基于折叠式电场的聚合物基可拉伸导体的制备及导电特性研究

Development of stretchable conductors is a new direction for conducting materials that has attracted extensive interests, and conductive polymer-based composites (CPCs) are a promising approach to the stretchable conductors. To overcome high filler contents and low stretchabilities of CPCs, electrical fields with folded electrical-field lines were devised to tailor the distribution of conductive fillers as well as to form a stretchable buckling conductive network, and thus a highly stretchable CPC was fabricated. Firstly, two types of fields with folded electrical-field lines, accordion-like and anchor-like respectively, were prepared by regulating the relative position, distribution and size of electrodes, and were then simulated based on finite element analysis. Subsequently, the two fields, respectively, were divided into small units of quasi-uniform field, in which the alignment dynamics of carbon nanotubes (CNTs) was modeled in terms of a dielectrophoretic theory. Accordingly, the CNTs were induced to align along the electrical-field lines in polydimethylsiloxane (PDMS) by controlling the process, thereby to form a stretchable buckling conductive network. Finally, microscopies, Raman spectroscopy and X-ray diffraction were performed to characterize the structure of the CNTs conductive network, based on which the electrical conductivity of the CPCs was investigated as a function of stretchability. The folded electrical field favors the formation of stretchable conductive network, the reduction of CNTs loading level, the retention of high elasticity for PDMS, and the enhancement of interactions between CNTs by CNTs coarsening effects, all of which conduce to the preparation of conductors with high stretchability. This project provides theoretical basis as well as a novel pathway for the development of buckling conductive networks and the fabrication of stretchable conductors.

可拉伸导体是导电材料的发展新方向。聚合物基导电复合材料是制备可拉伸导体的一种重要途径。为克服导电复合材料高填充量和低拉伸倍率的问题，本项目设计具有折叠电场线的电场来调控填料的分布，形成折叠导电网络以制备可拉伸导体。首先控制电极相对位置、分布和尺寸等制备手风琴式和锚式两种折叠电场，并基于有限元模拟该电场；然后采用“化整为零”的方式将两种电场分别分割为准均匀电场的小单元，基于双向电泳理论模拟碳纳米管在两种电场下的取向动力学；再控制工艺以诱导碳纳米管在聚二甲基硅氧烷中沿电场方向排列，形成折叠的导电网络；最后利用显微术、拉曼光谱及X射线衍射等表征导电网络的结构，研究复合材料的电学可拉伸性。折叠电场有助于形成可拉伸的导电网络,降低碳纳米管用量,保持聚硅氧烷的高弹性，并产生粗化效应增强碳纳米管间相互作用；这些均有益于高倍率拉伸导体的制备。本项目为设计折叠导电网络与制备可拉伸导体提供了理论基础和新途径。

可拉伸导体是指材料在受到较大的应变时仍保持良好电学性能的一种新型智能电子材料，其在可穿戴电子器件、电子皮肤、智能织物等新型智能材料领域有着非常重要的应用。聚合物基导电复合材料是一种制备可拉伸导体的重要途径。在聚合物基体中形成多层次折叠的可拉伸导电网络结构，增强其结构可拉伸性是一种高效且应用较多的方法，也称为结构可拉伸导体。然而，目前的聚合物基可拉伸导体存在填充量高且导电网络的可拉伸性低等问题，严重影响了其电学可拉伸特性。本项目设计并制备具有折叠电场线的电场来调控填料的分布，形成折叠导电网络以制备可拉伸导体。首先采用Ansoft软件模拟了电极数量、距离及形貌对电场分布的影响规律，根据模拟结果，选择铜制材料为电极设计制备了手风琴式和锚式两种具有折叠电场线的电场；然后利用该电场诱导碳纳米管（CNTs）在硅橡胶（PDMS）中的分布，制备可拉伸导体，研究了CNTs含量、电场强度、电场类型（交流或直流）、交流电场频率、取向时间等工艺对材料制备的影响规律。结果发现，具有折叠导电网络的复合材料的CNTs用量低，且电阻相对变化远低于填料随机分布的复合材料，说明其折叠的导电网络有利于改善电学可拉伸性；同时手风琴式电场制备的材料效率高于锚式电场。最后揭示了柔性导体电学性能随着应变的变化规律，并将该规律进一步拓展，开发了混杂填料法和溶胀渗透法等制备柔性力敏材料的方法。目前已经发表学术论文9篇，其中英文SCI6篇，中文EI2篇，中文核心期刊1篇；申请专利9个，授权2个；研究成果获得湖北省科技进步一等奖一项和湖北省技术发明奖三等奖一项。