This paper reports a new nonlinear optical (NLO) poly(phthalazinone ether ketone) P1 with a high molar density (80%) of chromophore. It has been synthesized by Heck reaction between a brominated poly(phthalazinone ether ketone) P and the NLO chromophore 4. P1 exhibited excellent thermal properties and good solubility due to the presence of the kinked non-planar moiety.. phenyl phthalazinone, along the polymer backbones. DSC indicated that the glass transition temperature (T-g) of P1 was 188 degreesC, and TGA indicated that P1 was thermally stable up to 290 degreesC in both air and argon. The structures of P and P1 were characterized, and the poled films of P1 revealed a second-order nonlinear optical coefficient (d(33)) value of 16.9 pm/V by in situ second harmonic generation measurements at 1064 nm fundamental wavelength. (C) 2004 Elsevier B.V. All rights reserved.