A novel hyperbranced azo polymer with terminal diazonium groups was synthesized by step-growth polymerization of 4

4′-diamino diphenyl sulphone’s diazonium salts (A2) and benzene-1

3

5tricarboxylic acid tri-2-(N-ethylanilino)ethyl ester (B3) through azo-coupling reaction.4

4′-diamino diphenyl sulphone (0.248 g

1 mmol) was dissolved in a hot homogeneous mixture of glacial acetic acid (7.5 mL) and sulfuric acid (1 mL).Aqueous solution of sodium nitrite (0.166 g

2.4 mmol) in 0.5 mL water was added dropwise into the solution at 0℃ and kept at this temperature for 5 min.The diazonium salt solution of 4

4′-diamino diphenyl sulphone was then added dropwise into the solution of benzene-1

3

5tricarboxylic acid tri-2-(Nethylanilino)ethyl ester (0.326 g

0.5 mmol) in 50 mL DMF at 0℃.After the reaction was carried out at 0℃ for 8 h

the solution containing the diazoniumhyperbranched azo polymer was directly used as the polycation solution.The purchased sodium polystrene sulfonate (PSSA) was used as polyanion.Then the multilayer films were prepared by an electrostatic layer-by-layer deposition method.The self-assembly processes and morphologies of surfaces were characterized by UV-Vis spectra

ellipsometer and AFM.A linear increase of absorbance and thickness was observed as the number of the bilayers increased.Dichroism was optically induced in the self-assembly film under the irradiation of a polarized Ar+ laser beam at 488 nm.After 15 min irradiation of the laser beam at an intensity of 80 mW/cm2

the orientation order parameter of the multilayer film obtained was about 0.02.With interfering illumination of Ar+ laser beams for 30 min

significant surface relief gratings formed on the self-assembly multilayer film were observed.The spatial period and height of the obtained SRGs were about 744 nm and 20 nm

respectively.