One-Step Synthesis of Linear and Hyperbranched CO<sub>2</sub>-Based Block Copolymers via Organocatalytic Switchable Polymerization
Maoji Zhao, Shuaishuai Zhu, Zhang Guochao, Yong Wang, Yonggui Liao, Jing Xu, Xingping Zhou, Xiaolin Xie
Abstract
CO 2 -based block copolymers are gaining significant momentum as high-value-added and functional materials. However, current synthetic achievements mainly rely on well-designed organometallic catalysts and only give access to linear polymeric products. Herein, we report the organocatalytic three-component polymerization of propylene oxide (PO), phthalic anhydride (PA), and CO 2 mediated by commercial Lewis pairs composed of triethyl borane (Et 3 B) and organic bases, wherein the chemoselectivity over the reaction and Lewis basicity of the cocatalysts exhibit a negative correlation. Notably, the interplay of Et 3 B and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) bridges and discriminates the ring-opening copolymerization (ROCOP) of PO/PA and ROCOP of PO/CO 2 without interferences, thus affording poly(propylene phthalate)- b -poly(propylene carbonate) (PPE- b -PPC) with linear and hyperbranched topologies by using benzyl alcohol and 1,3,4-benzene tricarboxylic anhydride as the chain transfer agent, respectively. Notably, the formation of undesirable cyclic byproducts was completely circumvented by rationally modulating the Et 3 B/CTA ratio. Moreover, the effect of topology on the viscosity, glass transition temperature, and thermal stability of PPE- b -PPC has been exploited.