Spontaneous copolymerization of 1,3‐cyclohexadiene with polar vinyl monomers

Abstract

AbstractIn the reactions of 1,3‐cyclohexadiene(1,3‐CHD) with polar vinyl monomers, CH2C(X)Y (X is ‐CN and CO2CH3; Y is CI, H, and CH3), the two α‐chlorosubstituted monomers underwent rapid spontaneous copolymerization, accompanied by the formation of a small amount of cycloadduct. Both polar monomers also gave predominantly copolymers in the reaction with 1,3‐cycloheptadiene(1,3‐CHpD) in lower yield. 1,3‐Cyclooctadiene (1,3‐COD) reacted only with α‐chloroacrylonitrile (CAN) to give a copolymer, while only cycloaddition took place in systems involving cyclopentadiene(CPD) as diene. The charge–transfer (CT) complex formation of 1,3‐CHD with CAN and methyl α‐chloroacrylate(MCA) was confirmed by ultraviolet spectroscopic studies and the equilibrium constants estimated were 0.18 and 0.07 liter/mole, respectively, at 25°C in chloroform as solvent. The activation energies for the copolymerizations of 1,3‐CHD with CAN and MCA in benzene were determined to be ca. 6.6 and 9.6 kcal/mole, respectively. In the system composed of 1,3‐CHD and CAN, only the copolymerization was affected by solvents used and oxygen. Although addition of ZnCl2 to the system resulted in the acceleration of the both reactions, the variation in the product ratio of copolymer to cycloadduct with ZnCl2 concentration showed a maximum. Based on the results in the present and preceding studies for systems involving 1,3‐cyclodienes and acceptor monomers, the relationship between the cycloaddition and the spontaneous copolymerization is discussed.