Synthesis of block copolymers by sequential carbenium ion polymerization

The sequential carbenium ion block copolymerization of ethyl vinyl ether (EVE) and isobutyl vinyl ether (IBVE) with N-vinylcarbazole (NVC) is described. Requisite conditions for the successful application of the sequential synthesis technique to these systems were established: (1) the use of stable carbocation initiator salts (e.g., Ph₃CSbCl₆) which lead to essentially terminationless polymerizations; (2) low solvent-to-monomer ratios in order to suppress any possible chain transfer to methylene dichloride molecules; (3) high ratios of initiator to monomer which create a pseudo-“living” system. The block products (PEVE-b-PNVC and PIBVE-b-PNVC) were isolated by precipitation and extraction. The intrinsic viscosities of these products displayed minima at 30°C.