrene) microcapsules, prepared by depositing the polymer around emulsified aqueous droplets, were coated with a synthesized polyelectrolyte; i.e., copolymer of maleic acid (MA) with methyl vinyl ether (MVE), co-poly(MA, MVE), or with styrene (St), copoly(Ma, St). The permeability of the capsule membrane was investigated under various pHs of the outer medium using n-propyl alcohol as a permeant. It became apparent that either copoly(MA, St)- or copoly(MA, MVE)-coated microcapsules function as a pH-sensitive capsule. In particular, the former showed a dramatic change of the permeability in response to small differences in pH (5-6). By reference to the viscometric and electrophoretic studies of both copolymers, these were interpreted as being due to a pH-induced alteration of the configuration of the copolymer coating on the surface of the capsule membrane. When sucrose was hydrolyzed in an aqueous suspension of the copoly(MA, St)-coated capsules into which invertase was loaded, the hydrolytic reaction was initiated at pH 5. 5 and stopped at pH 4. 5. Such initiation-cessation control was repeated reversibly without damaging the capsules.