Faculty Publications
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Item Synthesis and nonlinear optical characterization of new poly{2,2?-(3,4-didodecyloxythiophene-2,5-diyl)bis[5-(2-thienyl)-1,3,4-oxadiazole]}(2009) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.; Philip, R.A new donor-acceptor type poly{2,2?-(3,4-didodecyloxythiophene-2,5-diyl)bis[5-(2-thienyl)-1,3,4-oxadiazole]} (P) was synthesized starting from thiodiglycolic acid and diethyl oxalate through multistep reactions. The polymerization was carried out using chemical polymerization technique. The optical and charge-transporting property of the copolymer was investigated by UV-vis, fluorescence emission spectroscopic and cyclic voltammetric studies. The copolymer shows UV absorption maxima at 375 nm and displays bluish-green fluorescence in DMF solution. Its electrochemical band gap was determined to be 2.07 eV. The nonlinear optical (NLO) properties of the copolymer was investigated at 532 nm using single beam Z-scan and degenerate four-wave mixing (DFWM) techniques with nanosecond laser pulses. The copolymer exhibits strong optical limiting behavior due to effective three-photon absorption (3PA). Values of the effective 3PA coefficient (?), third-order nonlinear susceptibility (?(3)) and figure of merit (F) have been calculated. © 2009 Elsevier B.V. All rights reserved.Item Optical characterization of a new Donor-acceptor type conjugated polymer derived from 3,4-diphenylthiophene(2009) Manjunatha, M.G.; Vasudeva Adhikari, A.V.; Hegde, P.K.; Suchand Sandeep, C.S.; Philip, R.A new donor-acceptor type poly{2-(3,4-didecyloxythiophen-2-yl)-5-[3,4- diphenyl-5-(1,3,4-oxadiazol-2-yl)thiophen-2-yl]-1,3,4-oxadiazole} (P1) has been designed and synthesized starting from thiodiglycolic acid, 1,2-diphenylethane- 1,2-dione, and diethyl oxalate through multi-step reactions using precursor polyhydrazide route. The charge-transporting and linear optical property of the polymer has been investigated by cyclic voltammetric, UV-visible, and fluorescence emission spectroscopic studies. The UV-visible absorption spectrum of polymer in thin film form showed maxima at 420 nm. The polymer displayed bluish-green fluorescence both in solution and thin film form. The optical band gap is determined to be 2.27 eV. Third-order nonlinear optical property of the new polymer has been investigated at 532 nm using single beam Z-scan and degenerate four wave mixing (DFWM) techniques with nanosecond laser pulses. The absorptive nonlinearity observed for the polymer P1 is of optical limiting type, which arises due to an "effective" three-photon absorption (3PA) process. The third-order nonlinear optical susceptibility (?(3)) of the polymer is found to be 0.831 × 10-12 esu. Both linear and nonlinear optical studies revealed that the new polymer (P1) is a promising material for applications in photonic devices. © 2009 Springer Science+Business Media, LLC.Item A new donor-acceptor type conjugative poly{2-[4-(1-cyanoethenyl)phenyl]-3- (3,4-didodecyloxythiophen-2-yl)prop-2-enenitrile}: Synthesis and NLO studies(2010) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.; Philip, R.This research article describes a technique to synthesize a new donor-acceptor type conjugated polymer carrying cyanophenylenevinylene and 3,4-didodecyloxy thiophene moieties, as an effective optical limiting material. It also includes the evaluation of its linear and nonlinear optical properties and electrochemical studies. The new polymer, viz., poly{2-[4-(1-cyanoethenyl) phenyl]-3-(3,4-didodecyloxythiophen-2-yl)prop-2-enenitrile} (P1) has been synthesized starting from 2,2?-sulfanediyldiacetic acid and diethyl ethanedioate through multistep reactions. In the final step, the polymerization was brought about by Knovenagel condensation. The newly synthesized intermediate, monomer and the polymer (P1) have been characterized by different spectroscopic techniques followed by elemental analysis. Its optical and electrochemical properties are investigated by UV-vis, fluorescence spectroscopy and cyclic voltammetric studies, respectively. The red colored polymer has a well defined structure, good thermal stability and a band gap of 1.78 eV. It emits green fluorescence both in solution and in film state. The third-order nonlinear optical property (NLO) of the polymer was studied by the Z-scan technique. The measurements were performed at 532 nm with 5 ns laser pulses using samples in solution form. An absorptive nonlinearity of the optical limiting type was found in this polymer, which is due to the combined action of saturable absorption and excited state absorption processes. These studies revealed that polymer P1 is a promising material for optical limiting applications. © 2010 Elsevier B.V.Item Nonlinear optical studies on new conjugated poly{2,2 l-(3,4- dialkoxythiophene-2,5-diyl) bis[5-(2-thienyl)-1,3,4-oxadiazole]}s(2010) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.; Philip, R.Three new donor-acceptor type poly{2,2 1-(3,4-dialkoxythiophene- 2,5-diyl)bis[5-(2-thienyl)-1,3,4-oxadiazole]}s (P1, P2, and P3) were synthesized starting from thiodiglycolic acid and diethyl oxalate through multistep reactions. The polymerization was carried out using chemical polymerization technique. The optical and charge-transporting properties of the polymers were investigated by UV-visible, fluorescence emission spectroscopic and cyclic voltammetric studies. The polymers showed bluish-green fluorescence in solutions. The electrochemical band gaps were determined to be 2.03, 2.09, and 2.17 eV for P1, P2, and P3, respectively. The nonlinear optical properties of new polymers were investigated at 532 nm using single beam Z-scan and degenerate four-wave mixing (DFWM) techniques with nanosecond laser pulses. The polymers exhibited strong optical limiting behavior due to "effective" three-photon absorption. Values of the effective three-photon absorption (3PA) coefficients, thirdorder nonlinear susceptibilities (? (3)), and figures (F) of merit were calculated. © 2010 Wiley Periodicals, Inc.Item Novel poly(3,4-dialkoxythiophene)s carrying 1,3,4-oxadiazolyl-biphenyl moieties: Synthesis and nonlinear optical studies(2011) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.; Philip, R.Two new donor-acceptor types of polymer, poly{2-(biphenyl-4-yl)-5-[3,4-dialkoxy-5-(1,3,4-oxadiazol-2-yl)thiophen-2-yl]-1,3,4-oxadiazole}s, were synthesized starting from 2,2'-sulfanediyldiacetic acid and diethyl ethanedioate through multi-step reactions. The polymerization was carried out via the polyhydrazide precursor route. The optical and charge-transporting properties of the polymers were investigated using UV-visible and fluorescence emission spectroscopic and cyclic voltammetric studies. The polymers showed bluish-green fluorescence in solutions. The electrochemical band gaps of the polymers were determined to be 2.16 and 2.22 eV. The nonlinear optical properties of the polymers were investigated at 532 nm using the single-beam Z-scan technique with nanosecond laser pulses. The polymers showed strong optical limiting behaviour due to effective three-photon absorption. The values of the three-photon absorption coefficients for the polymers were found to be 9 × 10-24 and 17 × 10-24 m3 W-2, which are comparable to those of good optical limiting materials. © 2010 Society of Chemical Industry.Item Synthesis, electrochemical and optical studies of new cyanopyridine based conjugated polymers as potential fluorescent materials(Elsevier Ltd, 2011) Vishnumurthy, K.A.; Sunitha, M.S.; Safakath, K.; Philip, R.; Vasudeva Adhikari, A.V.In this communication we describe the design and synthesis of four new conjugated polymers (P1-P4) carrying cyanopyridine in their backbone via Wittig condensation technique. Their structures were well established by FTIR, 1H NMR, elemental analysis and gel permeation chromatographic techniques. They exhibited good thermal stability with the onset decomposition temperature around 300-350 °C in nitrogen atmosphere. Further, their electrochemical, linear and third-order non-linear optical properties have been investigated. The polymers showed low electrochemical band gaps in the range of 1.77-1.99 eV and displayed very good fluorescence emission property in various polar solvents. The fluorescence quantum yields of polymers P1-P4 in tetrahydrofuran (THF) were found to be 35, 42, 38 and 34%, respectively. The effective two-photon absorption coefficients (?) for the polymers were determined by Z-Scan technique and were found to be 1.34 × 10 -11, 1.24 × 10-11, 3.04 × 10-11 and 1.85 × 10-11 m/W for polymers P1-P4, respectively. © 2011 Elsevier Ltd. All rights reserved.Item Nonlinear optical characterization of new thiophene-based conjugated polymers for photonic switching applications(2011) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.S.; Philip, R.This research article describes a technique to synthesize new donor-acceptor-type conjugated polymers carrying 1,3,4-oxadiazolyl-naphthalene and 3,4-(ethylenedioxy/diphenyl)-thiophene moieties (P1 and P2) starting from 2,2?-sulfanediyldiacetic acid and diethyl ethanedioate through multistep reactions. The newly synthesized intermediates and the final polymers have been characterized by different spectroscopic techniques followed by elemental analysis. Their optical and electrochemical properties have been investigated by UV-visible, fluorescence spectroscopy, and cyclic voltammetric studies, respectively. Furthermore, the nonlinear optical transmission properties of these polymers have been investigated by the open aperture z-scan technique. The new polymers P1 and P2 have well-defined structures, good thermal stability, and band gaps of 1.98 and 1.88 eV, respectively. They emit bluish-green fluorescence both in solution and in film state. Interestingly, these polymers show saturable absorption behavior. The results of nonlinear optical studies reveal that they are potential candidates for photonic switching device applications. © 2011 Wiley Periodicals, Inc.Item New diphenylamine-based donor-acceptor-type conjugated polymers as potential photonic materials(2011) Vishnumurthy, K.A.; Sunitha, M.S.; Philip, R.; Vasudeva Adhikari, A.V.A new series of donor-acceptor-type conjugated polymers (P1 and P2) carrying a diphenyl amine moiety were synthesized via Wittig condensation technique. The polymers structures were well established by FT-IR, 1H NMR, elemental analysis and gel permeation chromatographic techniques. They exhibited good thermal stability with an onset decomposition temperature of approximately 325 °C under nitrogen atmosphere. The optical and electrochemical properties of the polymers were studied by UV-vis, fluorescence emission spectroscopy and cyclic voltammetry. They exhibited good fluorescence in dilute solutions and showed solvatochromic behavior in various polar solvents. The electrochemical studies revealed that the polymers possess low-lying LUMO energy levels that ranging from -3.47 to -3.73 eV and high-lying HOMO energy levels that ranging from -5.57 to -5.81 eV. The thirdorder nonlinear optical properties of the polymers were investigated using the Z-scan technique. The effective two-photon absorption (TPA) coefficients (?) of the polymers were found to be 0.645 × 10-10 and 0.212 × 10-10 m/W. © 2011 Elsevier Ltd. All rights reserved.