Shape‐Memory Semicrystalline Polymeric Materials Based on Various Rubbers

Abstract

AbstractA simple strategy is presented for the fabrication of shape‐memory materials containing commercial rubbers including natural rubber, cis‐polybutadiene, and styrene‐butadiene rubber. Dissolution of the rubbers in n‐octadecyl acrylate (C18A) monomer followed by UV polymerization at 30 °C leads to the formation of interconnected interpenetrating polymer networks (c‐IPNs) possessing crystalline domains. They exhibit melting (Tm) and crystallization temperatures (Tcry) between 45–50 and 35–40 °C, respectively, that can be tuned by the amount and the type of the rubbers. All c‐IPNs exhibit a significant temperature sensitivity in their viscoelastic and mechanical properties when the temperature is changed between below and above Tm and Tcry. The morphology of c‐IPNs consists of amorphous nanoparticles of around 64 nm diameter composed of interconnected noncrystalline poly(C18A) (PC18A) and rubber networks, surrounded by crystalline PC18A segments. c‐IPNs exhibit tunable mechanical properties, for example, their Young's modulus and toughness can be varied between 8.3–73 MPa, and 1.9–23 MJ·m−3, respectively, by changing the amount and type of the rubber. Because of the coexistence of chemical cross‐links and crystalline domains acting as the netpoints and switching segments, respectively, c‐IPNs exhibit an efficient shape‐memory function as demonstrated by their potential application as a robotic gripper.