Thermally crosslinkable second-order nonlinear optical polymer using pentaerythritol tetrakis(2-mercaptoacetate) as crosslinker

Abstract

Two kinds of second-order nonlinear optical copolymers were prepared by the copolymerization of the vinyl monomers containing NLO chromophore, methacrylic acid, and methyl methacrylate or butyl methacrylate. Glass transition temperatures (T-g) of copolymers were around 130 degrees C. The copolymers were soluble in common organic solvents such as tetrahydrofuran (THF), cyclohexanone, and N,N-dimethylformamide (DMF). The crosslinked copolymer was obtained by thermal treatment using pentaerythritol tetrakis(2-mercaptoacetate) as a crosslinker and became insoluble in tetrahydrofuran (THF) and N,N-dimethylformamide (DMF). Poling was carried out at 120 degrees C for 20 min and identified with UV-Vis spectroscopy. Electro-optic coefficient (r(33)) measurement showed a value of 35 pm/V for polymer 2 at 633 nm. Temporal stability of copolymers was improved owing to the crosslinked network, which was successfully obtained at 170 degrees C for 30 min after poling.