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J. Kuriata, J. Chojnowski


Mechanism of the cationic polymerization of octamethyl-1,4-dioxatetrasilacyclohexane

Polimery 1995, No 7-8, 428


DOI: dx.doi.org/10.14314/polimery.1995.428

Summary

The polymerization of octamethyl-1,4-dioxatetrasilacyclohexane (2D2) is of interest as it leads to the simplest stable polysilaether, i.e. the fully methylated silicon analogue of polyoxyethylene. This polymer combines structural properties of two important organosilicon polymers: polydimethylsiloxane and polydimethylsililene. The kinetics of the cationic ring-opening polymerization 2D2 in methylene chloride initiated with strong protic acids was studied. The results pro vide evidence of the existence of intermediate tertiary siloxonium ions of cyclic structure situated at the end of the polymer chain. They form active propagation centres in this polymerization and are intermediates in the direct interconversion of the lower cyclic oligomers. This interconversion involves ring expansion — ring contraction isomerization of the siloxonium ion chain end [Scheme (4)].


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