Triethylborane-Assisted Synthesis of Random and Block Poly(ester-carbonate)s through One-Pot Terpolymerization of Epoxides, CO2, and Cyclic Anhydrides

Vamshi K Chidara,Nikos Hadjichristidis,Senthil K Boopathi,Xiaoshuang Feng,Yves Gnanou

doi:10.1021/acs.macromol.0c02825

Vamshi K Chidara, Nikos Hadjichristidis + Show 3 more

Open Access

https://doi.org/10.1021/acs.macromol.0c02825

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Abstract

Poly(ester-carbonate) copolymers were synthesized through triethylborane (TEB)-activated, one-pot copolymerization of epoxides with anhydrides (AH) and CO₂. Depending upon the feeding ratio of AH to the epoxides, poly(ester-carbonate) copolymers with random and tapered ester structures could be derived due to the much higher reactivity of AH toward growing oxanions compared to the reactivity of CO₂. Anhydrides like succinic anhydride (SA) and phthalic anhydride (PA) when tried in terpolymerization with epoxides, like propylene oxide (PO) and cyclohexene oxide (CHO), and CO₂ indeed exhibited such high reactivities in comparison to CO₂ that tapered block structures were eventually obtained for high feeding ratios of AH to PO and random copolymers for the AH-to-epoxide feeding ratio lower than 10%. Terpolymerization with different feeding ratios of anhydrides to epoxides was thus systematically investigated. In an alternate path, diblock poly(ester-b-carbonate)s were prepared by sequential copolymerization of epoxide/anhydride and epoxide/CO₂. All of the obtained copolymers were characterized by ¹H nuclear magnetic resonance (NMR), diffusion-ordered spectroscopy (DOSY), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). The structures and properties of copolymers obtained by terpolymerizations and block copolymerizations were compared.

Highlights

Since the pioneering report of Inoue et al in 1969,1 the ringopening copolymerization of epoxides and CO2, a nontoxic, cheap, and abundant greenhouse gas, has proven to be a versatile route for the synthesis of aliphatic polycarbonates
During the past 2 decades, great progress has been witnessed in efficiently producing polycarbonates with different catalysts including heterogeneous and homogeneous ones and even with a recently reported metal-free system.[2−4] the two most studied polycarbonates, i.e., poly(propylene carbonate) (PPC) and poly(cyclohexene carbonate) (PCHC) that are generated due to the easy availability of their epoxide monomers propylene oxide (PO) and cyclohexene oxide (CHO), suffer from their relatively low thermal−mechanical properties such as low glass transition temperature, low tensile strength, and brittle nature
Based on the above observations, the copolymerization reactivities with epoxide in the presence of CO2 follow the order succinic anhydride (SA) > phthalic anhydride (PA) > CO2, similar to the results reported by Darensbourg in the case of terpolymerization of CHO/AH/CO2; the reactivity of aliphatic anhydrides is higher than that of aromatic ones.[22]

Summary

Introduction

Since the pioneering report of Inoue et al in 1969,1 the ringopening copolymerization of epoxides and CO2, a nontoxic, cheap, and abundant greenhouse gas, has proven to be a versatile route for the synthesis of aliphatic polycarbonates.

Results

Conclusion