CONTROLLED SYNTHESIS OF BICYCLIC 8-SHAPED POLY(CHLOROETHYL VINYL ETHER)S

The synthesis of bicyclic eight-shaped poly(chloroethyl vinyl ether)s of controlled molar masses and narrow polydispersities has been achieved in very good yield. The strategy used is derived from the one reported for the synthesis of monomacrocyclic poly(vinyl ether)s and polystyrene. The procedure consists in the preparation of a linear tetrafunctional precursor bearing two series of antagonist functions, namely, alpha,alpha'-distyrenyl-omega,omega'-diacetal-poly(CEVE). The synthesis and the characterization of this polymer by controlled living cationic polymerization of chloroethyl vinyl ether are first described. In a second step, performed in highly diluted conditions, the acetal ends of the precursor are selectively activated by an electrophilic catalyst in order to form carbocationic-like termini which rapidly add on the styrenyl function of the chain. The presence of two functions of each type on a poly(CEVE) chain allows the formation of two rings per chain. The structural investigation of the cyclized polymer by SEC and NMR supports that bicyclic eight-shaped poly(CEVE) can be prepared cleanly and almost quantitatively by this cyclization procedure based on unimolecular end-to-end coupling reactions.