1977 Volume 34 Issue 11 Pages 757-762
Formation of small holes in the membrane of polystyrene microcapsules (capsules) prepared by evaporating the organic solvent from the organic phase in (W/O) /W complex emulsions has been investigated by microscopic observation. The number of holes (1-10 μm in diameter) in the surface of the capsules apparently increased as the agitation rate of primary W/O emulsions increased from 500 rpm to 9000 rpm and the increase was remarkable for large capsules (300-400 μm in diameter). The release of encapsulated α-amylase from the capsules was also enhanced as the stirring rate of the primary emulsions increased. A number of fine bubbles were observed by optical microscopy in the capsule membranes and they were assumed to be formed from fine droplets (several micrometer diameter) produced in the primary emulsions by rapid stirring. The size and distribution of the bubbles in the membranes were similar to those of the holes in the surface of the capsules. Therefore, the holes in the capsule membranes were presumably formed at thin film parts which were around the droplets and were easily breaked by a slight change in experimental condition such as temperature in the microencapsulation process.
