A kinetic study of the photoinitiated polymerization of isobutylene in the presence of vanadium tetrachloride

Abstract

AbstractA kinetic study of the polymerization of isobutylene with VCl4 induced with monochromatic light, wave length 436 nm, has revealed that the light‐induced polymerization is spontaneously quenched after the light source has been switched off; this process depends on the duration of preceding irradiation. The polymerization rate increases with increasing concentration of catalyst and monomer and with the intensity of light. The polymerization rate with respect to the catalyst and monomer concentration at constant light intensity can be expressed by an experimentally found relationship: The polymerization rate increase with decreasing temperature (in polychromatic visible light) and its activation energy for temperatures ranging from −20 to −78°C is E = −19,2±0,8 KJ/mol.The molecular weight of the polymer increases with increasing monomer concentration and with decreasing polymerization temperature. The “activation energy” of the degree of polymerization is EDP = −20,9±0,8 kJ/mol. The molecular weight of the polymer is independent of the catalyst concentration and of light intensity. It slightly decreases from the very beginning depending on conversion. The induction period decreases with increasing catalyst and monomer concentration at constant light intensity.The kinetic study has shown that the propagation in the polymerization of isobutylene proceeding via cation‐radical intermediates is cationic.