Synthesis and Characterization of Photorefractive Polymer Containing Electron Transport Material

Abstract

An acrylate type monomer was prepared by the reaction of 2-hydroxyethyl acrylate with 9-oxo-9 H -thioxanthene-3-carboxylic acid 10,10-dioxide and was polymerized using AIBN as an initiator and N, N -dimethylformamide as a solvent to yield a polymer containing a thioxanthene unit (P-THEA). The resulting polymer had a number-average molecular weight of 18 000 and a glass-transition temperature of 113 °C. Photorefractive (PR) composites consisting of P-THEA as an electron-transporting component, 4- N, N -diethylamino- E -β-nitrostyrene (DEANST) as a nonlinear optical chromophore, and butyl 9-oxo-9H-thioxanthene-3-carboxylate 10,10-dioxide (TH- n Bu) as a plasticizer were prepared. These composites had an absorption coefficient of 11−33 cm - 1 at 633 nm and glass-transition temperature of 32−42 °C. A PR device with a thickness of 100 μm was fabricated by sandwiching the PR composite between two ITO coated glasses. The electric field and DEANST concentration dependencies of the gain coefficients and diffraction efficiency were investigated by two-beam coupling and four-wave mixing methods. The electron-transporting nature of PR composite was confirmed by the comparison of the sign of coupling coefficient with that of a PVK-based composite.