Synthesis and properties of novel nonlinear optical polyurethane containing 4-(2′-carbomethoxy-2′-cyano)vinyl-5-nitrocatecholic group

ABSTRACT

A new X-type polyurethane (5) containing 4-(2′-carbomethoxy-2′-cyano)vinyl-5-nitrocatecholic groups as NLO chromophores, which are components of the polymer backbone, was prepared. Polyurethane 5 is soluble in common organic solvents such as N,N-dimethylformamide and dimethylsulfoxide. It shows a thermal stability up to 280°C from thermogravimetric analysis with glass-transition temperature (T_g) obtained from differential scanning calorimetry near 93°C. The second harmonic generation (SHG) coefficient (d₃₃) of a poled polymer film at the 1064 nm fundamental wavelength is around 6.58 × 10⁻⁹ esu. The dipole alignment exhibits a thermal stability even at 7°C higher than T_g, and no SHG decay was observed below 100°C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.

KEYWORDS:

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

Funding

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2015R1D1A1A09058972).