Organic–inorganic nanocomposites for shape memory effects

Polyurethane (PU)-silica nanocomposites were synthesized by sol-gel reactions between the surface silanol groups of fumed silica and 3-aminopropyltriethoxysilane (APTES) terminated PU with a broad range of silica contents (1-5%) with two different molecular weights of PU. It was found that the silica particles that were incorporated into the polymer chains were well dispersed in the PU matrix and acted as multifunctional cross-links and reinforcing fillers; in addition, the silica particles augmented the initial and rubbery moduli, yield, and break strengths, as well as the glass transition temperature. Moreover, 98-99% shape fixity and shape recovery with minimum cyclic hysteresis were obtained with only 1% silica particle loading.