Spontaneous Terpolymeritation of 1,3-Cycloalkadiene, Styrene, and Acrylonitrile in the Presence of Zinc Chloride

Abstract

1,3-Cycloalkadienes of six- to eight-membered rings, such as 1,3-cyclohexadiene (1,3-CHD), 1,3-cycloheptadiene (1,3-CH_pD), and 1,3-cyclooctadiene (1,3-COD), underwent spontaneous terpolymerization with styrene (St) and acrylonitrile (AN) in the presence of ZnClz, which was accompanied by cycloaddition of the diene with AN when 1,3-CHD or 1,3-CH_pD was used as the diene. In the system involving 1,3-CHD as diene, the increase in ZnClz concentration increased both the rates of the two reactions and the terpolymer viscosity, while it scarcely affected the terpolymer composition. The terpolymers yielded in the terpolymerizations of 1,3-cycloalkadiene, St, and AN in the presence of ZnClz were composed of ∼50 mol% AN units and of ∼50 mol% donor monomer units, 1,3-cycloalkadiene and St. The terpolymerization was regarded as a binary copolymerization between charge-transfer (CT) complexes of 1,3-cycloalkadiene and St with AN coordinated to ZnC1₂, (AN)_c, and the resulting monomer reactivity ratio for the 1,3-cycloalkadiene-(AN)_c complex decreased in the order 1,3-CHD > 1,3-CH_pD > 1,3-COD. Such a variation in the monomer reactivity ratios with the diene is explained in terms of two interactions in the propagation: one between the diene and (AN)_c in the CT-complex and the other between the diene and a propagating radical having (AN)_c as a terminal unit.