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Abstract

A procedure is described for the polymerisation of cationically polymeriseable resins, using solid- state onium and organometallic salt photoinitiators bearing complex anions of group V elements.

The initiator is irradiated in the solid state by UV light and the gas(es) produced are allowed to diffuse into the resin film which is adjacent to but not in contact with the initiator, within a closed cell. Epoxide and vinyl ether monomers were successfully cured in this manner. The progress of polymerisation is followed by FTIR spectroscopy. The reaction is thought to be initiated via a Lewis Acid catalyst, but propagated via Brønsted species following interaction of the former with trace water in the film.

The effects of water on the polymerisation of epoxides were studied. Atmospheric moisture (humidity) was found to have a detrimental effect on the polymerisation while bulk water was tolerated at levels up to 5% w/w. These results are discussed in detail in the context of industry findings.

The presence of HF (hydrogen fluoride) in the gaseous photodecomposition products was determined by gas phase FTIR. and confirmed by ion chromatography. The rate of evolution of gaseous products upon irradiation of the initiator(s) is quantified in real time by dissolution in water and conductometric measurement using a fluoride ion specific electrode. A large proportion of the detected fluoride ion yield is attributed to the presence in the gaseous photo-products of XF5, the pentafluoride of the group V element. This is subsequently hydrolysed to yield multi-molar equivalents of fluoride ion per initiator molecule irradiated.

Hybrid systems are described which permit the selective and step-wise polymerisation of acrylate resins (by the conventional process) and epoxide resins by the above method.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry T Technology > TP Chemical technology
Departments:	School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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