Programmable Shape Change in Semicrystalline Liquid Crystal Elastomers
Programmable Shape Change in Semicrystalline Liquid Crystal Elastomers
复制标题
半结晶液晶弹性体的可编程形状变化
DOI：
10.1021/acsami.2c07533
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发表时间：
2022
影响因子：
9.5
通讯作者：
Ware, Taylor H.
中科院分区：
文献类型：
--
作者：
Javed, Mahjabeen;Corazao, Tyler;Saed, Mohand O.;Ambulo, Cedric P.;Li, Yuzhan;Kessler, Michael R.;Ware, Taylor H.
液晶弹性体（LCEs）是一种刺激响应材料，能够在环境刺激下发生可逆和可编程的形状变化。尽管这些材料具有高响应性，但这些致动材料所表现出的适度弹性模量和阻塞应力在某些工程应用中可能受到限制。在这里，我们设计了一种半结晶LCE，其中半结晶性与轻度交联的液晶网络相结合，产生了坚韧和高响应性的材料。定向自组装可以通过半晶LCE的厚度来编制导向器轮廓。简而言之，我们使用液晶单体相的排列来绘制半晶聚合物网络的各向异性。半晶-液晶和液晶-各向同性相变温度都提供了可控的形状转变。平行于向列指向器的平面排列样品的归一化尺寸从室温下的1减小到250℃时的0.42。半晶性质的引入也提高了半晶LCE的力学性能。半晶LCEs在室温下的存储模量为390 MPa，单畴样品在25至50℃加热时能够产生2.7 MPa的收缩应力，远低于向列向各向同性转变温度。这种材料强大的机械性能与高驱动应变相结合，可以用于软机器人和执行器等能够完成重要工作的应用。
Liquid crystal elastomers (LCEs) are stimuli-responsive materials capable of reversible and programmable shape change in response to an environmental stimulus. Despite the highly responsive nature of these materials, the modest elastic modulus and blocking stress exhibited by these actuating materials can be limiting in some engineering applications. Here, we engineer a semicrystalline LCE, where the incorporation of semicrystallinity in a lightly cross-linked liquid crystalline network yields tough and highly responsive materials. Directed self-assembly can be employed to program director profiles through the thickness of the semicrystalline LCE. In short, we use the alignment of a liquid crystal monomer phase to pattern the anisotropy of a semicrystalline polymer network. Both the semicrystalline-liquid crystalline and liquid crystalline–isotropic phase transition temperatures provide controllable shape transformations. A planarly aligned sample’s normalized dimension parallel to the nematic director decreases from 1 at room temperature to 0.42 at 250 °C. The introduction of the semicrystalline nature also enhances the mechanical properties exhibited by the semicrystalline LCE. Semicrystalline LCEs have a storage modulus of 390 MPa at room temperature, and monodomain samples are capable of generating a contractile stress of 2.7 MPa on heating from 25 to 50 °C, far below the nematic to isotropic transition temperature. The robust mechanical properties of this material combined with the high actuation strain can be leveraged for applications such as soft robotics and actuators capable of doing significant work.