Alternative copolymerization of vinyl sulfides with maleic anhydride. III. Alternative copolymerization

Ethyl vinyl sulfide (EVS) and phenyl vinyl sulfide (PVS) were found to undergo alternative copolymerization with maleic anhydride (MAn) even in the absence of radical initiators. It is noted that both the rates and the reduced viscosities in these alternative copolymerization show a maximum at 50 mole-% comonomer mixture, anticipating that a 1 : 1 charge transfer complex is formed preceding polymerization. From spectroscopic studies, it was also observed that the formation of such a complex between vinyl sulfide and MAn was confirmed, but their equilibrium constants were quite small, i.e. 0.090 l./mole for PVS-MAn in CHCl₃ and 0.035 l./mole for EVS-MAn in CH₂Cl₂ at room temperature. The mechanism of these alternative copolymerizations is discussed.