恒定磁场(0.4 T)对聚苯胺微观取向结构的影响

在恒定磁场(0.4 T)条件下, 采用乳液聚合法合成了十二烷基苯磺酸掺杂聚苯胺(PAn), 并通过透射电子显微镜(TEM)、X射线衍射(XRD)、傅立叶红外光谱(FT-IR)、电导率、产物复合膜电阻率的各向异性, 以及产物间甲酚(m-cresol)溶液的电导率在外电场作用下变化的分析与表征, 系统研究了磁场对PAn的微观取向结构及其性能的影响. 实验结果表明, 与无磁场条件下制备的聚苯胺(PAn_-O)相比, 磁场条件下制备的聚苯胺(PAn_-M)具有更高的结晶度和明显的微观取向结构, 其微粒有序排列和堆砌成了许多具有一定长/径比的条状聚集体; PAn_-M/PVA(聚乙烯醇)复合膜经磁化成膜, 可以表现出明显的导电性能的各向异性; PAn_-M/m-cresol溶液的电导率, 在有、无外场(电场)作用下存在明显的突变. 分析认为: 由于磁场条件下制备的PAn粉末存在着微观取向和显著的抗磁磁化率的各向异性, 在外磁场作用下其堆砌方式会进一步演变成宏观的取向, 随之表现出物理性能上的各向异性.

Effect of a Constant Magnetic Field (0.4 T) on Orientation Microstructure of Polyaniline

Polyaniline (PAn) doped with dodecyl benzenesulfonic acid was synthesized by emulsion polymerization in the presence of a constant magnetic field (0.4 T). The micro-morphology and orientation microstructure of the PAn were systematically investigated using transmission electron microscopy, X-ray diffraction, FT-IR spectroscopy, conductivity, the resistance anisotropy of the PAn/PVA composite film and the conductivity change of the PAn/m-cresol solution under an external electric field, showing that compared with the PAn_-O synthesized in the absence of a magnetic field, there is significant microcosmically preferred orientation in the PAn_-M synthesized in the presence of a magnetic field, their particles arrange and pack orderly to form plenty of strip aggregates with some ratio of the length to width, and they achieve conforming orientation when magnetized. In addition, the PAn-_M is obviously found to have higher crystallinity. The PAn_-M/PVA composite film cured under a condition of magnetization shows the remarkable anisotropic electrical conductivity. And the m-cresol solution prepared from PAn_-M underwent an obvious abrupt change in its conductivity from the presence of an external electric field to its absence. It was thought that because of the existence of microcosmically preferred orientation, the macroscopic orientation of the PAn_-M was evolved in the presence of an outside magnetic field, and the anisotropic electrical conductivity in this PAn was identified here.