Abstract
2,4-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-1-(2,2-dicyanovinyl)benzene dianhydride (4) was prepared and reacted with 1,4-phenylenediamine and 4,4′-oxydianiline to yield novel Y-type polyimides 5-6 containing 2,4-dioxybenzylidenemalononitrile groups as NLO-chromophores, which constitute parts of the polymer backbone. The resulting polyimides 5-6 are soluble in polar solvents such as dimethylsulfoxide and N,N-dimethylformamide. Polymers 5-6 showed a thermal stability up to 330°C in thermogravimetric analysis thermograms with T g values obtained from differential scanning calorimetry thermograms in the range 179–188°C. The second harmonic generation (SHG) coefficients (d 33) of poled polymer films at the 1064 nm fundamental wavelength were around 6.32 × 10−9 esu. The dipole alignment exhibited exceptionally high thermal stability even at 20°C higher than T g , there was no SHG decay below 200°C because of the partial main chain character of polymer structure, which is acceptable for nonlinear optical device applications.
Acknowledgments
This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund, KRF-2007-313-C00498).
Notes
a Determined from DSC curves measured on a TA 2920 differential scanning calorimeter with a heating rate of 10°C/min under nitrogen atmosphere.
b Determined from TGA curves measured on a DuPont 951 thermogravimetric analyzer with a heating rate of 10°C/min under nitrogen atmosphere.
a Polymer film after corona poling.
b SHG coefficients (d 33) were derived from the analysis of measured Maker-fringes [Citation16].
c Order parameter Φ = 1 − A1/A0, where A0 and A1 are the absorbances of the polymer film before and after corona poling, respectively.
d Film thickness was determined by the optical transmission technique [Citation15].