| 초록 |
Nonlinear optical (NLO) polymers are considered as a good candidate for making electro-optic (EO) devices, mainly because they offer many advantages. In the developments of NLO polymers for EO device applications, stabilization of electrically induced dipole alignment is important. Polyurethane matrix forms extensive hydrogen bond between urethane linkage and increases rigidity preventing the relaxation of induced dipoles. Physically crosslinked systems via hydrogen bonds have the advantages such as homogenity and good processibility relative to the chemically crosslinked systems. In this work we prepared novel Y-type polyurethanes containing 3,4-dioxynitrostilbene as a NLO-chromophore. 3,4-Di-(2-hydroxyethoxy)-4-nitrostilbene (2) was prepared by the reaction of 2-iodoethanol with 3,4-dihydroxy-4-nitrostilbene (1). Diol 2 was condensed with 2,4-toluenediisocyanate, 3,3-dimethoxy-4,4-biphenylenediisocyanate, and 1,6-hexamethylenediisocyanate to yield novel Y-type polyurethanes 3-5 containing dioxynitrostilbene as a NLO-chromophore. Polymers 3-5 were soluble in common organic solvents such as acetone and DMF. These polymers showed a thermal stability up to 280oC in TGA thermograms with Tg values in the range of 100-143oC in DSC thermograms. The approximate lengths of aligned NLO-chromophores of the polymers estimated from AFM images were around 2 nm. The SHG coefficients (d33) of poled polymer films were around 4.5 x 10-8 esu. |
