1. GKSS Research Center Geesthacht GmbH, Institute of Chemistry, Kantstrae 55, D-14513 Teltow, Germany
2. Institute for Technology and Development of Medical Devices, RWTH Aachen, Pauwelsstrae 30, and
3. mnemoScience GmbH, Pauwelsstrae 19, D-52074 Aachen, Germany
4. Department of Chemical Engineering, Massachusetts Institute of Technology, 45 Carleton Street, Cambridge, Massachusetts 02139, USA
5. Present address: Prof.-Staudinger-Strasse, D-65451 Kelsterbach, Germany

Correspondence to: Andreas Lendlein^1,2 Correspondence and requests for materials should be addressed to A.L. (Email: Lendlein@gkss.de).

Abstract

Materials are said to show a shape-memory effect if they can be deformed and fixed into a temporary shape, and recover their original, permanent shape only on exposure to an external stimulus^{1, 2, 3}. Shape-memory polymers have received increasing attention because of their scientific and technological significance^{4, 5}. In principle, a thermally induced shape-memory effect can be activated by an increase in temperature (also obtained by heating on exposure to an electrical current⁶ or light illumination^{6, 7}). Several papers have described light-induced changes in the shape of polymers^{8, 9, 10, 11, 12} and gels^{13, 14, 15}, such as contraction^{8, 9, 10}, bending^{11, 12, 13} or volume changes^{14, 15}. Here we report that polymers containing cinnamic groups can be deformed and fixed into pre-determined shapes—such as (but not exclusively) elongated films and tubes, arches or spirals—by ultraviolet light illumination. These new shapes are stable for long time periods, even when heated to 50 °C, and they can recover their original shape at ambient temperatures when exposed to ultraviolet light of a different wavelength. The ability of polymers to form different pre-determined temporary shapes and subsequently recover their original shape at ambient temperatures by remote light activation could lead to a variety of potential medical and other applications.

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