Chain growth from cyclic oligomers

Tertiary amines like benzyldimethylamine, pyridine, and imidazole have been widely used as a base to initiate the anionic polymerization of PGE and its derivatives as well as for the synthesis of epoxy resins of diglycidyl ether of bisphenol A (DGEBA). Even if initiation occurs with amine alone, the introduction of an alcohol is a common procedure to suppress the observed induction period and increase the polymerization rate. Two initiation mechanisms have been proposed (Scheme 18) (1) direct nucleophilic attack of the amine onto the cyclic monomer to yield the zwitterion (a) and (2) formation of alkoxide (b) via proton transfer in the presence of alcohol. Fast exchange between dormant alcohol and active alkoxide allows chain growth from both initial amine (a) and alcohol (b). Poly(PGE) oligomers whose degree of polymerization does not exceed 5 are obtained. The presence of terminal double bonds indicates significant transfer to the monomer via... 

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