All-Polycarbonate Thermoplastic Elastomers Based on Triblock Copolymers Derived from Triethylborane-Mediated Sequential Copolymerization of CO2 with Various Epoxides.

Mingchen Jia,Sanjay Rastogi,Xiaoshuang Feng,Dongyue Zhang,Yves Gnanou,Gijs W De Kort,Nikos Hadjichristidis,Carolus H R M Wilsens

doi:10.1021/acs.macromol.0c01068

Mingchen Jia, Sanjay Rastogi + Show 6 more

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https://doi.org/10.1021/acs.macromol.0c01068

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Abstract

Various oxirane monomers including alkyl ether or allyl-substituted ones such as 1-butene oxide, 1-hexene oxide, 1-octene oxide, butyl glycidyl ether, allyl glycidyl ether, and 2-ethylhexyl glycidyl ether were anionically copolymerized with CO2 into polycarbonates using onium salts as initiator in the presence of triethylborane. All copolymerizations exhibited a “living” character, and the monomer consumption was monitored by in situ Fourier-transform infrared spectroscopy. The various polycarbonate samples obtained were characterized by 1H NMR, GPC, and differential scanning calorimetry. In a second step, all-polycarbonate triblock copolymers demonstrating elastomeric behavior were obtained in one pot by sequential copolymerization of CO2 with two different epoxides, using a difunctional initiator. 1-Octene oxide was first copolymerized with CO2 to form the central soft poly(octene carbonate) block which was flanked by two external rigid poly(cyclohexene carbonate) blocks obtained through subsequent copolymerization of cyclohexene oxide with CO2. Upon varying the ratio of 1-octene oxide to cyclohexene oxide and their respective ratios to the initiator, three all-polycarbonate triblock samples were prepared with molar masses of about 350 kg/mol and 22, 26, and 29 mol % hard block content, respectively. The resulting triblock copolymers were analyzed using 1H NMR, GPC, thermogravimetric analysis, differential scanning calorimetry, and atomic force microscopy. All three samples demonstrated typical elastomeric behavior characterized by a high elongation at break and ultimate tensile strength in the same range as those of other natural and synthetic rubbers, in particular those used in applications such as tissue engineering.

Highlights

The copolymerization of CO2 with epoxides has received extensive attention as it allows one to transform a naturally abundant C1 resource, namely greenhouse gas, into degradableCpOol2y,mewrhicichmaitseriaallsso.1−a3Since its discovery in the 1969,4 significant progress has been made mainly during the past two decades in terms of activity and selectivity of the catalysts developed
Heterogeneous catalysts include zinc glutarate (ZnGA) or carboxylates (ZnCA), double metal cyanides (DMC), as well as rare earth metal ternary catalysts; on the other hand homogeneous catalysts are based on first row transition metals such as Cr, Co, Zn, Fe, or earth abundant metals such as Al, Mg, etc. associated with different ligands.[3,5−10] numerous catalysts have been developed over time, none of them was designed to allow the copolymerization of CO2 indiscriminately with all epoxides available; either the metal or the ligand had to be modified depending upon the epoxides chosen
From the literature published so far on TEBmediated synthesis of polycarbonates it appears that the success of the copolymerization of epoxides with CO2 depends on the amount of TEB needed, which varies with the epoxides considered

Summary

Introduction

The copolymerization of CO2 with epoxides has received extensive attention as it allows one to transform a naturally abundant C1 resource, namely greenhouse gas, into degradableCpOol2y,mewrhicichmaitseriaallsso.1−a3Since its discovery in the 1969,4 significant progress has been made mainly during the past two decades in terms of activity and selectivity of the catalysts developed. The copolymerization of CO2 with epoxides has received extensive attention as it allows one to transform a naturally abundant C1 resource, namely greenhouse gas, into degradable. Kim et al first screened the activity of heterogeneous Zn−Co(III) DMC catalyst for the copoly-. They obtained polycarbonates with high ether contents.[11] Zhang et al on the other hand utilized the same heterogeneous Zn−Co(III) DMC catalyst to investigate the copolymerization behavior of CO2 with alkyl-substituted epoxides; the polycarbonates obtained in the latter case exhibited >90% of carbonate content but for epoxides such as ethylene oxide (EO) and propylene oxide (PO), the carbonate content in poly(ethylene carbonate) (PEC) and poly(propylene carbonate) (PPC) dropped to 55% and 73%, respectively.[12]

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