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Light-induced shape-memory polymers

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 stimulus1,2,3. Shape-memory polymers have received increasing attention because of their scientific and technological significance4,5. 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 illumination6,7). Several papers have described light-induced changes in the shape of polymers8,9,10,11,12 and gels13,14,15, such as contraction8,9,10, bending11,12,13 or volume changes14,15. 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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Figure 1: Shape-memory effect of photoresponsive polymers.
Figure 2: UV absorption spectra.
Figure 3: Cyclic photomechanical experiment on a grafted polymer BHCA (10,2,1) under stress-controlled conditions.

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Acknowledgements

We thank the Bundesministerium für Bildung und Forschung for a BioFuture Award; H.J. is grateful for an AvH fellowship in 1999/2000.

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Correspondence to Andreas Lendlein.

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A.L., R.L. and H.J. have equity in, or have received fees from, mnemoScience, which holds certain patents in the area.

Supplementary information

Supplementary Table S1

Mechanical and thermal properties of the grafted polymer BHCA at 25 °C, permanent polymer networks BP and IPN polymer BP-SCAA. (DOC 42 kb)

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Lendlein, A., Jiang, H., Jünger, O. et al. Light-induced shape-memory polymers. Nature 434, 879–882 (2005). https://doi.org/10.1038/nature03496

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