Electric field-induced orientation of organic microcrystals with large dipole moment in dispersion liquid

The reprecipitation method is a useful technique to fabricate organic micro crystals such as polydiacetylene, low-molecular weight aromatic compounds, organic functional dyes, which features are located in a mesoscopic phase b etween a single molecule and bulk crystals, and peculiar optical and electr onic properties are expected to be exhibited in organic microcrystals. By u sing this technique, we succeeded in fabricating polar organic microcrystal s such as 4'-dimethylamino-N-methylstilbazolium p-toluenesulfonate (DAST) d ispersed in decalin with low dielectric constant. The resulting DAST microc rystals were confirmed to be second-harmonic generation (SHG)-active from t he measurements with powder test and powder X-ray diffraction (XRD), which means that DAST microcrystals have dipole moment. Actually, it has become a pparent from absorbance changes that DAST microcrystals in the dispersion l iquid were oriented by applying remarkably lower DC electric field, in comp arison with DC electric field in common LC displays. The present DAST micro crystals-dispersion liquid would serve both as crystal property and liquid one. In other words, this system can be regarded as a new concept of liquid and crystals' system, which will be expected to be applied to novel optica l devices in electronics and photonics fields. (C) 2000 Elsevier Science B. V. All rights reserved.