Synthetic Applications of Cationic Ring-Opening Polymerization

SYNTHETIC APPLICATIONS OF CATIONIC RING-OPENING POLYMERIZATION 

There are two large-scale industrial processes based on the cationic ringopening polymerization production of polyacetals by polymerization of 

5-trioxane and production of poly(tetramethylene oxide)glycols (PTMEG) by polymerization of tetrahydrofuran. There are several other industrial processes using cationically polymerizable monomers described in previous sections, but for some systems (e.g., oxiranes, lactones, lactams, siloxanes), other mechanisms of polymerization (anionic or coordination mechanisms) are preferred. 

The term living polymerization has been used quite frequently to describe the systems approaching to various extent the criteria defined originally by Szwarc [97]. The problem of the applicability of this term has been addressed in a few papers [257-259]. 

In cationic ring-opening polymerization, there are not too many examples of the systems in which ratios of kplk, are known. In the polymerization of substituted aziridines and substituted thietanes the ratios of rate constants of chain transfer to polymer to the rate constants of propagation have been measured and at least the value obtained for polymerization of N-/-butylaziridine (1.2-104) [260], indeed indicates the living character 

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IV. SYNTHETIC APPLICATIONS OF CATIONIC RING-OPENING POLYMERIZATION... 

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