Ring-opening polymerization of the cyclobutane adduct of tetracyanoethylene and ethyl vinyl ether by the initiating system vinyl ether-acetic acid adduct/zinc iodide. Synthesis of a molecular weight-controlled alternating copolymer of the two olefins

Abstract

Ring-opening polymerization of the cyclobutane adduct (1) of tetracyanoethylene (TCNE) and ethyl vinyl ether (EVE) was carried out with protonic acid/Lewis acid or EVE-acetic acid adduct (2)/ZnI2 as initiating systems in CH3NO2 at ambient temperature. Poly1s with narrow molecular weight distribution (MWD) were obtained with the systems acetic acid(AcOH)/ZnI2 or 2/ZnI2. In the polymerization with 2/ZnI2, the number-average molecular weight (M̄n) of the polymers decreases with increasing amount of 2/ZnI2, and increases in direct proportion to the monomer conversion. Furthermore, M̄n increases on addition of a fresh feed of monomer at the end of the first-stage polymerization. The MWD remains narrow throughout the reaction. On the basis of the reaction of 1 with an equimolar amount of 2 in the presence of ZnI2 and the diene 5 as a by-product formed by elimination of hydrogen cyanide from 1 in the polymerization, it was proposed that ZnI2 activates both the CH-OAc terminal groups of the growing polymer chain and monomer 1.