One‐Pot Precision Synthesis of AB, ABA and ABC Block Copolymers via Switchable Catalysis

Abstract

The switchable catalysis using a commercial salenMn catalyst was firstly developed and applied in the one‐pot selective copolymerization from anhydrides, epoxides, CO2 and ϵ‐caprolactone (ϵ‐CL) mixtures for the precise synthesis of AB, ABA and novel ABC block copolymers. The observed unique double switch process comprising three different polymerization cycles was rationalized by theoretical calculations. Surprisingly, the first block turned out to be an efficient macromolecular initiator for the consecutive introduction of carbonate linkages into copolymers, albeit with dominant cyclization with the catalyst alone. Further, through the selective reaction on different epoxides, the switchable copolymerization of up to five monomers was achieved yielding well‐defined multi‐block copolymers with structural diversity and functionality.

Lithium achieves sequence selective ring-opening terpolymerisation (ROTERP) of ternary monomer mixtures

“…In ROCOP, the concept of switchable catalysis has been established as a mechanistically elegant and practical tool to synthesise block-polymers with useful material properties. [69][70][71][72][73] Here a suitable catalyst rst mediates the ROP of for example cyclic esters with epoxides present in the mixture until the second ROCOP monomer (e.g. CO 2 ) is added causing immediate termination of ROP and the onset of (e.g.…”

Switchable Polymerization: A Practicable Strategy to Produce Biodegradable Block Copolymers with Diverse Properties

“…Based on this, Pang and coworkers developed a Schiff base switchable copolymerization system and applied it to the switchable copolymerization of various heterocyclic monomers for the precise synthesis of AB, ABA, and novel ABC block copolymers. [69] Theoretical calculations were performed on the observed unique double-switch process involving three distinct polymerization cycles. Notably, the first-introduced block was shown to act as an initiator for the continuous introduction of carbonate bonds into the copolymer.…”

Multidimensional Control of Repeating Unit/Sequence/Topology for One-Step Synthesis of Block Polymers from Monomer Mixtures

“…Until now, self-switchable polymerization has been applied to a variety of polymerization cycles, including cyclic ester ring-opening polymerization (ROP), ,, epoxide ROP, , epoxide/CO 2 ring-opening alternating copolymerization (ROCOP), ,, epoxide/cyclic anhydride ROCOP, − epoxide/isocyanate ROCOP, episulfide/isothiocyanate ROCOP, , and N -sulfonyl aziridines/cyclic anhydride ROCOP, , and thioanhydride/epoxide ROCOP, leading to one-step synthesis of polyester, poly­(ether- alt -ester), polyurethane, polycarbonate, polythioether- b -poly­(episulfide- alt -isothiocyanate), poly­(ester- alt -amide), and polyester- b -poly­(ester- alt -thioester), respectively. Recently, a Zr­(IV) catalyst has been reported that yields poly­(ester- alt -ether) comprising a ring-opened PA (A), followed by two ring-opened cyclic ethers such as epoxide/oxetane (B) and tetrahydrofuran (C) (−ABB– or −ABC−) .…”

“…6 Regarding the synthesis of block polymer, self-switchable polymerization is the most promising method because it applies mixture of monomers and uses a single catalyst that spontaneously connects different catalytic cycles to produce block sequence, 7−23 thereby overcoming the disadvantages of conventional procedures, e.g., sequential monomer addition approach and coupling of premade blocks. 24,25 Until now, self-switchable polymerization has been applied to a variety of polymerization cycles, including cyclic ester ringopening polymerization (ROP), 7,14,22 epoxide ROP, 22,26 epoxide/CO 2 ring-opening alternating copolymerization (ROCOP), 9,12,27 epoxide/cyclic anhydride ROCOP, 28−31 epoxide/isocyanate ROCOP, 32 episulfide/isothiocyanate ROCOP, 33,34 and N-sulfonyl aziridines/cyclic anhydride ROCOP, 35,36 and thioanhydride/epoxide ROCOP, 37 leading to one-step synthesis of polyester, poly(ether-alt-ester), polyurethane, polycarbonate, polythioether-b-poly(episulfidealt-isothiocyanate), poly(ester-alt-amide), and polyester-bpoly(ester-alt-thioester), respectively. Recently, a Zr(IV) catalyst has been reported that yields poly(ester-alt-ether) comprising a ring-opened PA (A), followed by two ringopened cyclic ethers such as epoxide/oxetane (B) and tetrahydrofuran (C) (−ABB− or −ABC−).…”