Organic–inorganic nanocomposites for shape memory effects

Abstract

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.

Thermoset shape memory polymers and their composites

“…SMPUs crosslinked/reinforced by inorganic nanoparticles, such as CNFs (Lu et al, 2014c), CNTs (Cho et al, 2005; Jin et al, 2011; Jung et al, 2010; Lee and Yu, 2011; Mahapatra et al, 2014; Rana et al, 2013), 3-aminopropyl triethoxysilane (KH550) (Xu et al, 2006), polyhedral oligomeric silsesquioxane (POSS) (Bothe et al, 2012; Jung et al, 2006), hydrophilic silica (Bae et al, 2011; Jang et al, 2009; Kang et al, 2012), dimethylsiloxane (Alexandru et al, 2011), montmorillonite (Chung et al, 2011), graphite oxide (Choi et al, 2012), and Fe 3 O 4 (Kalita and Karak, 2013) have been widely studied in recent years. Among these studies, a multi-layered CNF nanopaper–enabled SMPU nanocomposite was investigated in view of the synergistic effect of self-assembled carbon nanopaper and a multi-layered interface on shape memory nanocomposites for high-speed electrical actuation.…”

Synthesis and properties of shape memory graphene oxide/polyurethane chemical hybrids

“…where N is the number of subchains per volume, T is the absolute temperature and k is the Boltzmann constant. Even in a non‐reactive system, addition of inorganic particles to a polymer generally augments the rubbery and glassy moduli due to the filler effect . Therefore, the decrease in modulus with GO is an indication of a decrease in the number of crosslinking sites.…”

Actuation design for high‐performance shape memory polyurethanes

“…The T g of SMPU can be controlled by the structure–property relationship, by nanocomposite formation of the SMPU, or by external methods such as moisture content . An intensive phase mixing is needed to endow a sharp transition and high temperature sensitivity.…”