Controlled cationic polymerization of cyclopentadiene with B(C6F5)3 as a coinitiator in the presence of water

The controlled cationic polymerization of cyclopentadiene (CPD) at 20 °C using 1‐(4‐methoxyphenyl)ethanol (1)/B(C₆F₅)₃ initiating system in the presence of fairly large amount of water is reported. The number–average molecular weights of the obtained polymers increased in direct proportion to monomer conversion in agreement with calculated values and were inversely proportional to initiator concentration, while the molecular weight distribution slightly broadened during the polymerization (M_w/M_n ～ 1.15–1.60). ¹H NMR analyses confirmed that the polymerization proceeds via reversible activation of the C? OH bond derived from the initiator to generate the growing cationic species, although some loss of hydroxyl functionality happened in the course of the polymerization. It was also shown that the enchainment in cationic polymerization of CPD was affected by the nature of the solvent(s): for instance, polymers with high regioselectivity ([1,4] up to 70%) were obtained in acetonitrile, whereas lower values (around 60%) were found in CH₂Cl₂/CH₃CN mixtures. Aqueous suspension polymerization of CPD using the same initiating system was successfully performed and allowed to synthesize primarily hydroxyl‐terminated oligomers (F_n = 0.8–0.9) with M_n ≤ 1000 g mol^?1 and broad MWD (M_w/M_n ～ 2.2). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4734–4747, 2008