Cationic copolymerization of racemic -β-butyrolactone with L,L-lactide: One-pot synthesis of block copolymers

Abstract

Cationic copolymerization of racemic‐β‐butyrolactone (β‐BL) with l,l‐lactide (LA) initiated by alcohol and catalyzed by trifluoromethanesulfonic acid proceeding by activated monomer (AM) mechanism was investigated. Although both comonomers were present from the beginning in the reaction mixture, polymerization proceeded in sequential manner, with poly‐BL formed at the first stage acting as a macroinitiator for the subsequent polymerization of LA. Such course of copolymerization was confirmed by following the consumption of both comonomers throughout the process as well as by observing the changes of growing chain‐end structure using 1H NMR. 13C NMR analysis and thermogravimetry revealed the block structure of resulting copolymers. The proposed mechanism of copolymerization was confirmed by the studies of changes of 1H NMR chemical shift of acidic proton in the course of copolymerization, providing an indication that indeed protonated species and hydroxyl groups are present throughout the process, as required for AM mechanism. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4873–4884

Organocatalysis applied to the ring‐opening polymerization of β‐lactones: A brief overview

“…When the propagation proceeds with an attack of the oxygen atom of the terminal hydroxyl group on the carbonyl carbon atom in the protonated monomer molecule, a competing mechanism, named the “activated monomer” (AM) mechanism, could occur . In 2013, Kubisa et al performed the homopolymerization of BL in CH 2 Cl 2 at room temperature with isopropanol as the initiator and triflic acid as the catalyst . The authors elegantly demonstrated that for [BL]/[ROH] ratios <30, PBL chains were obtained with a good control in terms of the molar masses and the end‐groups' nature (initiation from isopropanol only) through an AM mechanism.…”

Polylactides—an overview

“…Not only poly[(L,L)‐lactide] but also copolymers of (L,L)‐lactide and ε ‐caprolactone or β ‐butyrolactone were synthesized according to the activated monomer mechanism . This type of polymerization allowed also synthesis of poly[(L,L)‐lactide] macromonomers and poly[(L,L)‐lactide] with reactive alkyne group …”

Tuning thermal properties and microphase separation in aliphatic polyester ABA copolymers

“…Due to the difficulty in poly-merising β-butyrolactone (β-BL), 4 both the homopolymerisation and copolymerisation of β-BL have seen limited study. [16][17][18][19][20] Our group recently reported the copolymerisation of rac-β-BL and rac-lactide 21 Interestingly, bulk copolymerisation with 3 at 120°C, the system favored incorporation of lactide over β-BL despite the rate of β-BL homopolymerisation being significantly higher than for lactide. 14 The product had random monomer incorporation, high molecular weight and a broad dispersity (Đ = 1.7).…”