Novel synthesis of symmetrical 3,3′-allyl dithioethers as photoplastic monomer precursors by equal molar rate addition of reactants and solvent controlled oligomerization

A Versatile Comonomer Additive for Radically Recyclable Vinyl-derived Polymers

Radically-formed, vinyl-derived polymers account for over 30 % of polymer production. Connected through stable carbon-carbon bonds, these materials are notoriously challenging to chemically recycle. Herein, we report universal copolymerization of a cyclic allyl sulfide (CAS) additive with multiple monomers under free-radical conditions, to introduce main-chain dynamic motifs. Backbone allyl sulfides undergo post-polymerization radical rearrangement via addition-fragmentation-transfer (AFT) that fosters both chain scission and extension. Scission is selectively induced through allyl sulfide exchange with small molecule thiyl radicals, resulting in oligomers as low as 14 % of the initial molar mass. Crucially, oligomers retain allyl sulfide end groups, enabling their extension with monomer under radical conditions. Extended, i.e., recycled, product molar mass is tunable through the ratio of monomer to oligomer, and can surpass that of the initial copolymer. Two scission-extension cycles are demonstrated in copolymers with methyl methacrylate and styrene without escalation in dispersity. In illustration of forming higher-value products, i.e., upcycling, we synthesized block copolymers through the extension of oligomers with a different vinyl monomer. Collectively, our approach to chemical recycling is unparalleled in its ability to 1) function in a variety of vinyl-derived polymers, 2) complete radical closed-loop cycling, and 3) upcycle waste material.

Synthesis of novel ([oligomethylene]alkane-α,ω-diyl) bis(diallylcarbamodithioates); monomers as precursors for RAFT photoplastic polymer networks

An efficient three-component coupling reaction of N,N-diallylamine, carbon disulfide, and bis(allyl chlorides) of the type β,ω-bis(chloromethyl)poly(glycolyl)-α,ω-dienes and other such compounds, in the presence of excess triethylamine in chloroform, has been established. The resulting mixtures gave after aqueous workup novel ([oligomethylene]alkane-α,ω-diyl) bis(diallylcarbamodithioates) that may also function as useful monomers for RAFT-based photoplastic polymer networks.