Article Open Access

Metal-Free Lewis Pair Catalysts for a One-Pot Terpolymerization of Propylene Oxide, ʟ-Lactide and CO2

Sustainable Polymer & Energy. 2023, 1(1), 10002; https://doi.org/10.35534/spe.2023.10002
Shuxian Ye 1,    Jiaxin Liang 1,    Yansong Ren 1,    Shuanjin Wang 1,    Dongmei Han 4,    Sheng Huang 1,    Zhiheng Huang 1,    Min Xiao 1, *    Yuezhong Meng 1, 2, 3, 4, *   
1
The Key Laboratory of Low-carbon Chemistry & Energy Conservation of Guangdong Province/State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China
2
Institute of Chemistry, Henan Academy of Sciences, Zhengzhou 450000, China
3
Research Center of Green Catalysts, College of Chemistry, Zhengzhou University, Zhengzhou 450001, China
4
School of Chemical Engineering and Technology, Sun Yat-sen University, Guangzhou 510275, China
*
Authors to whom correspondence should be addressed.

Received: 27 Nov 2022    Accepted: 11 Jan 2023    Published: 30 Jan 2023   

Abstract

Multiblock and di-/tri-block copolymers are successfully synthesized for the first time via the metal-free terpolymerization of propylene oxide (PO), ʟ-lactide (LA) and CO2 in one-pot/one-step and one-pot/two-step protocols respectively. Firstly, triethyl borane (TEB) and bis(triphenylphosphine)iminium chloride (PPNCl) Lewis pair is employed in the ring-opening polymerization of LA, wherein the catalytic efficiency is significantly correlated to the TEB/PPNCl feed ratio. Next, a series of TEB/base pairs are selected to synthesize the PO/LA/CO2 terpolymer (PPCLA) in one-pot/one-step strategy. In PPCLA synthesis, LA exhibits the fastest reaction rate but the severe transesterification is almost unavoidable, resulting in low molecular weight products. In order to prepare high-molecular-weight terpolymers, a one-pot/two-step methodology has to be applied. By this method, the copolymerization of PO/CO2 proceeds first to form poly(propylene carbonate) (PPC) macroinitiators, which triggers the polymerization of LA to polylactide (PLA), leading to PLA-PPC or PLA-PPC-PLA block copolymers. The synthesized PLA-PPC-PLA block copolymers display an improved thermal stability compared with PPC.

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