- Email: [email protected]
Electrochemical synthesis of free-standing polyacetylene film with copper catalyst
ELSEVIER
Synthetic
Metals
101 (1999)
58
Electrochemical synthesis of free-standing polyacetylene film with copper catalyst M. Kijima, * K. Ohmura, H. Shirakawa Institute of Materials Science, University of Tsukuba,Tsukuba. Ibaraki 305-8573,Japan Abstract
Acetylenewaspotentiostaticallyelectropolymerizedin the presenceof a Cu-TMEDA catalystin DMF containingLiClO, underan argonatmosphere, affording a black filmy productdepositedon a Pt cathode.The productwasliberatedasa free-standingfilm by a treatmentof methanol.Thefilm wasfound to consistof amorphous pans-richpolyacetylenechainswhosedegreeof polymerizationwas morethan 50 with contaminantssuch as metalsand the electrolyte. SEM analysisof the film surfaceshoweda cauliflower-like morphologywithoutfibliler structures.Electricalconductivityof the film wasabout10Scm” uponI, doping Kepords: Polyacetylene,Electrochemical polymerization,InfraredandRamanspectroscopy, Amorphousthin film 1. Introduction
A variety of synthetic routes have been investigatedfor polyacetylene[I]. The most widely usedmethodfor preparing high-quality, free-standing films of polyacetylene is polymerizationof acetyleneby Ziegler-Nattacatalysts.Electropolymerizationis a usefil methodfor synthesisof conducting polymerin a form of film asdemonstrated by a seriesof aromatic monomers,pyrrole, thiopheneand aniline.However,so far only oneresearchgrouphasdealt with the electrochemical synthesis of polyacetylene.Thus, Chen et al 121reported an intractable depositon Pt. Recently, we have attemptedfor synthesisof a carbynoidmaterialby an anodiccondensation of acetylene131.In this case,a black filmy productconsistingof polyacetylenewas formed on the cathode.Here we report characterizationof the filmy product and investigation of the polymerization mechanism. 2. Experimental
A DMF solutionof acetylene(1.4 mol dmm3) containing0.1 mol dm-’ of LiCIO, and 4.6 mmoldmm3 of CuCl and 0.14 GoI dme3of N.N,N’,N’-tetramethylethylenediamine (TMEDA) was potentiostaticallyelectrolyzedwith a Pt platecathodeat a voltage during-2.0 k-3.0 V (vs. SCE)in a onecompartment cell at 40°C. After 15 h, the Pt cathodewasseparated from the vesselandwas washedwith DMF, CH,CN, and MeOH, succesivelyunderan argon atmosphereliberating a black filmy product from the electrodewith an evolution of H,. The productwasdried under vacuum affording a free-standingfilm about 20-40 pm in thickness. 3. Results and Discussion
Figure 1 showsthe IR spectraof the cathodicproductsand polyacetylenestandardspreparedwith Ziegler-Nattacatalyst.IR spectrumof the film sample(a) showstwo sharppeaksat 1009 and 742 cm-’ which are characteristicof 6,, out-of-planein tram- andc&conjugateddoublebonds,respectively.It shouldbe notedthat the spectrum(a) is quite different from that of the anodicproductreportedpreviously[3]. Fromthe two peakratio, the productconsistsof a pans-rich(transcontentis about60 %)
4000
3000
2000 Wavenumber
1000 (cm’)
Figure1. IR spectra of (a) as-prepared sample, (b) aq.HCl treated sample, (c)truns-polyacetylene, (d)cis-polyacetylene form of polyacetylene.Ramanspectrumof this sampleexcited with 785 run lasershowstwo intenseresonanceRamanpeaksat 1472 and 1079 cm-‘, which also suggeststhe product is polyacetyleneandthe degreeof polymerizationis morethti0. XRD analysisshowsthe product is amorphous.A low carbon content(about46 %) of the productsuggestspresence~of much contaminantsuch as metals and the electrolyte. Electrical conductivity of the film wasabout10 Scm‘]uponI, doping. SEM observation shows a cauliflower-like surface morphologytypical of electropolymerizedmaterials.After an HCl treatment,an absorptionat 3010 cm“ due to vc.Hof h’anspolyacetyleneisappears(figure 1 (b)) with liberationof a Cu ion. Theseresults suggestthat the polymerizationis proceededby an anionicmechanism with assistance of the metalion. 4. References
[I] C. W.Chien,Polyacetylene, Academic Press, 1984;H. Shimka@T. Masuda, K. T&da, in S.Pati (ed.),Supplement C2:TheChemistry of TripleBonded Functional Groups, Wiley,1994,p945. [2] S. -A. Chen,H. -.I. Shy,J. Polym.Sci.,-Polym.Chem.Ed., 23 (1981)2441. [3] K. Ohrnura, M. Kijima,H. Shirakawa, Synth.Met, 84(1997)417.
0379-6779199/$ - seefrontmatter0 1999Elsevier Science S.A. All rightsreserved. PII: SO379-6779(98)01 123-O
Synthetic
Metals
101 (1999)
58
Electrochemical synthesis of free-standing polyacetylene film with copper catalyst M. Kijima, * K. Ohmura, H. Shirakawa Institute of Materials Science, University of Tsukuba,Tsukuba. Ibaraki 305-8573,Japan Abstract
Acetylenewaspotentiostaticallyelectropolymerizedin the presenceof a Cu-TMEDA catalystin DMF containingLiClO, underan argonatmosphere, affording a black filmy productdepositedon a Pt cathode.The productwasliberatedasa free-standingfilm by a treatmentof methanol.Thefilm wasfound to consistof amorphous pans-richpolyacetylenechainswhosedegreeof polymerizationwas morethan 50 with contaminantssuch as metalsand the electrolyte. SEM analysisof the film surfaceshoweda cauliflower-like morphologywithoutfibliler structures.Electricalconductivityof the film wasabout10Scm” uponI, doping Kepords: Polyacetylene,Electrochemical polymerization,InfraredandRamanspectroscopy, Amorphousthin film 1. Introduction
A variety of synthetic routes have been investigatedfor polyacetylene[I]. The most widely usedmethodfor preparing high-quality, free-standing films of polyacetylene is polymerizationof acetyleneby Ziegler-Nattacatalysts.Electropolymerizationis a usefil methodfor synthesisof conducting polymerin a form of film asdemonstrated by a seriesof aromatic monomers,pyrrole, thiopheneand aniline.However,so far only oneresearchgrouphasdealt with the electrochemical synthesis of polyacetylene.Thus, Chen et al 121reported an intractable depositon Pt. Recently, we have attemptedfor synthesisof a carbynoidmaterialby an anodiccondensation of acetylene131.In this case,a black filmy productconsistingof polyacetylenewas formed on the cathode.Here we report characterizationof the filmy product and investigation of the polymerization mechanism. 2. Experimental
A DMF solutionof acetylene(1.4 mol dmm3) containing0.1 mol dm-’ of LiCIO, and 4.6 mmoldmm3 of CuCl and 0.14 GoI dme3of N.N,N’,N’-tetramethylethylenediamine (TMEDA) was potentiostaticallyelectrolyzedwith a Pt platecathodeat a voltage during-2.0 k-3.0 V (vs. SCE)in a onecompartment cell at 40°C. After 15 h, the Pt cathodewasseparated from the vesselandwas washedwith DMF, CH,CN, and MeOH, succesivelyunderan argon atmosphereliberating a black filmy product from the electrodewith an evolution of H,. The productwasdried under vacuum affording a free-standingfilm about 20-40 pm in thickness. 3. Results and Discussion
Figure 1 showsthe IR spectraof the cathodicproductsand polyacetylenestandardspreparedwith Ziegler-Nattacatalyst.IR spectrumof the film sample(a) showstwo sharppeaksat 1009 and 742 cm-’ which are characteristicof 6,, out-of-planein tram- andc&conjugateddoublebonds,respectively.It shouldbe notedthat the spectrum(a) is quite different from that of the anodicproductreportedpreviously[3]. Fromthe two peakratio, the productconsistsof a pans-rich(transcontentis about60 %)
4000
3000
2000 Wavenumber
1000 (cm’)
Figure1. IR spectra of (a) as-prepared sample, (b) aq.HCl treated sample, (c)truns-polyacetylene, (d)cis-polyacetylene form of polyacetylene.Ramanspectrumof this sampleexcited with 785 run lasershowstwo intenseresonanceRamanpeaksat 1472 and 1079 cm-‘, which also suggeststhe product is polyacetyleneandthe degreeof polymerizationis morethti0. XRD analysisshowsthe product is amorphous.A low carbon content(about46 %) of the productsuggestspresence~of much contaminantsuch as metals and the electrolyte. Electrical conductivity of the film wasabout10 Scm‘]uponI, doping. SEM observation shows a cauliflower-like surface morphologytypical of electropolymerizedmaterials.After an HCl treatment,an absorptionat 3010 cm“ due to vc.Hof h’anspolyacetyleneisappears(figure 1 (b)) with liberationof a Cu ion. Theseresults suggestthat the polymerizationis proceededby an anionicmechanism with assistance of the metalion. 4. References
[I] C. W.Chien,Polyacetylene, Academic Press, 1984;H. Shimka@T. Masuda, K. T&da, in S.Pati (ed.),Supplement C2:TheChemistry of TripleBonded Functional Groups, Wiley,1994,p945. [2] S. -A. Chen,H. -.I. Shy,J. Polym.Sci.,-Polym.Chem.Ed., 23 (1981)2441. [3] K. Ohrnura, M. Kijima,H. Shirakawa, Synth.Met, 84(1997)417.
0379-6779199/$ - seefrontmatter0 1999Elsevier Science S.A. All rightsreserved. PII: SO379-6779(98)01 123-O