Synthesis and Nonlinear Optical Properties of Novel Y-Type Polyurethane Containing Cyanovinylthiazole

Abstract

A novel Y-type polyurethane 4 containing 5-methyl-4-{5-(1,2,2-tricyanovinyl)-2-thiazolylazo}resorcinoxy groups as nonlinear optical (NLO)-chromophores, which constituted parts of the polymer backbones, was prepared and characterized. Polyurethane 4 is soluble in common organic solvents such as acetone and N,N-dimethylformamide. It showed a thermal stability up to 250°C in thermogravimetric analysis thermogram and the glass-transition temperature (T _g ) obtained from differential scanning calorimetry thermogram was around 118°C. The second harmonic generation (SHG) coefficient (d ₃₃ ) of poled polymer film at 1560 nm fundamental wavelength was around 8.43 × 10⁻⁹ esu. The dipole alignment exhibited a thermal stability even at 12°C higher than T _g , and there was no SHG decay below 130°C due to the partial main-chain character of the polymer structure, which is acceptable for nonlinear optical device applications.

Keywords:

• Differential scanning calorimetry (DSC)
• NLO
• polyurethane
• relaxation of dipole alignment
• SHG coefficient
• thermogravimetric analysis (TGA)

Acknowledgements

This research was supported by Basic Science Research Program Through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2009-0070572).

Notes

^a Polymer film after poling.

^b SHG coefficients (d ₃₃) were derived from the analysis of measured Maker-fringes [20].

^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 [19].