An A2+B3 method of preparing hyperbranched azo polymers by azo-coupling reactions was described.The hyperbranched precursor with diazonium salt groups on the periphery was prepared by step-growth polymerization of A2(diazonium salts of 4

4′-diamino diphenyl sulphone)/B3(benzene-1

3

5-tricarboxylic acid tri-2-(N-ethylanilino)ethyl ester)monomers through azo-coupling reaction.Benzene-1

3

5-tricarboxylic acid tri-2-(N-ethylanilino)ethyl ester was prepared by Schotten-Baumann reactions between 1

3

5-benzenetricarbonyl chloride and N-ethyl-N-hydroxyethyl-aniline.Then the hyperbranched precursor with diazonium salt groups on the periphery was further reacted with N

N-diethyl aniline by azo-coupling reaction to obtain the final hyperbranched azo polymer.The azo polymer was characterized by the spectroscopic methods and thermal analysis.The phase transition behavior of the hyperbranched azo polymer was studied by using the differential scanning calorimetry (DSC).The hyperbranched polymer showed a second-order phase transition of typical amorphous substances.The Tg of the hyperbranched azo polymer was about 161℃.As containing the donoracceptor type azo chromophores

the polymer showed typical spectral characteristics of the pseudo-stilbene type azo chromophores.The λ-max value of the hyperbranched azo polymer

corresponding to the π-π transition

was about 465 nm.Spin-coated thin films of the hyperbranched azo polymer were used to carry out the SGR inscription experiments.Two p-polarized Ar+ laser beams (488 nm) with an intensity 80 mW/cm2 were used to produce the interference pattern on the polymer film.After irradiated for 1000 s at room temperature

the surface modulation depth was about 100 nm

and the grating spacing was about 730 nm.The modulation depth depended on the irradiation energy

and the spatial period depended on both the angle between the two interfering beams and the wavelength of the writing beams.Complex patterns could be inscribed when two gratings were recorded orthogonally to each other at the same location.