Polyimide film containing ultra-fine particles

We have succedded in fabricating a polyimide film with a molecular alignment superior to that obtainable by the conventional rubbing treatment. This phenomenon is realized by means of the dispersion of ultra-fine particles such as carbon and titanium dioxide in the polyimide precursor prior to the fabrication of the polyimide film and the rubbing treatment. The molecular alignment was evaluated with birefringence and infrared dichroism measurements. Further experiments establishe that the adsorption of polyimide molecules on ultra-fine particles is a significant factor in achieving a large orientational anisotropy. A model of the alignment is presented in which the rubbing treatment induces the particles to traverse the surface of the film, causing polyimide molecules adsorbed on them to be elongated in the rubbing direction. A potential application of oriented polymide films is the homogeneous alignment of nematic and smectic liquid crystals.