Chemically Recyclable Polymer System Based on Nucleophilic Aromatic Ring-Opening Polymerization

Abstract

The development of chemically recyclable polymers with desirable properties is a long-standing but challenging goal in polymer science. Central to this challenge is the need for reversible chemical reactions that can equilibrate at rapid rates and provide efficient polymerization and depolymerization cycles. Based on the dynamic chemistry of nucleophilic aromatic substitution (S N Ar), we report a chemically recyclable polythioether system derived from readily accessible benzothiocane (BT) monomers. This system represents the first example of a well-defined monomer platform capable of chain-growth ring-opening polymerization through an S N Ar manifold. The polymerizations reach completion in minutes, and the pendant functionalities are easily customized to tune material properties or render the polymers amenable to further functionalization. The resulting polythioether materials exhibit comparable performance to commercial thermoplastics and can be depolymerized to the original monomers in high yields.

Design of depolymerizable polymers toward a circular economy

“…101,102 Gutekunst and co-workers have taken this idea of S N Ar reversibility and combined it with ROP to facilitate depolymerizability using a cyclic aromatic thioether denoted as S N ArROP (Scheme 2). 103 The resulting polythioether has a T g of 79.5 °C and expressed mechanical properties comparable to commonly used thermoplastics such as polyethylene, poly vinyl acetate, and poly vinyl chloride. The depolymerization proceeded through backbone cleavage with the addition of thiol and DBU followed by backbiting, showing a successful isolated yield of 85% at 90 °C and a concentration of 10 mg mL −1 .…”

Modulating Polymerization Behaviors of Ether–Ester Monomers and Physicochemical Properties of Poly(ether-alt-ester)s by Heteroatom Substitutions

“…Oxygen-by-sulfur substitution, emerging early in the evolution of living beings with the thiolation of tRNA nucleobases and participating in peptide synthesis across all domains of life, can significantly improve the properties of the synthetic polymers as well. , Beyond the intrinsically outstanding optical, electrical, and thermal properties, thio-modification also endows the polymers with chemical recyclability. ,− Bridged bicyclic thiolactones were reported to produce polythioesters with complete recyclability and tunable properties. , Penicillamine-derived β-thioacetone with gem-dimethyl substitutions exhibits a near equilibrium (de)­polymerization thermodynamic, which allows for regulating both the forward polymerization of β-thioacetones and backforward depolymerization of polythioesters in a highly controlled fashion . γ-Thionobutyrolactone, obtained by thio-modification of γ-butyrolactone, easily undergoes irreversible ROP driven by S/O isomerization at an industrially relevant temperature, affording polymers with external-stimuli-triggered degradability .…”

Controlled and Regioselective Ring-Opening Polymerization for Poly(disulfide)s by Anion-Binding Catalysis

“…Sulfur-containing polymers exhibit a myriad of unique properties and functions, leveraged by the desirable physical properties of the S atom and rich reactivity profile of the element. Sulfur-containing polymers come in many shapes and forms, including thioesters, − thiocarbonates, thioethers, thioamides, thioureas, disulfides, trisulfides, and polysulfides. , In particular, disulfides (RS–SR) show a gamut of stimuli-responsive properties owing to the dynamic covalent S–S bonds. Its dynamic covalent nature is robust and media-tolerant, , making it a popularly sought-after motif in designing functional polymers and already so in nature’s macromolecules.…”