Styrene-Maleic Anhydride and Styrene-Ma1eimide Based Copolymers as Building Blocks in Microencapsulation Procedures

Abstract

<p>This thesis addresses the formation and properties of capsule walls formed from new types of wall-former materials such as styrene-maleic anhydride and styrenemaleimide based preformed hydrophobic polymers. During the course of this study two new methods of encapsulation were developed: interfacial encapsulation based on the cross-linking reaction between oil-soluble styrene-maleic anhydride (SMA) copolymer and a water-soluble polyamine, or alternatively the hydrolysis reaction of tertbutyl styrene-maleic anhydride copolymers to produce non-cross-linked microcapsules, and photoinduced phase-separation encapsulation. The internal morphologies of the produced SMA microcapsules were found to depend primarily upon polymer/core-solvent interactions and rate of amine addition. Thus, the transition from matrix structures to hollow particles was observed with increasing volume fraction of hydrophobic non-solvent, dodecyl acetate, or alternatively by slowing the rate of polyamine addition. The effect of polymer loading, type of polymer and polyamine, and molecular weight of the preformed polymer on the observed morphologies was also investigated. The interfacial reaction between styrene-maleic anhydride type of copolymers and polyamines was shown to be fast in order of minutes. Hydrolysis, as the side reaction, was not found to play a significant role in the interfacial encapsulation reaction between SMA copolymers and amines. Styrene-maleimide based capsules were prepared by photo stimulated precipitation of azobenzene-functionalized copolymers dissolved in an oil phase and dispersed in a continuous phase. This microencapsulation process was found to be irreversible, and the resulting microcapsule walls were permanent even during storage in the dark, or irradiation with visible light.</p>