KINETICS AND MECHANISM OF THE CATIONIC POLYMERIZATION OF TETRAHYDROFURAN IN SOLUTION - THF-CH2CL2 AND THF-CH2CL2-CH3NO2 SYSTEMS

In the reported experiments, cationic polymerization of tetrahydrofuran (THF) in CH//2Cl//2 solvent and in mixed CH//2Cl//2/Ch//3NO//2 solvent was initiated with 1,3-dioxolan-2-ylium cations with AsF//6** minus and SbF//6** minus anions. Dissociation constants of the polytetrahydrofuranium ion pairs into ions were measured (e. g. , K//D equals 1. 5 multiplied by 10** minus **5M at 25 degree C and left bracket THF right bracket //0 equals 7. 0M; CH//2Cl//2 solvent) and were found to be more than 100 times lower than in CH//3NO//2 solvent at the same left bracket THF right bracket //0 and temperature. The rate constants k//p** plus and k//p** plus or minus , measured for degrees of dissociation ranging from 0. 03 to 0. 35 in CH//2Cl//2, were the same within an experimental error of measurements ( plus or minus 15% of the value of k//p). Dependence of k//p**I( equals k//p** plus equals k//p** plus or minus ) on the dielectric constant was a monotonous function in three different solvents, namely, CCl//4, CH//2Cl//2, and CH//3NO//2, which covered a large range of dielectric constants of the medium (from D equals 5 to D equals 22) and degrees of dissociation of the macroion pairs, alpha (from 0. 03 to more than 0. 70). Thus a decrease in the dielectric constant increases the rate constant k//p**I in the whole range of studied polarities of the medium.