Theoretical Design, Synthesis, Solvatochromic Studies and Non‐Linear Optical Properties of 3,4‐Ethylenedioxythiophene and 3,4‐ Propylenedioxythiophene based Copolymers

Abstract

Two thiophene based low band gap conjugated copolymers P(EDOT-NA)] and P(PRDOT-NA) were designed and synthesized via direct arylation polymerization. The copolymers were characterized by UV-Vis, IR, Photoluminescence and NMR spectroscopic techniques. HOMO-LUMO energy levels of the copolymers were theoretically calculated by two levels of DFT theories, HSE06 and B3LYP using a 6-31G (d,p) basis set. Thermal properties were evaluated by thermogravimetric analysis. Optical properties of the copolymers showed solvatochromic behavior in different tolune/acetonitrile mixtures. P(EDOT-NA) exhibited a negative solvatochromism in both absorption and emission spectra with a Stoke's shift of 6761 cm À 1 to 7218 cm À 1 . P(PRDOT-NA) was observed with a negative solvatochromism in absorption and positive solvatochromism in emission with Stoke's shift of 7265 cm À 1 to 7891 cm À .1 . Third-order non-linear optical properties of the copolymers were evaluated using the open-aperture Z-scan technique at 532 nm in DMSO solvent. OA Z-scan behavior and optical limiting effect of the copolymers P(EDOT-NA) and P(PRDOT-NA) were studied at 81 μJ, 165 μJ and 300 μJ. Both copolymers exhibited reverse saturable non-linear optical absorption with positive non-linear absorption coefficient β (m/ W) in the range of 10 À 10 . The optical limiting threshold values obtained for the polymers at 81 μJ were 0.026 GW/cm 2 and 0.033 GW/cm 2 .