Metathesis polymerization of cyclopentene: microstructure of the polymer

Abstract Metathesis polymerizations of cyclopentene initiated with the WCl 6 /Sn(CH 3 ) 4 catalytic system were carried out in benzene under various conditions. The effects of polymerization parameters on the microstructure of the polymer were investigated. The initiation process was followed step by step through 1 H-NMR and u.v./vis spectrometry. Two main species having chemical shifts of 9.48 and 10.30 ppm are detected by 1 H-NMR. One of the species is believed to be the carbene complex, [W]=CH 2 , coordinated by olefin. u.v./vis analyses show a maximum absorbance around 485 nm for the postulated carbene complex and the spectrum was hardly modified upon addition of cyclopentene. It is concluded that the active centers in this system cannot be detected through spectroscopy. From analyses of the polymer microstructure, it is found that low reaction temperature, low monomer conversion and high monomer concentration lead to a high cis content and a high cis/trans blockness structure. The results are interpreted in terms of a mechanism where chain propagation occurs through two different types of active centers.