A Structural Study on the Catalytic Activity in Ionic Polymerization

According to the theoretical conclusion reported previously on the activation energy of the catalytic polymerization, the experimental results relating to the monomer reactivity and the catalytic activity in anionic or cationic polymerization were interpreted. The catalytic activity in ionic polymerization can be quantitatively compared with the relative magnitude of the ionization potential or the electron affinity of monomer and components (A, D) of catalyst (AD). As a measure of the ionization potential or the electron affinity of monomer, the energy of the highest occupied (εho=α+λhoβ) or the lowest vacant (εlv=α−ηlvβ) π level of the monomer has been used, and as a measure of the electron affinity of component D, the pKa of the acid HD or the σ1 value. In anionic polymerization, it was found that the polymerization by the catalyst with the same component A took place only in the combination of the monomer and the catalyst in which the ηlv/pKa value was less than about 2.5×10−2, and that the catalytic activity, with the same component D, depends on the kind of solvent. The results in cationic polymerization were also discussed in connection with the electron affinity of component D or co-catalyst. And the monomer reactivity in ionic polymerization with the same catalyst was quantitatively discussed with the ηlv or λho value of monomer. From the accordance between the theoretical consideration and the experimental data, the present treatment was found to be useful for the purpose of the quantitative study of the catalytic activity and the monomer reactivity in ionic polymerization.