Design of functional isocyanate-free poly(oxazolidone)s under mild conditions

Abstract

Polyoxazolidones, i.e. high-performance polymers bearing cyclic carbamate linkages, were recently obtained by a non-isocyanate route under mild conditions. Herein, we report the preparation of polyoxazolidones bearing thioether linkages, which offer multiple opportunities for facile chain functionalization. The process consists in the chemical upcycling of CO₂-based poly(oxo-carbonate)s by aminolysis with allylamines. At room temperature, a poly(oxo-carbonate) is completely decomposed into an allyl-functionalized bis(oxazolidone) which is then copolymerized with dithiols by UV-initiated thiol–ene polymerization. The allyl-functionalized bis(oxazolidone) monomer is also quantitatively obtained by reacting an allylamine with a CO₂-based bis(alkylidene cyclic carbonate). A library of poly(oxazolidone-co-thioether) copolymers is easily accessible by varying the nature of dithiol and a M_w of up to 101 000 g mol⁻¹ is reached. All polymers are quantitatively dehydrated by simple thermal treatment at a temperature ranging from 120 °C to 140 °C in the solid state, furnishing poly(oxazolidone-co-thioether) copolymers bearing exocyclic vinylene moieties and presenting a high thermal stability (T_deg10% up to 360 °C) and various glass transition temperatures. Post-polymerization modifications by thiol oxidation to sulfoxides or sulfones, or through S-alkylation of the thioether linkages, are realized to deliver unprecedented functional polyoxazolidones. Notably, the introduction of sulfonium groups enables the production of the first example of water-soluble polyoxazolidones. This work describes a simple platform to produce a large panel of functional polyoxazolidones that are not accessible by the current isocyanate-based methods, moreover under mild operating conditions by exploiting CO₂-based monomers.