Fast switching films of nematic side chain copolymers

Liquid crystalline side chain copolymers containing covalently attached dyes have been discussed recently. Due to the chemical bond of the dye to the polymer backbone the crystallization of the dye is efficiently suppressed so that high dye concentrations are achievable. The orientational order of the dyes can be frozen-in by cooling the sample below the glas transition temperature, resulting in a dichroic polymer film. Films of such a kind might be suitable candidates for optical data storage provided small defects can be created and annealed fast enough. We have prepared well aligned homogeneous planar layers of 4 different nematic side chain polymers. The polymers consist of a polyacrylate main chain, dyanobiphenyls or cyanophenyl benzoates as mesogenic groups and a blue anthraquinone dye with a concentration ranging from 10 to 20 per cent by weight respectively. Using a He-Ne-laser (4 mW, 633 nm) we have been able to induce and store texture changes with a resolution of about 1 mic ron. In addition we have measured response times as a function of temperature und applied voltage. Results will be discussed in terms of a possible application in optical data storage.