Heat-Resistant Shape Memory Fully Biobased Epoxy Resins with High Storage Modulus and Recycle Performance

Combining high heat resistance and green sustainability is a great challenge in developing shape memory epoxy resins. Herein, starting from synthesizing a fully biobased trifunctional epoxy compound (ER), a kind of fully biobased epoxy resin system (EFTx, where x is the molar ratio of carboxyl to epoxy groups) is developed. The effects of x on the structure and properties of EFTx resins were systematically investigated. Results show that cured EFTx resins have excellent heat resistance, high mechanical properties, shape memory performance, and recycle ability. As x of EFTx resin increases, the glass transition temperature (Tg) and initial thermal decomposition temperature (Tdi) decrease while both self-healing efficiency and remolding efficiency increase. The Tg and storage modulus of each EFTx resin are much higher than those of reported fully biobased shape memory epoxy resins. Among EFTx resins, EFT1.0 resin shows the best-integrated performance; specifically, its Tg, Tdi, tensile strength, and self-healing efficiency are as high as 156 °C, 293 °C, 40.99 MPa, and 90.5%, respectively, meanwhile it also has outstanding shape memory property reflected by the high shape fixation ratio (Rf = 100%) and shape recovery ratio (Rr = 97.8%) under the bend-recovery experiments as well as high Rf (93.2%) and Rr (66.1%) after four tensile shape memory cycles. The outstanding integrated performance of EFTx resins is attributed to their unique structures that combine rigid stilbene structure, furan ring, and abundant ester bonds.