一张塑料薄片放置到60摄氏度热水里，短短几秒钟，塑料薄片收缩变形成了一只“千纸鹤”。
这是浙江大学化学工程与生物工程学院谢涛教授课题组最新研发的一种新型的形状记忆塑料，它能多次“植入”复杂形状记忆，遇热即展现多样形变。相关论文于北京时间9日凌晨发表在《科学》杂志子刊《科学进展》上。
形状记忆塑料是一类能够固定临时形状并且在外界刺激下回复到初始形状的智能材料，在柔性电子、生物医学和航空航天等领域展示出越来越广的应用前景。
谢涛介绍，研究团队在设计新型形状记忆材料的过程中，加入了一种可交换共价键，重组分子间的连接关系。这相当于很多分子手拉手跳一支“集体舞”，当处于较高的温度时，分子之间相互“换手”，找到了新伙伴、新“队形”，产生永久记忆。当处于较低温度环境下，材料即使被折叠成其他形状，产生弹性形变，分子之间也不会“放手”，遇热还是能恢复原有形状。
论文第一作者、浙江大学化学工程与生物工程学院副教授赵骞说，正是这种“换手”的特性，让新型形状记忆塑料有不断被植入复杂形状记忆的性能，新形状还能不断叠加其中。利用这种效应，可以制备现有加工方法难以实现的复杂形状。
研究人员认为，这一新型材料具有广阔实用价值和应用前景，研究人员期待这一材料能早日用于诸如生物医疗或柔性电子等高附加值应用领域。“比如心脏支架，我们希望它在到达植入‘目的地’以后，可以舒展成为一个复杂三维形状。”谢涛说。
《科学进展》杂志评审专家认为，该项研究是形状记忆聚合物领域的重要突破，为形状记忆材料的设计与加工提供了全新指导。（新华社 朱涵）
摘要速递：
Shape memory polymer network with thermally distinct elasticity and plasticity
Science Advances
08 Jan 2016
DOI: 10.1126/sciadv.1501297
Stimuli-responsive materials with sophisticated yet controllable shape-changing behaviors are highly desirable for real-world device applications. Among various shape-changing materials, the elastic nature of shape memory polymers allows fixation of temporary shapes that can recover on demand, whereas polymers with exchangeable bonds can undergo permanent shape change via plasticity. We integrate the elasticity and plasticity into a single polymer network. Rational molecular design allows these two opposite behaviors to be realized at different temperature ranges without any overlap. By exploring the cumulative nature of the plasticity, we demonstrate easy manipulation of highly complex shapes that is otherwise extremely challenging. The dynamic shape-changing behavior paves a new way for fabricating geometrically complex multifunctional devices.
Design of network with thermally distinct elasticity and plasticity. (A) Schematics of the physical molecular principle. Black dots represent permanent crosslinking points; green and blue colors represent the activated and nonactivated states of the reversible bonds, respectively; and red and dark gray lines represent the activated and nonactivated states of the chain segments, respectively. (B) Precursor monomers for the network synthesis.
Shape manipulation via thermally distinct elasticity and plasticity. (A) Smart origami structures. (B) Smart kirigami structure. Scale bars, 10 mm.
————引自“高分子科学前沿”
