Click chemistry-based synthesis of azo polymers for second-order nonlinear optics

Article abstract of DOI:10.1002/pola.25928

Four linear polymers containing pendant azo moiety were synthesized through click chemistry for second-order nonlinear optical study. The polymers were found soluble in most of the polar organic solvents such as tetrahydrofuran (THF), chloroform, and dimethyl formamide (DMF). The polymers showed thermal stability up to 300 °C and glass transition temperatures (T_g) in the range of 120-140 °C. The molecular weights (M_w) of these polymers (measured by gel permeation chromatography) were in the range 37,900-55,000 g/mol. The polymers were found to form optically transparent films by solution casting from THF solution. Order parameters were calculated from UV-vis absorption spectra. The morphology changes in the films after poling were characterized by atomic force microscopy. The angular dependence, temperature dependence, and time dependence of second harmonic generation (SHG) intensity were obtained by using 1064 nm Nd:YAG laser. The SHG intensity remained unchanged up to 95 °C. At room temperature, it remained stable up to 8 days after initial drop of about 14%.