THE EFFECT OF SOLVENTS ON THE RADIATION-INDUCED POLYMERIZATION OF ETHYL AND ISOPROPYL VINYL ETHERS

In the reported experiments, the radiation-induced cationic polymerization of ethyl and isopropyl vinyl ether was studied in a variety of solvents. The propagation rate constants were estimated and found to vary widely with the nature of the solvent. In particular, a good linear relationship existed between the logarithms of the rate constants and the reciprocal of the dielectric constants. The lowest rates were those of the highest dielectric constant solvents. These results have been interpreted in terms of the Laidler and Eyring theory of ion-molecule reactions. Isopropyl vinyl ether polymerizes much faster than ethyl vinyl ether, although the rates approach the same value at infinite dielectric constant. In contrast, ″free″ carbenium ion polymerizations initiated by stable carbenium ion salts in methylene chloride solution had similar values for both monomers. A comparison is made between the rate constants obtained with both methods of initiation.