Preparation and Properties of A Novel Y-type Nonlinear Optical Polyester with Dioxybenzylidenecyanoacetate Groups

Methyl 2,4-di-(2'-hydroxyethoxy)benzylidenecyanoacetate (3) was prepared and polymerized with terephthaloyl chloride to yield a novel Y-type polyester 4 containing 2,4-dioxybenzylidenecyanoacetate groups as NLO-chromophores, which constituted parts of the polymer backbone. The resulting polymer 4 is soluble in common organic solvents such as acetone and N,N-dimethylformamide. Polymer 4 showed thermal stability up to 280 T in thermogravimetric analysis with glass-transition temperature obtained from differential scanning calorimetry near 108 degrees C. The second harmonic generation (SHG) coefficient (d(33)) of poled polymer films at the 1064 nm fundamental wavelength was around 3.54 x 10(-9) esu. The dipole alignment exhibited a thermal stability up to near T, and no significant SHG decay was observed below 100 T due to the partial main-chain character of polymer structure, which is acceptable for NLO-device applications.