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A Bottom-Up Approach to Dual Shape-Memory Effects

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posted on 14.04.2015 by Juan Wang, Jin Li, Na Li, Xiaolong Guo, Liu He, Xuan Cao, Weiying Zhang, Rongxiang He, Zhiyong Qian, Yiping Cao, Yong Chen
This study demonstrates how to successfully bridge the gap between nanoscale shape-memory function and macroscale motion using a bottom-up approach. This was achieved by first fabricating a photoswitchable surface-molecular-imprinted layer-by-layer (LbL) film capable of memorizing the shape and size of template molecules when illuminated. This photoswitch was built on the fundamental supramolecular interaction between an α-cyclodextrin-modified template acting as a photosocket and an azobenzene-modified poly­(acrylic acid) photoplug. Corresponding patterns applied by cover-printing and wet photolithography were used to illustrate the stability of the binding sites; a simple and clean method was developed for removing the template–dye by UV irradiation. A functional fusion of nanoimprints and macroscopic materials was subsequently established by applying LbL coating technology to poly­(d,l-lactic acid) (PDLLA) modified to have a shape-memory effect. Macroscopic changes in shape were found to cause deformation of recognition cavities in terms of their shape and size, thereby enabling us to visualize the effect of the specific adsorption behavior toward template–dye on a patterned PDLLA sheet. The rapid swelling and surface erosion of PDLLA also revealed that an increase in the number of deposited layers can significantly affect the interfacial properties of both the substrate and LbL film. It is believed that such novel designs and methods should prove useful for the development of multifunctional biomaterials.