聚吡咯纳米管复合水凝胶三维导电骨架的构筑及演变对其应变传感性能影响

Conducting polymer based composite hydrogels, which exhibit both ionic conductivity and electronic conductivity, have shown attractive application potentials as a kind of flexible stain sensitivity material. However, at present, problems are still remained with conducting polymer based hydrogels considering that they will be used in a strain sensor, such as lower linearity of resistivity–strain curve in a wider strain range, poor sensing stability, especially small strain-sensing gauge factor for anti-freezing and non-drying hydrogels. This project aims to construct a composite conductive hydrogel containing continuous electrons and ions conducting pathways on a larger scale provided by 3D porous structure composed of polypyrrole nanotubes, and polymer networks with covalent bond and dynamic ionic cross-linking points as the matrix. With this design, it was supposed that the highly conducting polypyrrole nanotubes as well as multiple non-covalent bonding interactions between polypyrrole and the matrix polymer will facilitate to form well connected conducting pathways, which can also deform and reconstruct effectively adapting to the strain of the hydrogel. The relatively stable doping state of polypyrrole nanotubes makes it possible to tune the medium composition of the composite hydrogels with both acidic form electrolytes and cryoprotectants, in order to simultaneously obtain anti-freezing, non-drying hydrogels and improve their strain-sensing gauge factor. Moreover, phase morphology of the composites at different strain levels will be studied in order to illustrate the effects of the 3D conducting framework evolution on the strain-sensing performance of the composite hydrogels. The progress of this project will provide important reference for the development of high-performance flexible electronic materials based on conducting polymers.

导电聚合物基水凝胶兼具电子、离子双重传导机制，作为柔性应变传感材料已表现出可观的应用潜力。目前导电聚合物基水凝胶用于应变传感时，仍面临着电阻-应变关系线性范围窄、响应稳定性差，尤其是其电阻-应变灵敏系数与水凝胶对环境温度的耐受性难以兼顾等困境。本项目拟以聚吡咯(PPy)纳米管三维多孔结构为导电骨架，以共价键和动态离子交联的高分子网络为基体，构建一种具有大尺度连续电子、离子双导电网络的复合水凝胶。利用PPy纳米管的高导电性、大长径比，及其与基体间的多重非共价作用，促使应变产生和回复过程中导电网络有效地变形且易于重构。基于PPy纳米管的掺杂导电行为，采用路易斯酸类电解质协同抗冻剂调节水凝胶的介质组成，以兼顾其电阻-应变关系的灵敏性和温度耐受性。结合对不同应变水平下复合体系的相形态探讨，揭示三维导电骨架随应变的演变对复合体系电阻-应变关系的影响，为获得高性能的导电聚合物基柔性电子材料提供参考。

导电高分子水凝胶普遍存在着合成工序复杂、应变传感灵敏度低等缺点，本项目提出将吡咯化学氧化聚合得到高亲水性聚吡咯(PPy)纳米管三维骨架与交联水溶性高分子网络有效结合，构建出其导电网络能够随着宏观变形发生联动的水凝胶。通过设计水凝胶基体网络组成，调节水凝胶基体高分子与PPy纳米管导电骨架的结合方式，项目发展了一种能够实现规模化构筑导电高分子水凝胶的方法。项目完成的主要工作包括；(1) 系统地优化了PPy纳米管的合成条件，获得的PPy纳米管电导率最高可达130 S/cm，并探讨了在甲基橙和三氯化铁协同作用下PPy纳米管的形成机理。(2)构建了以共价交联PVA网络和动态离子交联的PAA网络作为水凝胶基体的导电水凝胶，确保了水凝胶优异的强度和韧性，其拉伸强度达到3MPa、断裂伸长率超过300%。(3)采用大长径比的PPy纳米管在水凝胶中构筑了高效的导电通路，在极低的导电组分含量下(~0.6%)即可达到可观的电导率(5~11 S/m)。该种水凝胶，能够灵敏监测人体的手指弯曲和手腕伸展等肢体运动，有望作为一种具有广泛适用性的柔性传感材料。项目研究工作对于发展高性能、低成本的柔性传感材料，拓展导电高分子的应用空间具有重要的参考价值。