Theoretical design, synthesis, characterization and solvatochromic studies and non-linear optical properties of poly[] copolymer

A donor-acceptor type [pi]-conjugated conducting, poly[( 2,3,5,6- tetrafluorophenyl)-2,3-dihydro-thieno[3,4-b][1,4]dioxine)], P(EDOT-4FPH) was designed and synthesized by direct arylation polymerization method. Computational calculations for the monomers, oligomers, and copolymer were performed using Gaussian 09 with two hybrid functional, B3LYP and HSE06 using (6-31G (d,p)) basis set. Theoretical band gap obtained from HSE06 (6-31G/d,p) basis set was 2.94 eV. The polymer was characterized by FTIR, .sup.1H NMR, EDX, and TGA. The Electrochemical band gap was determined by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV). The values were 1.81 eV,1.71 eV and 1.64 eV. Optical band gap was observed to be 2.05 eV. Photophysical studies were performed and the copolymer exhibited lifetime decay of 0.55 ns and quantum yield of 0.37 in chloroform solution. It showed positive solvatochromism with a large Stoke's shift from 2310 cm.sup.-1 to 4152 cm.sup.-1 in solutions of varying polarity. Third-order non-linear optical properties of the copolymer P(EDOT-4FPH) were observed using the open-aperture Z-scan technique at 532 nm in DMSO solvent. OA Z-scan trace and optical limiting effect of the copolymer were studied at different laser intensities. At 10 [micro]J, the lowest optical threshold of 0.005 GW/cm.sup.2 was found with reverse saturable non-linear absorption and non-linear absorption coefficient of 3.63 x 10.sup.-9 m/W.