One‐Step Sequence‐Selective Synthesis of Block Copolyester from Mixed Phthalic Anhydride, Cyclohexene Oxide, and δ‐Valerolactone

Abstract

One-step synthesis of well-defined block copolymer is of great fundamental and practical values. Here, an aromatic-aliphatic block copolyester is one-step synthesized from the mixture of phthalic anhydride (PA), cyclohexene oxide (CHO), and 𝜹-valerolactone (𝜹-VL) at room temperature in the presence of a metal-free Lewis pair catalyst consisting of triethylborane and excess phosphazene base. Alcohol-initiated ring-opening alternating copolymerization of PA and CHO occurs first and selectively because of the overwhelmingly higher activity of PA than CHO and 𝜹-VL toward the reaction with base-activated hydroxy species. Only after full conversion of PA is reached can ring-opening polymerization of 𝜹-VL occur from the terminus of the aromatic polyester so that a well-defined (AB) n C m type block copolyester is formed. The two polymerizations are both highly chemoselective without homopolymerization of CHO or extensive transesterification reactions. Owing to the sequence-selective and living characteristics of the terpolymerization, hepta-and undecablock copolyesters with controlled molar mass and low dispersity are obtained through addition of the three-component monomer mixture in batches. Applicability of the method to propylene oxide and 𝝐-caprolactone is also examined.

Borane catalysis for epoxide (co)polymerization

“…Similarly, the repeated addition of batches of such three-component monomer mixtures can lead to even larger multiblock copolymers, for example hepta- or undecablockcopolymers. 126…”

“…It should be noted that this example underlines the optimum borane loading for cyclic ester or epoxide selectivity is dependent on the chemical nature of both and potentially the pK a of the organobase (compare Scheme 10 for an example addressing VL and PO with tBu-P 2 as organobase, respectively). 63,126 If the excess of borane is further enhanced, then the expected increase of PO conversion and decrease of lactide conversion rate entails a tapering of the block structure (3 : 1 ratio). Similarly, the repeated addition of batches of such three-component monomer mixtures can lead to even larger multiblock copolymers, for example hepta-or undecablockcopolymers.…”

“…Similarly, the repeated addition of batches of such three-component monomer mixtures can lead to even larger multiblock copolymers, for example hepta-or undecablockcopolymers. 126 Wang and co-workers also succeeded in the preparation of well-defined triblock copolymers (Đ M < 1.20) from mixtures of epoxides, anhydrides, rac-LA and vinyl monomers (such as styrene or methyl methacrylate). 127 In this case Et 3 B/DBU was employed alongside a specific RAFT transfer agent (trithiocarbamate with a carboxylic group) so that the living radical Scheme 14 One-pot terpolymerization resulting in different polymer architectures depending on catalyst stoichiometry.…”

Self-Switchable Polymerization: A Smart Approach to Sequence-Controlled Degradable Copolymers

“…And the polymer featuring both alkyne and vinyl groups could undergo independent functionalization through azide–alkyne cycloaddition and thiol–ene chemistry. Following this, efforts have been made to expand the scope of catalysts to bimetallic aluminum complexes 4 , Lewis pairs, , and alkali metal carboxylates 11 . Moreover, this switchable technique was also conjugated with RAFT polymerization of vinyl monomers to bridge three types of polymerization cycles .…”