Epoxides photo-cross-linking

Although, in contrast to free radical polymerizations, cationic polymerizations are unaffected by O2, their importance is somewhat limited by the scarcity of appropriate macromolecules and suitable photoinitiators [3]. However, this does not apply to the photopolymerization of low molar mass epoxides (see Section 10.3). In this context, applications of photo-cross-linked epoxides in various fields such as stereolithography, volume holography, and surface coating are notable [16]. 

The Tsi/EtO-functionalized polysiloxanes were cross-linked in the presence of trifluoromethanesulfonic acid generated in an UV-initiated decomposition of PhalOSChCFs. The process is based on acid-catalyzed hydrolysis of =SiOEt groups and formation of =SiOH functions and their subsequent condensation. We have found that the use of Ph2l0S02CF3 gave much better results than Ph2lBF4, widely used in photo-initiated polymerization of epoxides [8]. 

TGA analyses were performed for polymer samples having different degrees of cross-linking. The decomposition of the linear oligomer starts at about 200 °C. Once cured and baked, the formed siloxane network is more thermally stable, and the decomposition begins at temperatures higher by 100-150 °C. The results are similar to those reported for analogous Tsi-modified siloxanes cross-linked by means of photo-initiated cationic polymerization of epoxides [8]. 

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