Aspects of the cationic polymerization of ε-caprolactone in the presence of alcohols

A Catalytic Approach for Cationic Living Polymerization: Sc(OTf)3-Catalyzed Ring-Opening Polymerization of Lactones

“…Caution should be exercised that ROH such as BnOH and H 2 O does not belong to the classical category of “initiators”, because it is inert to CL by itself, and the reactive species here is the electrophilic complex 1 . Polymerization of lactones via an activated monomer mechanism had been reported using Et 3 O + ·PF 6 - or Et 3 O + ·SbF 6 - in the presence of ROH, where the related results were observed. Nonetheless, the concept of the catalytic approach for cationic living polymerization had not been realized, and those had also been limited to synthesis of relatively small molecular weight polymer ( M n ≤ 3000) with an unsatisfactory MWD ( M w / M n = 1.3 1 ) in CL polymerization 13 as far as we know.…”

“…The plausible mechanism is shown in Scheme as an activated monomer mechanism. − Coordination of CL to Sc(OTf) 3 affords the cationic complex 1 , followed by the electrophilic attack to ROH to produce ε-hydroxy ester 2 . It was supported by the fact that BnOH was consumed at the initial stage of polymerization by TLC analysis and also by formation of benzyl ester at polymer termini.…”

Synthesis and characterization of poly(3,3 bis(azidomethyl)oxetane-co-?-caprolactone)s

“…Thus, contrary to the anionic process, the cationic polymerization of lactones rarely exhibits a living mechanism. 17 However, Belen'kaya et al 20 investigated the cationic polymerization of -CL initiated by (…”

“…Considering, on the one hand, these results and, on the other hand, the proposed mechanisms for the cationic polymerization of oxetanes 1,3,[11][12][13][14] and lactones, 20 it is reasonable to assume that the BF 3 : OEt 2 catalyst first reacts with one OH end group of BDO to form an adduct that is then involved in the initiation step. The fact that the polymerization of BCMO and -CL leads to oligomers with a functionality close to 2 is an indication that the polymerization can proceed through an activated-monomer mechanism for BCMO and an hydroxo-mechanism for -CL, without cyclization, at least for a polymer molecular weight of a few hundred.…”