Renewable eugenol-based functional polymers with self-healing and high temperature resistance properties

Abstract

A novel small molecule 1,3-bis(eugenyl) glycerol diether is synthesized from renewable eugenol and epichlorohydrin in 60% total yield, and its structure is confirmed by ¹H–NMR spectrum. Then, this small molecule is utilized to prepare oligomer, linear polymer and the corresponding crosslinked polymer (denoted as P₂ ) by using thiol-ene and thiol-oxidation reactions. The polymer P₂ can form brown film on a glass substrate and can be easily put off from the substrate. Mechanical properties of P₂ show that tensile strength value is about 6 MPa, with elongation at break of around 300%. Glass transition temperature (Tg) of P₂ is −2.76 °C, meaning that P₂ is at rubber state. There are hydroxyl groups in the prepared linear polymer, which further reacts with 1,6-hexanediisocyanate (HDI) to form polyurethane P₄ with crosslinked structures. Compared with P₂ , the polyurethane P₄ forms yellow film on a glass substrate. But the film of P₄ is not so flexible as that of P₂ , presumably because of relatively higher Tg (5.85 °C) of P₄ than P₂ . Due to the existence of dynamic disulfide bonds as well as hydrogen bonds in both P₂ and P₄ , these thermoset resins show repeatable self-healing behavior stimulated by UV irradiation. Furthermore, the polyurethane P₄ exhibits ultrahigh temperature resistance performance, with Td₅ = 375 °C and Td₁₀ = 1000 °C according to TGA curve. This work is expected to expand research and potential applications of the renewable resource eugenol in preparation of smart materials.

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