Synthesis of Renewable, Recyclable, Degradable Thermosets Endowed with Highly Branched Polymeric Structures and Reinforced with Carbon Fibers

Abstract

This paper demonstrates the molecular design of renewable polymer thermosets that are chemically recyclable yet degradable on demand. In this design, the thermosets comprise a limonene-based highly branched polymer, which has been synthesized via the regioselective thiol−ene reaction between natural limonene and multifunctional thiol, and a Meldrum's acid derivative for the click/declick reaction of thiol groups that are deliberately positioned on the outer surface of the branched polymer. Thus, the accessible thiols expedite the covalent bond exchange reaction and enable the formation of a network and bulk recycling of the entire network; the labile cross-linkers enable molecular degradation or repurposing of the materials under benign conditions. The thermosets can be also reinforced with the addition of carbon fibers. Thus, reversible deformation or self-lamination of the resultant carbon composites, which are degradable and recyclable, was achieved owing to the thermosets, which act as a matrix or binder. We envision that the renewable materials presented here would be advanced by introducing diverse biomolecules or reversible chemistry to develop disposable bio-based platforms that can be further upcycled at the end of their lifecycles.

Renewable Photopolymers: Transformation of Biomass Resources into Value-Added Products Under Light

“…For example, limonene was reacted with PETMP with an off stoichiometric molar ratio of functional groups to form a highly branched polymer via thiol−ene photopolymerization (Figure 9). 212 The resulting polymer was generated with most of the unreacted thiol groups mainly positioned on the outer surface. The unreacted thiol groups were intermolecularly cross-linked in the presence of small amounts of the Meldrum's acid.…”

“…Thiol–ene photopolymerization of d -limonene (1) and tetra-functional thiol (2, PETMP) to give a highly branched prepolymer (3) and the resultant renewable thermoset (5) from (3) after thermal treatment of (3) in the presence of cross-linker (4). Reproduced from ref . Copyright 2023 American Chemical Society.…”

Branched Polymers: Synthesis and Application

“…Branched polymers have different structures, such as graft polymers, − star polymers, − and highly branched polymers. − Due to structural differences, they exhibit different chemical properties even though they have the same chemical composition. Branched polymers are synthesized via diverse methods, which can be classified into step-growth polymerization, e.g., condensation–polymerization and addition polymerization, and chain-growth polymerization, e.g., radical polymerization, cationic polymerization, and anionic polymerization.…”