Donor–acceptor interaction in cationic polymerization. VI. Influence on the molecular weight of polyisobutylene of some anions derived from the complexes of aluminum trichloride with some electron donors

The concentration dependence of the specific conductivity of complexes of aluminum trichloride with ethanol, diethyl ether, and phenetole in a molar ratio of 1 : 1 and in 2EtOH·AlCl3 and EtOH·2AlCl3 complexes has been measured. Conductivity measurements were carried out in ethyl chloride at −78.5°C. Molar conductivity and the degree of dissociation of the complexes studied are concentration-independent which proves an extensive association of ions. Polymerizations of isobutylene carried out in the presence of these complexes and under the same conditions as the conductivity measurements have shown that the molecular weight of polyisobutylene formed is inversely proportional to the concentration of the complex over the whole range of concentrations studied. It can be deduced from the relation between the specific conductivity and the molecular weight that only the ionized part of the complex asserts itself in the chain-breaking processes. The chain-breaking efficiencies of various anions are given and allow one to draw conclusions about the mode of ionization of donor molecules after the interaction with the acceptor, viz. aluminum trichloride.