Nonlinear optical polyimide/montmorillonite nanocomposites consisting of azobenzene dyes

A reactive organoclay was formed using trifunctional 1,1,1-tris[4-(4-amino-2-trifluoromethylphenoxy)phenyl] as a swelling agent for the silicate layers of montmorillonite. One of the functional groups of the swelling agents formed an ionic bond with the negatively charged silicates, whereas the remaining functional groups were available for further reaction with poly(amic acid) end capped with anhydride groups. Subsequently, the hydroxyl groups of the ensuing polyimide could be further reacted with isocyanate-containing dyes to form nonlinear optical polyimides with high Tgs. X-ray diffraction and transmission electron microscopy revealed that the dispersion of silicate layers in the polyimide created an exfoliated structure as a result of using the trifunctional groups of the swelling agent. This particular structure of the nanocomposite resulted in enhanced thermal properties and excellent optical transparency. Using in situ contact poling, r33 coefficients ranging from 4.6 to 7.6 pm/V were obtained for the organic/inorganic NLO materials; excellent temporal stability at 100 °C was obtained.