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

Abstract

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 (Mw/Mn ∼ 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 (Fn = 0.8–0.9) with Mn ≤ 1000 g mol−1 and broad MWD (Mw/Mn ∼ 2.2). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4734–4747, 2008

Kinetic study on the living/controlled cationic polymerization of p‐methoxystyrene coinitiated by tris(pentafluorophenyl)borane

“…From this plot also, the reaction order with respect to H 2 O was determined to be −2.08. A close value (−2.24) was similarly obtained while looking at the kinetics of cyclopentadiene polymerization in the presence of water ([H 2 O] > [B(C 6 F 5 ) 3 ]) with the same catalytic system 27. We assume that in the case of the polymerization of p ‐methoxystyrene with B(C 6 F 5 ) 3 , reaction order of −2 in H 2 O concentration is due to the renown ability of B(C 6 F 5 ) 3 to form with water exclusively complex B(C 6 F 5 ) 3 ·2H 2 O in acetonitrile solution 28…”

“…) with the same catalytic system. 27 We assume that in the case of the polymerization of p-methoxystyrene with B(C 6 F 5 ) 3 , reaction order of À2 in H 2 O concentration is due to the renown ability of B(C 6 F 5 ) 3 to form with water exclusively complex B(C 6 F 5 ) 3 Á2H 2 O in acetonitrile solution. 28…”

A Catalyst Platform for Unique Cationic (Co)Polymerization in Aqueous Emulsion

“…Such lack of reactivity was attributed to the complete dissociation of the Yb(OTf) 3 salt in water with the formation of a hydrated Yb cation,7 which is a weak Lewis acid. Styrene,8 cyclopentadiene,9 isoprene,10 and even acrolein11 polymerizations were performed in aqueous suspension and/or emulsion for the first time using a singular Lewis acid, B(C 6 F 5 ) 3 , which does not decompose in water 12. Despite obvious progresses in terms of reaction rates, the molar masses of synthesized polymers were still not higher than 3000 g mol −1 , a limit value above which interfacial polymerization ceases 1.…”

Cationic half‐sandwich scandium complex for the synthesis of polyisobutylene with high molecular weight under mild conditions

“…In the past decades, the application of weak Lewis acids (such as B(C 6 F 5 ) 3 , Al(C 6 F 5 ) 3 and [Ph 3 C][B(C 6 F 5 ) 4 ]), which can generate weakly coordinating counteranions, has aroused great interests in the synthesis of high M n polyisobutylene under mild conditions, because the low nucleophilicity of these counteranions can restrict side reactions in the cationic polymerization . Particularly, well‐defined group 4 metallocene complexes (Ti, Zr, and Hf) with weakly coordinated counteranions can achieve high M n polyisobutylene at mild conditions, but isobutylene conversions were limited (10–60%) .…”