Electrooptical properties of poly(diisopropyl fumarate‐co‐styrene)/cyanobiphenyl‐type liquid crystal composite films

Composite films composed of poly(diisopropyl fumarate-co-styrene) (PFS) and nematictype liquid crystal (E8) (40/60 by weight) were prepared by solvent casting in chloroform at room temperature. Scanning electron microscopy measurement showed that a liquid crystal phase is continuously embedded in a spongy-like PFS martrix. Optical responses of the composite films under the conditions of an externally imposed ac electric field (60–240 Vp-p, 10–1000 Hz), temperature (290–355 K), and a film thickness (8–16 μm), were determined using an He–Ne laser (wavelength 632.8 nm). The results obtained indicated that, under the conditions imposed, the output can be continuously controlled, and the response time is only of several milliseconds or less. In addition, the response to temperature sweep, heating and cooling, was reversible with only a delay, and it was interpreted in terms of the rigidity and thermal stability of the matrix polymer. © 1993 John Wiley & Sons, Inc.