Scanning tunneling microscopy and X-ray photoelectron spectroscopy studies of borate-substituted polyaniline

Porter, T. L.; Dillingham, T. R.; Lee, C.Y.; Jones, Tabitha; Wheeler, B. L.; Caple, G.

doi:10.1016/0379-6779(91)91775-6

Cited by 13 publications

(2 citation statements)

References 20 publications

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“…In this regard, efforts have been made to increase the processibility using the various substituent groups (−CH 3 , −OCH 3 , −OC 2 H 5 , etc.) in the polymer backbone − (Figure a). Therefore, in recent years substituted polyanilines such as poly( o -anisidine) (POAS), , poly(methylaniline), ,, or poly( o -alkoxyaniline) 22 have been synthesized showing the change in electron localization, redox kinetic, with an excellent solubility and a small decrease in conductivity in comparison to the parent polyaniline.…”

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confidence: 99%

Investigation of Ultrathin Films of Processable Poly(o-anisidine) Conducting Polymer Obtained by the Langmuir−Blodgett Technique

1997

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Langmuir films of poly(o-anisidine) conducting polymer in its undoped (emeraldine base) and doped (emeraldine salt) forms have been obtained by the proper selection of subphase. π/A isotherms, quartz crystal microbalance, Brewster angle microscopic, and UV-vis-near IR spectroscopic measurements provided evidence concerning the effects of HCl doping on the polymer molecular organization as well as film properties. The analysis underlines that the presence of dopant induces structural and conformational changes on the polymer structure from the emeraldine base to emeraldine salt, so causing a different arrangement of the molecules at the air/water interface. Moreover, the emeraldine base form of poly(o-anisidine) Langmuir films evidenced less compressibility, as suggested by the presence of aggregates at high surface pressures, and a lower collapse surface pressure with respect to the emeraldine salt one. The investigation of the Langmuir film formation by the Brewster angle microscopy made it possible to support the previous experimental results and to image directly two (2D)-three (3D) dimensional transformations, which occurred by overcompressing beyond the limiting densities of close-packed 2D films, namely, collapse pressure. The recorded optical spectra revealed the development of polarons and bipolarons due to inclusion of the dopant in the polymer backbone and also provided an estimation of the poly(o-anisidine) bandgap.

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Section: Introductionmentioning

confidence: 99%

Investigation of Ultrathin Films of Processable Poly(o-anisidine) Conducting Polymer Obtained by the Langmuir−Blodgett Technique

1997

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“…Recent studies have shown that scanning tunneling microscopy (STM) and related methods are powerful tools to elucidate the structures and conformations of conducting polymers [2][3][4][5][6][7][8][9]. The electropolymerization growth process has also been investigated by STM [10][11][12][13].…”

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In situ STM tip-induced electropolymerization of poly(3-octylthiophene)

Zhou

Zhang

et al. 1998

Applied Physics A: Materials Science & Processing

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Poly(3-octylthiophene) has been grown on an indium-tin-oxide (ITO)-coated glass substrate by an STM tipinduced polymerization technique in which a high anodic bias is applied on the substrate. Molecular images of resultant polymer structures are obtained by a subsequent in situ STM study. We find that a three-dimensional nucleation and growth mechanism operates to deposit both nodular and helical polymer structures. Consideration of the helix diameters (range 25-70 Å) obtained points to the existence of both simple helices and superhelices. Initial nucleation occurs preferentially at the ITO grain boundaries, probably because of an altered electronic state from the segregation of dopants there.Since the discovery in 1977 [1] of the first conducting polymer, the doped polyacetylene (PA), many families of conducting polymers have been found. Among them, heterocyclic polymers based on pyrrole and thiophene have been intensively studied because of their relatively simple preparation, good chemical and thermal stability, high conductivity and potential applications in various fields. Even in the homopolymers, the macroscopic properties are governed by complex structure-property relationships relating to the linkage mode, stereoregularity and chain conformation in the polymer backbone.Recent studies have shown that scanning tunneling microscopy (STM) and related methods are powerful tools to elucidate the structures and conformations of conducting polymers [2-9]. The electropolymerization growth process has also been investigated by STM [10][11][12][13]. Early work by Yang et al. [2,3] showed the presence in doped polythiophene (PT) of helical structures with a diameter of 15 ± 3 Å and a pitch of 8 ± 1.5 Å; on polypyrrole, they found helical structures of diameter 18 Å and pitch 5 Å. Recently, another group reported the helix diameter of polythiophene to be in the range 9 − 15 ± 2 Å using a noncontact scanning probe microscopy technique [9]. These values are consistent with helices having repeat units per turn in the polymer backbone.For these unsubstituted polythiophene and polypyrrole, large helical structures of diameter 50-60 Å have also been * To whom all correspondences should be addressed observed [3]. It is thought that these structures are superhelices, in which helical polymer chains further coil on themselves to give a ternary structure. To the best of our knowledge, the largest 3-alkyl derivative reported is poly(3-methylthiophene) whose helices have been measured by STM with a diameter about 22 Å and height about 20 ± 3 Å [5].Atomistic simulations of the conformations of polythiophene, polypyrrole and their derivatives have indicated the formation of both anti-like and syn-like chain conformations and the existence of stable helical structures [14][15][16]. The calculated helix diameter agrees well with the values measured by STM and related methods.In this study, we have used the STM tip-induced eletropolymerization technique to polymerize 3-octylthiophene on ITO glass and subsequently study the polymeric...

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