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Author: search.filters.author.Hegde, P.K.Subject: search.filters.subject.Conjugated polymers

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    Nonlinear optical studies on a new poly{2-(biphenyl-4-yl)-5-[3,4- didecyloxy-5-(1,3,4-oxadiazol-2-yl)thiophen-2-yl]-1,3,4-oxadiazole}
    (Trans Tech Publications Ltd ttp@transtec.ch, 2010) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.; Suchand Sandeep, C.S.; Philip, R.
    Measurements of nonlinear optical properties of a newly synthesized thiophene based polymer are reported. The nonlinear transmission measurements were performed on the polymer dissolved in N,N-dimethylformamide by employing the single beam Z-scan technique using a Q-switched laser output at 532-nm. The polymer shows strong optical limiting behavior, where the transmittance decreases when the pump fluence is increased. It was found that an effective three-photon absorption (3PA) model at the excitation wavelength gives the best fit to the obtained experimental data. The value of the 3PA coefficient has been numerically calculated. This study clearly reveals the potential of new polymeric material has, for optical limiting applications. © (2010) Trans Tech Publications.
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    Electrochemical and optical properties of a new donor-acceptor type conjugated polymer derived from 3,4-didodecyloxythiophene
    (Indian Academy of Sciences, 2010) Hegde, P.K.; Vasudeva Adhikari, A.V.; Manjunatha, M.G.
    In this communication, we report the synthesis and characterization of a new donor-acceptor type conjugated polymer carrying alternate 3,4-didodecyloxythiophene and (1,3,4-oxadiazol-yl)pyridine moieties and evaluation of its optical and electrochemical properties. The polymer was synthesized through precursor polyhydrazide route. It has well defined structure, stability and it shows good solubility in common organic solvents. Optical and electrochemical properties were studied by UV-visible, fluorescence spectroscopy and cyclic voltammetric studies, respectively. It displays bluish-green fluorescence both in solution and in film state. Cyclic voltammetric studies showed that the polymer P1 possesses a HOMO energy level of -6-01 and LUMO energy level of -3-34 eV. The preliminary studies clearly reveal that the new polymer can have potential application in the fabrication of light emitting diodes. The studies on its device application are in progress. © Indian Academy of Sciences.
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    Optical and electrochemical properties of a new donor-acceptor type conjugated polymer derived from thiophene, carbazole and 1,3,4-oxadiazole units
    (Trans Tech Publications Ltd ttp@transtec.ch, 2010) Manjunatha, M.G.; Vasudeva Adhikari, A.V.; Hegde, P.K.
    A new donor-acceptor type poly[3-{5-[3,4-didecyloxy-5-(1,3,4-oxadiazol-2- yl)thiophen-2-yl]-1,3,4-oxadiazol-2-yl}-9-dodecyl-9H-carbazole] (P) has been synthesized starting from thiodiglycolic acid and 9H-carbazole through multistep reactions. The polymer has been synthesized through precursor polyhydrazide route. The weight average molecular weight of the polymer was found to be 7210. The polymer exhibited intense green fluorescence in solid sate. Cyclic voltammetric experiments showed that the polymer has low-lying LUMO (-3.55 eV) and high lying HOMO (-5.77 eV) energy levels due to the presence of alternate donor and acceptor units. The optical and electrochemical studies reveal that the new polymer (P) is a promising material for the development of polymer light emitting diodes (PLEDs). © (2010) Trans Tech Publications.
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    Synthesis and characterization of a new NLO-active donor-acceptor-type conjugated polymer derived from 3,4-diphenylthiophene
    (2010) Manjunatha, M.G.; Vasudeva Adhikari, A.V.; Hegde, P.K.; Suchand Sandeep, C.S.; Philip, R.
    A new donor-acceptor-type conjugated polymer (P1) carrying 3,4-diphenylthiophene, 2,5-dihexyloxybenzene, and 1,3,4-oxadiazole units was synthesized through multistep reactions. The polymer was prepared using a polyhydrazide precursor route. The polymer has a well-defined structure and exhibits good thermal stability, with a decomposition onset temperature in nitrogen of 300 °C. Cyclic voltammetry experiments revealed that the polymer has low-lying LUMO (-3.68 eV) and high-lying HOMO (-5.78 eV) energy levels. The electrochemical band gap was found to be 2.10 eV. The UV-visible absorption spectrum of the polymer presented a maximum at 373 nm, and it displayed bluish-green fluorescence in dilute chloroform solution. The nonlinear optical properties of the new polymer were investigated at 532 nm using the Z-scan technique with nanosecond laser pulses. The polymer exhibited strong optical limiting behavior due to excited state absorption, which was phenomenologically similar to a three-photon absorption (3PA) process. The 3PA coefficient ? was found to be 7×10-22 m3/W2. The studies show that the new polymer (P1) is a promising material for developing efficient photonic devices.
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    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.
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    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.