Author

Lisa M. Croll

Date of Award

1-2004

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Supervisor

Harold D. H. Stöver

Abstract

Three different types of microcapsules are discussed in this thesis. The first, polyurea microcapsules serve as a basis for developing scanning transmission x-ray spectromicroscopy (STXM), an emerging technique for chemical analysis of nanoscale composites. Using STXM it was possible to visualise the location of two different polyurea species within a cross-section of polyurea microcapsule wall, approximately 200 nm thick.

The second type of microcapsules presented here are known as tectocapsules. There novel microcapsules were prepared by self-assembly of reactive poly(divinylbenzene-alt-maleic anhydride) microspheres and microgels at the oil-water interface and fixing them in place with poly(ethylenimines) (PEI). This resulted in the formation of highly permeable capsule walls consisting of interconnected microspheres that readily lost their core solvent upon drying. A mechanism for formation and rupture of tectocapsules is proposed.

The final type of microcapsules described here are called composite tectocapsules. These are capsules where colloids assembled at the oil-water interface are embedded in a polyurea matrix. These capsules were prepared with three types of colloids: poly(divinylbenzene-alt-maleic anhydride) microspheres and mircogels, porous poly(divinylbenzene) microspheres, and porous poly(divinylbenzene) microspheres functionalised with maleic acid. Composite capsules containing porous poly(divinylbenzene) microspheres functionalised with maleic acid showed altered release rates versus standard polyurea microcapsules. This change in release is attributed to solvent release through the microsphere's pores rather than the surrounding polyurea matrix. STXM was used to map the chemical compositions of these composite tectocapsules.


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