Meng Yuan, Jiang Jisu, Anthamatten Mitchell
Department of Chemical Engineering, University of Rochester, 250 Gavett Hall, Rochester, New York 14627, United States.
ACS Macro Lett. 2015 Jan 20;4(1):115-118. doi: 10.1021/mz500773v. Epub 2015 Jan 10.
We demonstrate a single-phase, two-way shape actuator that, in the absence of an external load, elongates upon cooling and reversibly contracts upon heating. In a simple and straightforward process, a partially cross-linked, semicrystalline poly(ε-caprolactone) (PCL) network is melted, stretched to several hundred percent strain, and further cross-linked. Upon removal of the applied load, the elastic double network adopts a "state-of-ease" that retains part of its former strain. When cooled, internal stress-induced crystallization causes further elongation of configurationally biased chains. When heated, crystallites melt, and the sample returns to its equilibrium state-of-ease. Under optimized conditions, reversible actuation >15% strain can be reproducibly achieved, and samples can be cycled multiple times with highly uniform actuation with no observable creep. The mechanism behind such actuation was further confirmed via calorimetry and X-ray scattering.
我们展示了一种单相双向形状致动器，在没有外部负载的情况下，它在冷却时伸长，加热时可逆收缩。通过一个简单直接的过程，将部分交联的半结晶聚（ε-己内酯）（PCL）网络熔化，拉伸至几百%的应变，然后进一步交联。去除施加的负载后，弹性双网络采用一种“松弛状态”，保留其先前应变的一部分。冷却时，内应力诱导的结晶导致构型偏向链进一步伸长。加热时，微晶熔化，样品回到其平衡松弛状态。在优化条件下，可重复实现大于15%应变的可逆致动，并且样品可以多次循环，具有高度均匀的致动且无明显蠕变。通过量热法和X射线散射进一步证实了这种致动背后的机制。
