Reconfiguration and shape memory triggered by heat and light of carbon nanotube-polyurethane vitrimer composites

Thermoset shape-memory polymers (SMPs) are widely applied because of their superiority in maintaining permanent shapes. However, the inferiority of this material is also conspicuous, namely the loss of reprocessing ability owing to the chemically crosslinked structure. Fortunately, a new class of SMPs, known as "vitrimers," was discovered, which can be reshaped or reprocessed via topological rearrangement due to the existence of dynamic covalent bonds. Thus, this new thermoset SMP could become a novel solution. In this paper, carbon nanotube-polyurethane vitrimer (CNT-PUV) composites have been prepared, which possess the capability of thermally induced shape memory based on entropy changes and thermal reconfiguration based on transcarbamoylation reactions of carbamate bonds. In addition, the introduction of CNTs endows them with properties of near-infrared (NIR) triggered shape memory and reconfiguration due to the photothermal conversion effect of CNTs. Besides, due to the character of the NIR laser, step-by-step shape recovery of CNT-PUVs is realized from predefined temporary shapes to a permanent shape. (C) 2017 Wiley Periodicals, Inc.