The effect of pH value on the electrostatic layer-by-layer selfassembly and the photoresponsive behavior of on azo polyelectrolyte Poly{2-［4-(4′-ethoxyphenylazo)phenoxy］ethyl acrylate-co-acrylic acid} (PEAPE). Results show that in the studied pH value range

the lower the pH value

the higher is the UV-Vis absorbance and larger is the thickness of the multilayer films.FTIR studies indicate that the azo polyelectrolyte exhibits a different ionization degree in the solutions with different pH values.The higher absorbance and larger thickness of the layer-by-layer films can be attributed to the low ionization degree and the shrinkage conformation of PEAPE in solutions with the low pH value. FTIR analysis also confirms that the driving force for layer-by-layer self-assembly of PEAPE and poly(diallydimethyl ammoniumchloride) is the electrostatic interaction.