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

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 1 H–NMR spectrum. Then, this small molecule is utilized to prepare oligomer, linear polymer and the corresponding crosslinked polymer (denoted as P 2 ) by using thiol-ene and thiol-oxidation reactions. The polymer P 2 can form brown film on a glass substrate and can be easily put off from the substrate. Mechanical properties of P 2 show that tensile strength value is about 6 MPa, with elongation at break of around 300%. Glass transition temperature (Tg) of P 2 is −2.76 °C, meaning that P 2 is at rubber state. There are hydroxyl groups in the prepared linear polymer, which further reacts with 1,6-hexanediisocyanate (HDI) to form polyurethane P 4 with crosslinked structures. Compared with P 2 , the polyurethane P 4 forms yellow film on a glass substrate. But the film of P 4 is not so flexible as that of P 2 , presumably because of relatively higher Tg (5.85 °C) of P 4 than P 2 . Due to the existence of dynamic disulfide bonds as well as hydrogen bonds in both P 2 and P 4 , these thermoset resins show repeatable self-healing behavior stimulated by UV irradiation. Furthermore, the polyurethane P 4 exhibits ultrahigh temperature resistance performance, with Td 5  = 375 °C and Td 10  = 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.