SYNTHESIS AND CHARACTERIZATION OF DENDRITIC ARCHITECTURE CONTAINING PUSH-PULL CONJUGATED ORGANIC CHROMOPHORE POSSESSING
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0937-M03-32
SYNTHESIS AND CHARACTERIZATION OF DENDRITIC ARCHITECTURE CONTAINING PUSH-PULL CONJUGATED ORGANIC CHROMOPHORE POSSESSING NONLINEAR OPTICAL PROPERTY Jin Joo Choi, Jong Sun Lim, Changjin Lee, and Dong Wook Kim Advanced Materials Division, Korea Research Institute of Chemical Technology, 100 Jangdong Yusungku, Daejeon, 305-600, Korea, Republic of
ABSTRACT We designed and synthesized a dendritic architecture in which three branches of the NLOactive component consisting of push-pull type conjugated structure were linked onto its core. Chemical structure of the dendritic nonlinear optical (NLO) chromophore was verified by NMR spectroscopy, which clearly showed that the conjugated bridge had a trans-conformation. The dendrimer exhibited that the broad absorption band centered at around 608 nm extending to 760 nm. It was thermally stable up to 275 oC in the nitrogen atmosphere. Polymer film was prepared by spincoating the solution of mixture of amorphous polycarbonate (APC) and the dendritic chromophore, which exhibited an electro-optic coefficient of 19 pm/V at 1.55 µm wavelength. INTRODUCTION Since the first NLO polymer was reported in 1982, most of the researchers have focused on synthesizing the organic chromophores possessing high molecular hyperpolarizability (β) and dipole moment (µ) in order to enhance their second-order nonlinear susceptibility (χ(2)) [1]. However, recent experiment and molecular simulation have suggested that it is difficult for high µβ chromophores at high loading density to be aligned in the direction of the applied electric field, due to their high ground-state dipole moment interactions between the neighboring molecules [2]. The large void-containing dendritic structures may provide an attractive solution to this problem because the dendrons can effectively decrease the interactions among chromophores due to the steric effect [3-4]. Furthermore, these materials are mono-disperse, well defined, and easily purified when compared to polymers that are made by the conventional synthetic approaches. In this work, we report a NLO chromophore adopting dendritic architecture, in which three branches of the NLO-active component were linked with the core. The NLO-active component contains a phenylene ring substituted with a bulky alkyl chain as a conjugation bridge. The NLO dendrimer was successfully synthesized and verified by NMR spectroscopy, thermal instruments and absorption spectroscopy. High quality thin films were prepared by spincoating a solution of the dendrimer and a polymer host. Macroscopic optical nonlinearities were also evaluated from the poled film by a simple reflection method.
EXPERIMENT Materials Poly(bisphenol A carbonate-co-4,4’-(3,3,5-trimethylcyclohexylidene) diphenol (APC) was purchased from Aldrich and purified by reprecipitating the polymers in methanol several times. Diethyl-[2,5-bis(2-ethyl-hexyloxy)-4-bromophenyl] methylphosphonate (compound 3 in Scheme 1) and 2-cyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) were prepared according to the liter
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