A method for studying crosslinking in addition polymerization

Vinyl acetate has been copolymerized with small amounts of the diallyl ester of dithiodiglycolic acid (DADT). A method has been devised for the reduction of the disulfide crosslinks to sulfhydryl groups by means of thioglycolic acid under mild conditions, thereby enabling the recovery of the primary molecules of the original polymers. The method has been applied both to soluble copolymers (made with the lowest concentrations of DADT) and to insoluble space‐network copolymers (made with slightly higher concentrations of DADT). The polymers have been characterized before and after reduction by viscosity determinations. The reduction process had only a negligible effect on the viscosity of poly(vinyl acetate). The rate of reduction was diffusion controlled not only in the case of the gels, but apparently also in cases where soluble polymers were made with amounts of DADT less than necessary for gelation at high conversion. The DADT acted not only as a crosslinking agent, but also as a chain transfer agent. The method is suggested as potentially useful in developing the theory of three dimensional polymerization, and in studying the properties of space‐network polymers.