Novel Y-type polyester 4 containing 5-methyl-4-{5-(1,2,2-tricyanovinyl)-2-thiazolylazo}resorcinoxy groups as non-linear optical (NLO) chromophores, which are parts of the polymer backbone, was prepared, and its NLO properties were investigated. Polyester 4 is soluble in common organic solvents such as N,N-dimethylformamide and dimethylsulfoxide. Polymer 4 shows a thermal stability up to 250 degrees C from thermogravimetric analysis with glass-transition temperature obtained from differential scanning calorimetry of approximately 94 degrees C. The second harmonic generation (SHG) coefficient (d(33)) of poled polymer film at 1560-nm fundamental wavelength is 8.12 x 10(-9) esu. The dipole alignment exhibits a thermal stability even at 6 degrees C higher than glass-transition temperature (T-g), and no significant SHG decay is observed below 100 degrees C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49:1784-1790, 2011