Multilayered shape-memory composites composed of multiwalled carbon nanotube (MWCNT)-filled thermoplastic polyurethane (TPU) (denoted as cTPU) and polycaprolactone (PCL) were prepared through layer-multiplying coextrusion. The phase interfaces and conductive pathways in the multilayered structure which can be tailored by layer-multiplying endowed the materials with tunable thermo- and electro-responsive shape-memory effects (TSME and ESME). Compared with the conventional blending composite having the same compositions, the cTPU/PCL multilayered system with high phase continuity and abundantly continuous interfaces exhibited better TSME, which could be further enhanced with increasing the layer number. It was revealed that the strain energy stored in cTPU layers would be balanced by adjacent PCL layers via interfacial shearing effect so that each domain could endow the maximum contribution to the shape-memory performance. Besides, the confined layer space allowed for a more compact connection between the MWCNTs than in the blending composite, while the original conductive network formed in cTPU tended to be gradually broken up during layer multiplying. Moreover, an excessive conductivity may induce local overheating and even the melting of permanent domains, leading to undesired deformation. Accordingly, the multilayered composite with a proper layer number which exhibited suitable conductivity and efficient TSME achieved balanced ESME with quick recovery speed, excellent recovery ratio, and good appearance retention. This work opened an avenue in preparing outstanding shape-memory materials with both thermal and electrical actuations, which showed great potential in applications of sensors, actuators, self-deployable devices, and so forth.

中文翻译：

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MWCNTs分布受限的热塑性聚氨酯/聚己内酯多层复合材料的制造，以实现可调节的热响应和电响应形状记忆性能

通过层合共挤出制备了由多壁碳纳米管（MWCNT）填充的热塑性聚氨酯（TPU）（称为cTPU）和聚己内酯（PCL）组成的多层形状记忆复合材料。多层结构中的相界面和导电路径可以通过层乘来定制，从而赋予材料可调节的热响应和电响应形状记忆效应（TSME和ESME）。与具有相同组成的常规共混复合材料相比，具有高相连续性和丰富连续界面的cTPU / PCL多层体系具有更好的TSME，可通过增加层数进一步提高。结果表明，存储在cTPU层中的应变能将通过界面剪切作用被相邻的PCL层平衡，从而使每个畴对形状记忆性能的贡献最大。此外，与混合复合材料相比，有限的层间空间使MWCNT之间的连接更加紧凑，而在cTPU中形成的原始导电网络往往在层倍增过程中逐渐破裂。此外，过度的导电性可能引起局部过热，甚至导致永久性区域的熔化，从而导致不希望的变形。因此，具有适当层数的多层复合材料表现出合适的电导率和有效的TSME，从而获得了平衡的ESME，具有快速的恢复速度，优异的恢复率和良好的外观保持性。