Liquid crystal and cellulose derivatives composites used in electro-optical applications

We have performed a preliminary study by light transmission of the electro- optical behaviour of several cells prepared either from hydroxypropylcellul ose (HPC) or HPC with cellulose acetate (CA) (1% w/w) cross linked in both cases with 1,4-diisobutanocianate (BDI) (7%w/w) and different concentration s of a commercial nematic liquid crystal mixture with varying optical aniso tropies. The optical response when the cells are subjected to a short ac el ectric pulse of variable intensity is presented and correlated with the use of CA and the optical anisotropy of liquid crystal mixture used in the cel ls, it was found that cells with CA exhibit much larger contrasts but also a small decrease of the maximum light tr;transmission when compared with ce lls without CA. The anisotropy of the liquid crystal mixture is seen to hav e a strong influence on the electro-optical behaviour of the cells prepared with CA. From scanning electron microscopy (SEM), we found in the surface of the solid films prepared with CA some heterogeneities and porous (2 mu m ) that can be responsible for the strong increase in the contrast observed.