Preparation of azo polyelectrolyte self-assembled multilayers by using N, N-dimethylformamide/H2O mixtures as solvents

Abstract

N,N-Dimethylformamide (DMF)/H₂O mixtures were used as solvents to fabricate azo polyelectrolyte (PEAPH)/poly(diallyldimethyl ammonium chloride)(PDAC) self-assembled multilayers with the layer-by-layer electrostatic adsorption technique. PEAPH is a copolymer of acrylic acid and azobenzene-containing acrylate. The effect of the ratio of DMF to water on the multilayer growth, structure and surface morphology was studied in some details. Results show that DMF/H₂O mixtures are proper media for PEAPH/PDAC multilayer fabrication. The ratio of DMF to water in the mixture has significant influence on the multilayer structure and surface morphology. With the increase of DMF content, the multilayer thickness has a better linear growth relationship with the bilayer number, and the multilayer surface becomes smoother. Moreover, azo chromophores show less H-aggregation when the multilayers are fabricated from DMF/H₂O mixtures with higher DMF contents. These studies demonstrate that using organic solvent and water mixtures is an effective way to control the multilayer construction by adjusting the media properties. This method can be applied to multilayer fabrication of other water-insoluble polyelectrolytes.