“…Sigmund and co-workers reported a rodlike image of 3-hexadecylpyrrole and 3-decylpyrrole LB monolayers obtained by scanning tunneling microscopy. The images suggest that the molecules lie flat on the surface, which agrees with our results 7f although we cannot ignore the possibility of the electron transfer through defects in the monolayers.…”
Section: Resultssupporting
confidence: 92%
“…Langmuir monolayers of alkyl-substituted monomers such as pyrrole, aniline, thiophene have been extensively studied in order to understand the packing structures and electronic properties after they were transferred to solid substrates . To date, however, there were no direct comparisons between the SA and LB monolayers that have structural similarities.…”
“…Sigmund and co-workers reported a rodlike image of 3-hexadecylpyrrole and 3-decylpyrrole LB monolayers obtained by scanning tunneling microscopy. The images suggest that the molecules lie flat on the surface, which agrees with our results 7f although we cannot ignore the possibility of the electron transfer through defects in the monolayers.…”
Section: Resultssupporting
confidence: 92%
“…Langmuir monolayers of alkyl-substituted monomers such as pyrrole, aniline, thiophene have been extensively studied in order to understand the packing structures and electronic properties after they were transferred to solid substrates . To date, however, there were no direct comparisons between the SA and LB monolayers that have structural similarities.…”
“…However, this polymeric thin layer is very stiff and when compressed to a small surface area it causes the swiveling of the Wilhelmy plate at small angles to the side: hence, for more accurate measurements in the collapse region a trough with two opposite moving barriers might be necessary . The cross-sectional area of the repeat unit extrapolated to zero lateral pressure is somewhat smaller than the typical value (of the order of 25 Å 2 ) expected for pyrroles. , 2 Isotherm corresponding to the first compression of a floating film of pAcBPY (on a water subphase at a temperature of 23 °C) spread from a diluted solution.…”
We have investigated the properties of thin films of a substituted polypyrrole synthesized via the chemical
oxidation of a chloroform solution of 5-acetamido-4,5,6,7-tetrahydro-2H-benzo[c]pyrrole. Repeated compressions of Langmuir films prepared by spreading a dilute chloroform/dimethyl sulfoxide solution of the
polymer at an air−water interface have established their long-term stability as floating monolayers.
Hysteresis experiments and surface potential measurements have indicated that while the stiff condensed
layer changes its structure upon the first compression, the size and distribution of floating domains remain
invariant under subsequent cycles of compression and decompression. An infrared spectroscopic investigation
was carried out for KBr mixed pellets of the material and for Langmuir−Blodgett (LB) films obtained by
depositing six monolayers of the polymer on ZnSe crystals. The presence of a broad bipolaron band both
in the transmission and in the attenuated total reflection (ATR) spectra indicates that in its pristine form
the polymer was already slightly doped, a hypothesis confirmed by preliminary two-probe measurements.
To better understand the nature of the organization of the deposited films we performed a linear dichroism
analysis of the polarized ATR spectra and found evidence that the polymeric chains are transferred in a
helical manner along the surface of the substrate.
“…This highly anisotropic conductivity arises due to the presence of insulating AA layers in between the polymer layers in the LB film. Honda's group 16,54 have reported a similar anisotropic conducting film prepared by polymerization of amphiphilic pyrrole derivative in its LB film. Their film had an alternating layered structure of a conducting polypyrrole layer and an insulating alkyl chain layer.…”
Langmuir-Blodgett (LB) films of the water-soluble dye phenosafranine (PS) have been prepared by its adsorption from aqueous dye solution to an arachidic acid (AA) monolayer at the air-water interface. Atomic force microscopy (AFM) images of the LB films revealed the effect of change in pH of deposition on the degree of complexation of AA with the PS dye. Well-defined circular islands and holes were observed which disappeared with the increase in pH. Polarized absorption studies indicated that the dye molecules are oriented uniaxially with their long axis titled at a constant angle to the surface normal of the LB film. Within the restricted geometry of the LB film, the PS dye was electropolymerized to form a two-dimensional film of poly(phenosafranine) sandwiched between arachidic acid layers. The film was characterized by IR spectroscopy, cyclic voltammetry, and AFM. X-ray diffraction studies reveal the presence of a layer structure in the AA-PS LB film before and after polymerization. The polymer film showed highly anisotropic electrical conductivity of ca. 10 orders of magnitude. This indicates the formation of two-dimensional polyPS layers between arachidic acid layers resulting in a layered heterostructure film having alternate conducting and insulating regions. Also, the conductivity of the polyPS prepared from LB film was found to be ∼2.5 times higher than the conductivity of polyPS prepared by solution polymerization method.
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