13C NMR Characterization of Copolymers Of 2-Chlorobutadiene-1,3 and 2,3-Dichlorobutadiene-1,3

Due to the facile free-radical polymerization of 2-chlorobutadiene-1,3 (chloroprene, CB), most experimental studies and commercial polymer preparations involve free-radical-initiated emulsion systems. From the reactivity ratios published in the literature and the calculated propagation rate of CB at 40°C, its rate is about 10 times faster than that of butadiene. Uniquely, among all the vinyl and diene monomers known, 2,3-dichlorobutadiene-1,3 (DCB) is more reactive than CB. Modification of the properties of polyCB through copolymerization is often relatively difficult. The comonomer most frequently used with CB is DCB, even though many other dienes and vinyl monomers have been tested. Copolymerization of DCB with CB modifies the polymer properties, as judged by evidence from increased crystallization resistance and the retention of building tack. The effect of DCB on the properties of the copolymer of CB and DCB is markedly influenced by the amount of comonomer present. Since no detailed studies have been reported on this monomer pair, we report here microstructure analyses by both 1H and 13C NMR on CB-DCB copolymers. However, it was the 18C NMR analyses which provided the major characterization of these copolymers, while the 1H NMR was only used for the analysis of their composition.