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 (T g) and initial thermal decomposition temperature (T di) decrease while both self-healing efficiency and remolding efficiency increase. The T g 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 T g, T di, 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 (R f = 100%) and shape recovery ratio (R r = 97.8%) under the bend-recovery experiments as well as high R f (93.2%) and R r (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.