Molecular Design, Synthesis, and Properties of Y-Type Nonlinear Optical Polyester Containing Tricyanovinylthiophene with Enhanced Thermal Stability of Second Harmonic Generation

摘要

1-{3,4-Di-(2-hydroxyethoxy)phenyl}-2-(2-thiophenyl)ethene (5) was prepared and condensed with terephthaloyl chloride to yield polyester (6). Polymer 6 was reacted with tetracyanoethylene to give a new Y-type polyester (7) containing 1-(3,4-dioxyethoxy)phenyl-2-{5-(2,2,3-tricyanovinyl)-2-thiophenyl)}ethen yl groups as NLO-chromophores, which are components of the polymer backbones. Polyester 7 is soluble in common organic solvents such as N,N-dimethylformamide and acetone. Polymer 7 showed a thermal stability up to 300 degrees C in thermogravimetric analysis with glass transition temperature (T-g) obtained from differential scanning calorimetry near 126 degrees C. The second harmonic generation (SHG) coefficient (d(33)) of poled polymer film at the 1560 nm fundamental wavelength was around 6.57 x 10(-9) esu. The dipole alignment exhibited high thermal stability up to the T-g, and there was no SHG decay below 125 degrees C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.