Synthesis and Nonlinear optical Properties of Novel Y-Type Polyesters with Enhanced Thermal Stability of Second Harmonic Generation

2,3-Di-(2’-hydroxyethoxy)-4’-nitrostilbene (3) was prepared and condensed with terephthaloyl chloride, adipoyl chloride, and sebacoyl chloride to yield novel Y-type polyesters (4-6) containing the NLO-chromophores 2,3-dioxynitrostilbenyl groups, which constituted parts of the polymer backbones. Polymers4-6 were soluble in common organic solvents such as acetone andN,N-dimethylformamide. Polymers4-5 showed thermal stability up to 300 °C in thermogravimetric analysis with glass transition temperatures (Tg), obtained from differential scanning calorimetry, in the range 81–95 °C. The second harmonic generation (SHG) coefficients (d33) of the poled polymer films at the 1064 nm fundamental wavelength were around 3.68 × 10−9 esu. The dipole alignment exhibited high thermal stability up toTg, and there was no SHG decay belowTg due to the partial main-chain character of the polymer structure.