| Abstract: | The effect of polymerization conditions such as aging time of the catalyst, polymerization temperature, polymerization time, monomer concentration, and catalyst concentration on the polymerization of isobutyl vinyl ether was intensively studied by using the VCI3·LiCl–Al(i-Bu)3 system at an Al(i-Bu)/VCl3·LiCl ratio of 6 at which the cationic polymerization by VCl3·LiCl is sufficiently depressed. About 10 min aging of the catalyst in the presence of monomer yields a fairly stable catalytie system. The optimum polymerization temperature is around 30°C. The conversion increased with increasing monomer concentration, whereas the stereospecificity of polymerization decreased. Unexpectedly, the conversion decreased as total catalyst concentration increased. This phenomenon is explained by considering the deactivation of catalytic sites by the excess of Al(i-Bu)3. A reasonable mechanism from kinetic considerations is that two molecules of Al(i-Bu)3 deactivate the catalytic site in an equilibrium reaction. This deactivation is understandable by considering that the coordination of two molecules of Al(i-Bu)3 will occupy all the coordination positions of vanadium, so that there is no room for coordination of monomer coming to the catalytic site. |
