Azo Chromophore-Functionalized Polyelectrolytes. 2. Acentric Self-Assembly through a Layer-by-Layer Deposition Process

We have developed epoxy-based, water-soluble azo polymers containing ionizable groups in the azobenzene functionality. We describe a novel approach of the noncentrosymmetric self-assembly of azobenzene chromophores in these polymers through a layer-by-layer deposition technique. The polymers in solution function as polyelectrolytes and were assembled into multilayers by alternately depositing the ionic azobenzene polymers and commercially available polyelectrolytes of the opposite charge on glass substrates. The chromophores in the multilayer film self-assemble into a noncentrosymmetric order requisite for exhibiting second-order NLO property. NLO coefficients are comparable to the poled, spin-coated films of the same polymer. The self-organization of the chromophores was further verified using transmission electron microscopic (TEM) and electroabsorption spectroscopic studies.