ABC and ABAB Block Copolymers by Electrochemically Controlled Ring-Opening Polymerization

Abstract

An electrochemically controlled synthesis of multiblock copolymers by alternating the redox states of (salfan)Zr-(O t Bu) 2 (salfan = 1,1′-di(2-tert-butyl-6-N-methylmethylenephenoxy)ferrocene) is reported. Aided by electrochemistry with a glassy carbon working electrode, an in situ potential switch alters the catalyst's oxidation state and its subsequent monomer (Llactide, β-butyrolactone, or cyclohexene oxide) selectivity in one pot. Various multiblock copolymers were prepared, including an ABAB tetrablock copolymer, poly(cyclohexene oxide-b-lactide-bcyclohexene oxide-b-lactide), and an ABC triblock copolymer, poly(hydroxybutyrate-b-cyclohexene oxide-b-lactide). The polymers produced using this technique are similar to those produced via a chemical redox reagent method, displaying moderately narrow dispersities (1.1−1.5) and molecular weights ranging from 7 to 26 kDa.

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

“…And it further shows far-reaching implications including synthesizing sophisticated sequences with exquisite functions . With external switching agents such as water, oxygen, carbon monoxide, redox reagents, etc., block copolymers could be produced through in situ transformation of active propagating species, and insightful reviews can be found elsewhere. , Modulation by external fields including electrochemical , and light-controlled polymerizations are also novel and powerful switching techniques, which could produce distinct block copolymers from monomer mixtures. Summary of polymerization under various external fields can be found in another excellent review .…”

Organocatalytic orthogonal ATRP and ring-opening polymerization using a single dual-function photocatalyst

“…and often showed their unique properties and superiority over the corresponding homopolymers. 9–17 Accordingly, the development of effective orthogonal polymerization systems has attracted considerable research interest in the past few years, which are highly desirable in both academia and industry. 18–22…”

“…and often showed their unique properties and superiority over the corresponding homopolymers. [9][10][11][12][13][14][15][16][17] Accordingly, the development of effective orthogonal polymerization systems has attracted considerable research interest in the past few years, which are highly desirable in both academia and industry. [18][19][20][21][22] The reversible-deactivation radical polymerization (RDRP) method represents a powerful tool for the precise construction of macromolecules with a predictable molecular mass, low dispersity, high end-group fidelity, and advanced complex structures [23][24][25][26][27][28][29][30] and could serve as a useful and versatile component in orthogonal polymerization.…”

“…[18][19][20][21][22] The reversible-deactivation radical polymerization (RDRP) method represents a powerful tool for the precise construction of macromolecules with a predictable molecular mass, low dispersity, high end-group fidelity, and advanced complex structures [23][24][25][26][27][28][29][30] and could serve as a useful and versatile component in orthogonal polymerization. [15][16][17][18][19][26][27][28][29][30][31][32][33][34] For example, as early as 1998, Jérôme, Hedrick and co-workers 31 demonstrated the one-pot preparation of block and graft copolymers by combining nitroxide-mediated living free-radical polymerization (NMP) and ring-opening polymerization (ROP) with the help of Sn and Al metal complexes, but high polydispersity indices were observed even with this dual-living polymerization strategy. In 2005, the Howdle group disclosed a successful combination of conventional metal-based atom transfer radical polymerization (ATRP) and enzymatic ROP using supercritical carbon dioxide as a solvent.…”

Simple and Rapid Access toward AB, BAB and ABAB Block Copolyesters from One-Pot Monomer Mixtures Using an Indium Catalyst

“…When different monomer classes, such as lactones, epoxides/CO 2 , or carboxyanhydrides, are combined in ring-opening copolymerizations, , distinct reactivity differences of the metal chain end group in the respective catalytic cycles enable high chemoselectivity and simple access to block copolymers. − In contrast to that, sequence control from one-pot mixtures of the same monomer class is highly challenging due to similar reactivity . Redox-controlled “on/off” switching in ROP of one specific cyclic ester monomer is achieved with an increasing number of catalysts, − yet, establishing orthogonal monomer reactivity for two different lactones to generate block copolyesters is rarely reported. , For example, the synthesis of a block copolymer microstructure from an l -lactide ( l -LA)/ ε -caprolactone ( ε -CL) feedstock has been achieved with a redox-switchable titanium catalyst . Using a different approach, stereoselective polymerization catalysts allowed for the synthesis of alternating sequence-controlled polyesters when mixed monomers of opposite stereochemistry were employed. , However, the addition of oxidants and reductants or the use of enantiopure monomer mixtures makes these approaches experimentally challenging.…”