Tunable shape memory properties of rigid–flexible epoxy networks

A series of regular and tunable rigid–flexible crosslinking networks have been prepared to investigate shape memory effects. The tunable rigid–flexible epoxy resins (TRFEPs) were synthesized by ultraviolet light thiol–ene click chemistry. The FTIR and ¹H NMR measurements indicated that TRFEPs were successfully synthesized. The thermal, thermomechanical, mechanical, and shape memory properties of all regular crosslinking networks were systematically investigated by DSC, DMA, tensile test, and quantitative shape memory evaluation method, respectively. It was found that with the flexibility of the crosslinking networks increasing, T _gDSC, T _gDMA, E′ (25 °C), shape recovery rate, and tensile stress decreased and elongation at break increased. Besides, DMA measurements showed that the regular network had relatively narrow glass transition zone. The tunable rigid–flexible crosslinking networks exhibited a ductile plastic fracture feature with the occurrence of yielding phenomenon and had relatively high tensile strength (20–44 MPa). Quantitative shape memory evaluation disclosed that the regular crosslinking networks exhibited excellent shape memory performance with high shape memory fixity (>97 %) and shape memory recovery (>99 %). Especially, it was discovered that the regularity of network was the primary effect factor and the flexibility was the subordinate effect factor on the shape recovery rate. Excellent shape memory properties and great mechanical properties make the materials good candidates for space deployable structure materials and wide applications in other important fields.