Heat-Resistant Shape\nMemory Fully Biobased Epoxy Resins\nwith High Storage Modulus and Recycle Performance

Combining high heat resistance and\ngreen sustainability\nis a great\nchallenge in developing shape memory epoxy resins. Herein, starting\nfrom synthesizing a fully biobased trifunctional epoxy compound (ER),\na kind of fully biobased epoxy resin system (EFT<i>x</i>, where <i>x</i> is the molar ratio of carboxyl to epoxy\ngroups) is developed. The effects of <i>x</i> on the structure\nand properties of EFT<i>x</i> resins were systematically\ninvestigated. Results show that cured EFT<i>x</i> resins\nhave excellent heat resistance, high mechanical properties, shape\nmemory performance, and recycle ability. As <i>x</i> of\nEFT<i>x</i> resin increases, the glass transition temperature\n(<i>T</i><sub>g</sub>) and initial thermal decomposition\ntemperature (<i>T</i><sub>di</sub>) decrease while both\nself-healing efficiency and remolding efficiency increase. The <i>T</i><sub>g</sub> and storage modulus of each EFT<i>x</i> resin are much higher than those of reported fully biobased shape\nmemory epoxy resins. Among EFT<i>x</i> resins, EFT<sub>1.0</sub> resin shows the best-integrated performance; specifically, its <i>T</i><sub>g</sub>, <i>T</i><sub>di</sub>, tensile\nstrength, and self-healing efficiency are as high as 156 °C,\n293 °C, 40.99 MPa, and 90.5%, respectively, meanwhile it also\nhas outstanding shape memory property reflected by the high shape\nfixation ratio (<i>R</i><sub>f</sub> = 100%) and shape recovery\nratio (<i>R</i><sub>r</sub> = 97.8%) under the bend-recovery\nexperiments as well as high <i>R</i><sub>f</sub> (93.2%)\nand <i>R</i><sub>r</sub> (66.1%) after four tensile shape\nmemory cycles. The outstanding integrated performance of EFT<i>x</i> resins is attributed to their unique structures that combine\nrigid stilbene structure, furan ring, and abundant ester bonds.