Lendlein Andreas, Jiang Hongyan, Jünger Oliver, Langer Robert
GKSS Research Center Geesthacht GmbH, Institute of Chemistry, Kantstrasse 55, D-14513 Teltow, Germany.
Nature. 2005 Apr 14;434(7035):879-82. doi: 10.1038/nature03496.
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. Shape-memory polymers have received increasing attention because of their scientific and technological significance. 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 current or light illumination). Several papers have described light-induced changes in the shape of polymers and gels, such as contraction, bending or volume changes. 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 degrees 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.
如果材料能够发生变形并固定成临时形状，且仅在受到外部刺激时才恢复其原始的永久形状，那么就称这些材料具有形状记忆效应。形状记忆聚合物因其科学技术意义而受到越来越多的关注。原则上，热致形状记忆效应可通过温度升高来激活（也可通过暴露于电流或光照下加热获得）。几篇论文描述了光致聚合物和凝胶形状的变化，如收缩、弯曲或体积变化。在此我们报告，含肉桂酸基团的聚合物在紫外线照射下能够发生变形并固定成预定形状，例如（但不限于）细长薄膜和管子、拱形或螺旋形。这些新形状即使加热到50摄氏度也能长时间保持稳定，并且当暴露于不同波长的紫外线时，它们在环境温度下能够恢复其原始形状。聚合物通过远程光激活在环境温度下形成不同预定临时形状并随后恢复其原始形状的能力可能会带来各种潜在的医学及其他应用。
