A series of photo addressable polymers bearing azo-naphthol moiety in the polymer side chain containing polymethacrylate backbone were synthesized for NLO applications. Various halogen atoms were substituted in the para position of the side chain azobenzene, and the effects of the substituents were investigated. The polymers were characterized by UV, FT-IR, 1H-NMR and 13C-NMR spectroscopy. The photoisomerization property of all the polymers shows a clear dependence on the size of the halogen, indicating the rate of the switching time in the increasing order of F > Cl > Br > I. The glass transition temperature and thermal stability of the polymers were analyzed by DSC and TGA respectively. The third order nonlinear optical properties of the polymer film were measured by the Z-scan technique using Ar-ion laser and exhibited negative optical nonlinearity. The results revealed that these polymers possess potential applications in nonlinear optics and the value of nonlinear susceptibility for the iodine substituted polymer is higher than the other halogen substituted polymers chosen in the study. © Springer Science+Business Media, LLC 2008.