Anisotropic orientation control of nonpolar organic nanocrystal dispersion by external fields

We have studied the external-field-induced orientation of fibriform polydiacetylene nanocrystals in dispersions that we fabricated through reprecipitation followed by orientational fixation. The polymer employed was poly[1,6-di(N-carbazolyl)2,4-hexadiyne] (polyDCHD). An AC electric field and a magnetic field were both effective agents for controlling the orientation of the nanocrystals in the dispersions; in contrast, we observed no orientational effect when applying a DC electric field. The application of the AC electric and magnetic fields led to different anisotropic orientations of the same dispersed nanocrystals. The degree of orientation depended on the AC frequency and the strength of the AC electric or magnetic field.