Direct Organocatalytic Ring‐Opening Polymerizations of Lactones

Abstract

Abstract:We have developed a novel organocatalytic, direct synthesis of aliphatic polyesters. The synthesis was based on a novel direct organic acid-catalyzed living ring-opening polymerization (ROP) of ecaprolactone and d-valerolactone with benzyl alcohol as the initiator. The organic acid-catalyzed ROPs were performed without solvent and the catalyst was recovered by precipitation of the polyester products. In addition, they were operationally simple, inexpensive and environmentally benign. Organic acid catalysis provides a new entry for the synthesis of valuable biodegradable materials as well as polyesters for biomedical applications.

Improving the reproducibility of chemical reactions on the surface of cellulose nanocrystals: ROP of ε-caprolactone as a case study

“…In this work, we chose to use a benign organic acid, namely citric acid, while performing all reactions in bulk, in line with the green objectives of our group, to study the reproducibility of the surfaceinitiated ROP of e-caprolactone from the surface of cellulose nanowhiskers. Carboxylic acids (lactic acid Persson et al 2004;Casas et al 2004, tartaric acid Casas et al 2004Hafrén andCórdova 2005, hexanoic acid Persson et al 2004;Casas et al 2004, propanoic acid Rindlav-Westling andGatenholm 2003;Persson et al 2004;Casas et al 2004-hydroxyhexanoic acid Persson et al 2004, citric acid Casas et al 2004) as well as amino acids (Casas et al 2004) (glycine, proline, serine) have been used before to catalyse the ROP of e-caprolactone using monosaccharides ) (methyl b-D-glucopyranoside), disaccharides ) (sucrose), or trisaccharides ) (raffinose) as initiators and SI-ROP from cotton fibres has also been performed (Hafrén and Córdova 2005). Casas and co-workers proposed a monomer activated mechanism for this polymerisation (Casas et al 2004).…”

A Recoverable, Metal-Free Catalyst for the Green Polymerization of ε-Caprolactone

“…11 These reactions show characteristics of a controlled, living reaction (e.g., conversion shows a linear relationship to reaction time, molecular weight shows a linear dependence on conversion, and the resulting polymers show a low polydispersity). 3,11,46 Other purely organic systems that display catalytic activity include natural amino acids, 9 organic acids, 47 and acid/alcohol systems. 13 Unfortunately, these catalysts are all homogeneous species 48 that, while not contaminating the polymer with metal residue, are not easily recoverable from the reaction mixture, making catalyst recovery and recycle problematic.…”

Thiourea binding with carboxylic acid promoted cationic ring-opening polymerization

“…Strong Brønsted acid featured with fast reaction rate usually accompanied with drawbacks in poor control. Weak Brønsted acid such as tartaric, citric and L-Lactic acid [47][48][49] showed limited efficiency in bulk polymerization at high temperature (120 °C), solution polymerization was not feasible. Between the strong and weak ones, trifluoroacetic acid (TFA) as a Brønsted acid has been successful in ROPs of ε-caprolactone [46] and trimethylene carbonates [50], however, ε-CL polymerized in bulk condition at elevated temperatures; similarly, poly(trimethylene carbonates) (PTMC) was obtained as oligomers with poor molecular weight distributions [50], and TFA as Bronsted acid due to its pseudoliving character in ROP of TMC [51].…”