Oxygen‐Triggered Switchable Polymerization for the One‐Pot Synthesis of CO₂‐Based Block Copolymers from Monomer Mixtures

Abstract

Switchable polymerization provides the opportunity to regulate polymer sequence and structure in ao ne-pot process from mixtures of monomers.Herein we report the use of O 2 as an external stimulus to switch the polymerization mechanism from the radical polymerization of vinyl monomers mediated by (Salen)Co III À R[ Salen = N,N'-bis(3,5-di-tertbutylsalicylidene)-1,2-cyclohexanediamine;R = alkyl] to the ring-opening copolymerization (ROCOP) of CO 2 /epoxides. Critical to this process is unprecedented monooxygen insertion into the CoÀCb ond, as rationalized by DFT calculations, leading to the formation of (Salen)Co III À O À Ra sa na ctive species to initiate ROCOP.D iblock poly(vinyl acetate)-bpolycarbonate could be obtained by ROCOP of CO 2 /epoxides with preactivation of (Salen)Co end-capped poly(vinyl acetate). Furthermore,ap oly(vinyl acetate)-b-poly(methyl acrylate)-b-polycarbonate triblock copolymer was successfully synthesized by a( Salen)cobalt-mediated sequential polymerization with an O 2 -triggered switchinaone-pot process.

Carbon dioxide copolymers: Emerging sustainable materials for versatile applications

“…For example, Lu and coworkers employed a bifunctional (salen)Co() catalyst for PO/CHO/CO 2 terpolymerization, resulting terpolymers of only one thermolysis peak whose T g was adjustable between 42 and 118°C simply by controlling the molar fraction of PCHC 103 . Block copolymerization is also chosen to adjust the performance of PPC, while CO 2 ‐based block copolymers with various molecular architectures have been designed and synthesized, for example, Wang and coworkers described a one‐pot sequential construction of a block copolymer from PO/CO 2 and vinyl monomers by oxygen‐triggered switchable polymerization 104 . Another effective way to tune the material property is to form cross‐linked networks by interconnecting polymer chains via covalent bonds or ionic bonds, for example, terpolymerization of CO 2 , PO, and allyl glycidyl ether produced UV irradiation cross‐linkable PPC with improved mechanical performance 68 .…”

Aluminum Porphyrin Complex Mediated Auto-Tandem Catalysis for One-Pot Synthesis of Block Copolymers

“…[28][29][30][31][32][33] Recently, our group reported one-pot synthetic protocols based on the switchable catalysis of cobalt salcy [bis(salicylaldimine)] complexes involving ring-opening copolymerization (ROCOP) of epoxides, CO 2 , and anhydrides and organometallic-mediated radical polymerization (OMRP) using oxygen or carbon monoxide as external stimuli, which can be classified as assisted tandem catalysis. 34,35 To the best of our knowledge, the only example utilizing auto-tandem catalysis to regulate block sequence was contributed by Grubbs et al, 36 wherein a multifunctional ruthenium complex could concurrently or sequentially mediate ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). Since the seminal work by Boyer's group, [37][38][39][40][41][42][43][44][45][46] divalent metalloporphyrins such as Zinc (II) mesotetraphenylporphine [(TPP)Zn II ] and chlorophyll (TPP)Mg II have been widely used as photocatalysts for photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization, which allow for temporal and spatial control over the chain propagation processes.…”

One-Pot Synthesis of Hyperbranched Polymers via Visible Light Regulated Switchable Catalysis

“…[35][36][37] Our group rst demonstrated the quantitative transformation between Co-O and Co-C bonds, and thereby developed switchable catalytic systems comprising ROCOP of epoxide/CO 2 /cyclic anhydride and organometallic mediated radical polymerization (OMRP) of vinyl monomers, which gave facile access to copolymers connecting polyacrylates or poly(vinyl acetate) with the oxygenate blocks (Scheme 1A). 38,39 Very recently, we successfully synthesized cyclic CO 2 -based polycarbonates and polyesters in a one-pot process via cobalt-mediated switchable catalytic transformation from ROCOP of epoxide/CO 2 /cyclic anhydride to intramolecular radical cyclization (Scheme 1B). 40 Due to the globular and dendritic architectures, hyperbranched polymers (HBPs) display unique structures and properties such as abundant functional groups, intramolecular cavities, low viscosity, and high solubility, showing great potential in applications associated with mass/energy transfer, dissipation, and distribution.…”