ORIENTATION-ON-DEMAND THIN-FILMS - CURING OF LIQUID-CRYSTALLINE NETWORKS IN AC ELECTRIC-FIELDS

Electric fields have been used in the processing of thin film, liquid crystal thermosets to produce cured network structures selectively ori ented either parallel or perpendicular to a film substrate. Orientatio n, which depends on both the liquid crystal nature of the thermosets a nd their dielectric anisotropy, is selected by varying the frequency o f the alternating electric field and is locked into a robust network s tructure by a cross-linking reaction that takes place concurrent with orientation. Structural changes and orientation during the curing reac tion were measured in real time with synchrotron x-ray diffraction. Di ffraction studies show that, before curing in a modest electric field of 1 volt per micrometer, reorientation can be induced by changing, fo r example, from a high-frequency (>1000 hertz) to a low-frequency (<50 hertz) electric field, which causes a 90-degree flip in the molecular orientation.