Development of liquid crystalline polyurethane composites with stage-responsive shape memory effects

Abstract

Shape memory polymers (SMPs) have received significant attention from scientists in recent years. This paper presents a simple route to design light-thermo stage-responsive SMPs. A novel series of liquid crystalline shape memory polymer composites (coded as PSMPU-Azom) exhibiting stage-responsive shape memory properties were successfully prepared by incorporating 4-(4-oxyalkyl chain carbonyl) azodibenzoic acid (Azo11) into the PCL-based SMPs (PSMPU). The effect of Azo11 on the structure, morphology, and shape memory properties was carefully investigated. The results demonstrate that the incorporated Azo11 promotes the crystallizability of PSMPU. The obtained PSMPU-Azom composites form a two-phase structure comprising the PSMPU phase and Azo11 phase, while the polyurethane matrix even shows hard–soft phase separation structure. Therefore, the PSMPU-Azom composites retain the intrinsic liquid crystalline properties of Azo11. Moreover, the PSMPU-Azom composites have stage-responsive shape memory properties and hence, demonstrate unique features such as independent UV light-responsive deformation and thermal-responsive shape recovery. These composites display a rare combination of light- and thermal-responsiveness, which not only allows instantaneous shape-deformation under UV irradiation, but can also be temporarily fixed to a particular shape on stopping the UV irradiation at room temperature. The composites have good potential applications in smart optical devices, smart electronic devices, smart sensors, and robotic fingers.