Exploiting Microphase-Separated Morphologies of Side-Chain Liquid Crystalline Polymer Networks for Triple Shape Memory Properties

We report a new strategy to achieve triple shape memory properties by using side-chain liquid crystalline (SCLC) type random terpolymer networks (XL- TP-n), where n is the length of flexible methylene spacer (n = 5, 10, and 15) to link backbone and mesogen. A lower glass transition temperature (Tg = Tlow) and a higher liquid crystalline clearing temperature (Tcl = Thigh) of XL-TP-n serve as molecular switches to trigger a shape memory effect (SME). Two different triple shape creation procedures (TSCPs), thermomechanical treatments to obtain temporary shapes prior to the proceeding recovery step, are used to investigate the triple shape memory behavior of XL-TP-n. The discrete Tg and Tcl as well as unique microphase-separated morphologies (backbone-rich and mesogen-rich domains) within smectic layers of XL-TP-n enables triple shape memory properties. Motional decoupling between backbone-rich and mesogen-rich domains is also critical to determine the resulting macroscopic shape memory properties. Our strategy for obtaining triple shape memory properties will pave the way for exploiting a broad range of SCLC polymers to develop a new class of actively moving polymers.