Organic–inorganic chemical hybrids having shape memory effect

Vinyltrimethoxysilane (VTMS)-modified silica particles were incorporated into the chain of amorphous polyurethane (PU) by covalent bonds, to synthesize an organic–inorganic hybrid material with an extremely long relaxation time. At 1% silica, the PU–silica chemical hybrids gave over 99% shape fixity and shape recovery with <2% hysteresis during the four thermomechanical cycles. As silica content increases (2, 3%) shape memory performance slightly decreased with repeated cycles. Results were favorably compared with PUs cross-linked by hydroxyl ethylacrylate (HEA) and VTMS, and physical blends with silica particles. The results were interpreted based on the triple effects of silica particles as multifunctional cross-linkers, reinforcing fillers, and relaxation retarders of the polymer chains during loading and unloading.