Mechanistic study of boron trifluoride catalyzed ε‐caprolactone polymerization in the presence of glycerol

Abstract

Boron trifluoride catalyzed e-caprolactone polymerization in the presence of glycerol can produce poly(e-caprolactone) with a high weight-average molecular weight and a broad molecular weight distribution. This article reports an investigation of the polymerization mechanism to determine the formation of these molecular weight features through a study of the polymerization kinetics and the molecular structure with NMR. The polymerization proceeds via an activated monomer mechanism, resulting in polymer molecules with hydroxyl chain ends. The broad molecular weight distribution can be attributed to the etherification reactions between hydroxyl chain ends.

Activated Monomer Mechanism (AMM) in Cationic Ring-Opening Polymerization. The Origin of the AMM and Further Development in Polymerization of Cyclic Esters

“…Nevertheless, several other strong electrophiles were also applied, and apparently, there could be a myriad of such activators, more or less successful. We quote three examples, two related to traditional CROP, namely, BF 3 and Al­(TfO) 3 , and one more unusual, with metal oxides as catalysts (including Co 2 O 3 , possibly carcinogenic to humans) and claiming synthesis of PCL and PLA with M n over 10 5 g·mol –1 and end groups resulting from initiation with H 2 O …”

Mechanistic study of Sn(Oct)2‐catalyzed ε‐caprolactone polymerization using Sn(Oct)2/BF3 dual catalyst

“…12,13 The spectrum of the polymer using neat BF 3 catalyst has a triplet at d ¼ 3.4 ppm, which is due to an ether bond formed by the reaction between two hydroxyl end groups. 14 The presence of hydroxyl end groups in the polymer molecules indicated by the NMR spectra is the imprint of water initiator. The reaction system containing neat BF 3 catalyst had no induction period, whereas there was an induction period when BF 3 and Sn(Oct) 2 coexisted in the system.…”

Polyglycerol Hyperbranched Polyesters: Synthesis, Properties and Pharmaceutical and Biomedical Applications

“…When glycerol is used to initiate the polymerization, a three-arm poly(glycerol ε-caprolactone) (PGCL) polyester is produced (Scheme 10). For PGCL synthesis the most often used catalyst has been tin(II) 2-ethylhexanoate or stannous octoate, Sn(Oct)2 [203][204][205][206][207][208][209][210][211], however, acidic (BF3•O(CH3)2) [212,213], and enzymatic (Novozym 435) [214,215] catalysis have been explored as well. The polymerization has been carried out between 110 °C and 130 °C when Sn(Oct)2 was used (about 48 h polymerization) or at lower temperatures when Novozym 435 (70 °C) or BF3O•(CH3)2, (80 °C) were used.…”

“…The polymerization has been carried out between 110 • C and 130 • C when Sn(Oct) 2 was used (about 48 h polymerization) or at lower temperatures when Novozym 435 (70 • C) or BF 3 O•(CH 3 ) 2 , (80 • C) were used. The PGCL polymers were characterized by GPC [203,[206][207][208][209][210][212][213][214][215], FTIR [203,207,209,210,215], NMR [203,[206][207][208][209][210][212][213][214][215], DSC [203,206,212,214,215], and X-ray diffraction [206,215].…”

“…However, the degree of crystallinity decreased when increasing the number of arms. BF 3 , which is a strong Lewis acid, can also initiate the ring opening polymerization of ε-caprolactone via a cationic mechanism [213]. Gly (0.018-0.073 mol/dm 3 ) and CL were polymerized at 80 • C for 72 h using BF 3 (0.0095 mol/dm 3 ) as catalyst.…”