Synthesis and Nonlinear Optical Properties of Novel T-type Polyester Containing Thiophene with Enhanced Thermal Stability

Abstract

A novel T-type polyester 7 containing 1-(2,5-dioxyphenyl)-2-{5-(1,2,2-tricyanovinyl)-2-thienyl}ethenes as nonlinear optical (NLO) chromophores, which are part of the polymer backbone, was prepared and characterized. Polyester 7 is soluble in common organic solvents such as dimethylsulfoxide and N,N-dimethylformamide. It showed a thermal stability up to <TEX>$300^{\circ}C$</TEX> in thermogravimetric analysis thermogram and the glass-transition temperature (<TEX>$T_g$</TEX>) obtained from differential scanning calorimetry thermogram was around <TEX>$113^{\circ}C$</TEX>. The second harmonic generation (SHG) coefficient (<TEX>$d_{33}$</TEX>) of poled polymer films at 1,560 nm fundamental wavelength was around 1.85 pm/V. The dipole alignment exhibits a greater thermal stability even at <TEX>$10^{\circ}C$</TEX> higher than <TEX>$T_g$</TEX>, and there is no SHG decay below <TEX>$125^{\circ}C$</TEX> due to the partial mainchain character of the polymer structure, which is acceptable for nonlinear optical device applications.