“…UV spectra taken in the parallel and perpendicular polarization with respect to dipping direction essentially agreed with each other for both films, indicating that no preferential orientation in the backbone was attained in these LB films. We have observed a preferred orientation for C 18 APS LB films in the direction of the dipping direction. − This main chain orientation in the C 18 APS films is probablyattained by a flow effect on the water surface . We will discuss this point in the last part of section 3.3.…”
Section: Resultsmentioning
confidence: 80%
“…With increasing pH, the absorption band exhibited hypsochromic shifts. The band shifts should reflect changes in the conformational state of the Si backbone of APS. − Absorbance at the peak wavelength decreased in acidic regions, indicating that amounts of transferred APS are reduced. 6 Maximum wavelengths of the σ−σ* band of APS in the polyion complex LB monolayers (a) and absorbance at these wavelengths (b) as a function of subphase pH.…”
Section: Resultsmentioning
confidence: 99%
“…Changes in the optical properties indicated above should be closely coupled with changes in the dissociation state of the carboxylic acid moiety of the C 19 COOH monolayer on the water surface. On the basis of the above spectroscopic observations, − the following model which is schematically drawn in Figure can be assumed. The conformational state of electrostatically absorbed APS is influenced by the changes in the two-dimensional density of anionic charge, namely the protonation state of the carboxyl head group, beneath the C 19 COO(H) monolayer.…”
Section: Resultsmentioning
confidence: 99%
“…On the Orientation of the APS Main Chain. The LB deposition procedure of the vertical dipping frequently induces an in-plane main chain orientation of polysilane materials in LB films. − Figure depicts the polarized UV−visible absorption spectra of two-layered LB films of C 19 COO(H)/APS deposited at pH 8.0 (a) and five-layered 2C 12 SO 3 - /APS (b). UV spectra taken in the parallel and perpendicular polarization with respect to dipping direction essentially agreed with each other for both films, indicating that no preferential orientation in the backbone was attained in these LB films.…”
Section: Resultsmentioning
confidence: 99%
“…These optical properties are anticipated to shed light on the main chain orientation and conformational states. We have recently developed a series of ammonium-containing polysilanes. − The materials having a long alkylammonium moiety, like other chemically functionalized polysilanes, − are amphiphilic and found to be successfully assembled as multilayers by the ordinary LB technique. − On the other hand, a compound with a trimethylammonium group (APS, Chart ) becomes water-soluble, , and this material would be used as the polyelectrolyte component in the polyion complex LB films.…”
Monolayers of anionic amphiphiles, arachidic acid
(C19COOH) and a double long chain
sulfonic acid derivative (2C12SO3Na),
were spread on the water subphase containing an ammonium-containing polysilane (APS), and Langmuir−Blodgett (LB) films from
these polyion complex monolayers
were prepared. Single layer deposition of these polyion complex
monolayers was successfully achieved
onto a hydrophilic substrate under all conditions examined, but
multilayers could be prepared under
limited conditions in the Z-type mode. The UV absorption spectra
of the transferred C19COO(H)/APS
monolayers indicated that the conformational state of APS in the films
are dependent on the subphase
pH. The absorbance of the transferred LB films confirmed that the
APS is incorporated monomolecularly
on the lifting process. Polarized UV absorption spectra revealed
no preferential orientation of the APS
backbone in the LB films. The multilayers formed in the Z-type
deposition were eventually inverted to
stacked bilayer structure (Y-type layers) after aging and successive
annealing, as proven by the small
angle X-ray reflectometry. LB films composed of
2C12SO3
-/APS possessed a
more refined layer structure
with a more smooth surface than those of
C19COO(H)/APS, probably due to a better
dimensional matching
of the APS unit and the cross section of the amphiphile. Finally,
structural features of the C19COO(H)/APS polyion complex LB film were discussed in comparison with those of a
homologous amphiphilic
material reported previously (Seki et al. Macromolecules
1995, 28, 5609).
“…UV spectra taken in the parallel and perpendicular polarization with respect to dipping direction essentially agreed with each other for both films, indicating that no preferential orientation in the backbone was attained in these LB films. We have observed a preferred orientation for C 18 APS LB films in the direction of the dipping direction. − This main chain orientation in the C 18 APS films is probablyattained by a flow effect on the water surface . We will discuss this point in the last part of section 3.3.…”
Section: Resultsmentioning
confidence: 80%
“…With increasing pH, the absorption band exhibited hypsochromic shifts. The band shifts should reflect changes in the conformational state of the Si backbone of APS. − Absorbance at the peak wavelength decreased in acidic regions, indicating that amounts of transferred APS are reduced. 6 Maximum wavelengths of the σ−σ* band of APS in the polyion complex LB monolayers (a) and absorbance at these wavelengths (b) as a function of subphase pH.…”
Section: Resultsmentioning
confidence: 99%
“…Changes in the optical properties indicated above should be closely coupled with changes in the dissociation state of the carboxylic acid moiety of the C 19 COOH monolayer on the water surface. On the basis of the above spectroscopic observations, − the following model which is schematically drawn in Figure can be assumed. The conformational state of electrostatically absorbed APS is influenced by the changes in the two-dimensional density of anionic charge, namely the protonation state of the carboxyl head group, beneath the C 19 COO(H) monolayer.…”
Section: Resultsmentioning
confidence: 99%
“…On the Orientation of the APS Main Chain. The LB deposition procedure of the vertical dipping frequently induces an in-plane main chain orientation of polysilane materials in LB films. − Figure depicts the polarized UV−visible absorption spectra of two-layered LB films of C 19 COO(H)/APS deposited at pH 8.0 (a) and five-layered 2C 12 SO 3 - /APS (b). UV spectra taken in the parallel and perpendicular polarization with respect to dipping direction essentially agreed with each other for both films, indicating that no preferential orientation in the backbone was attained in these LB films.…”
Section: Resultsmentioning
confidence: 99%
“…These optical properties are anticipated to shed light on the main chain orientation and conformational states. We have recently developed a series of ammonium-containing polysilanes. − The materials having a long alkylammonium moiety, like other chemically functionalized polysilanes, − are amphiphilic and found to be successfully assembled as multilayers by the ordinary LB technique. − On the other hand, a compound with a trimethylammonium group (APS, Chart ) becomes water-soluble, , and this material would be used as the polyelectrolyte component in the polyion complex LB films.…”
Monolayers of anionic amphiphiles, arachidic acid
(C19COOH) and a double long chain
sulfonic acid derivative (2C12SO3Na),
were spread on the water subphase containing an ammonium-containing polysilane (APS), and Langmuir−Blodgett (LB) films from
these polyion complex monolayers
were prepared. Single layer deposition of these polyion complex
monolayers was successfully achieved
onto a hydrophilic substrate under all conditions examined, but
multilayers could be prepared under
limited conditions in the Z-type mode. The UV absorption spectra
of the transferred C19COO(H)/APS
monolayers indicated that the conformational state of APS in the films
are dependent on the subphase
pH. The absorbance of the transferred LB films confirmed that the
APS is incorporated monomolecularly
on the lifting process. Polarized UV absorption spectra revealed
no preferential orientation of the APS
backbone in the LB films. The multilayers formed in the Z-type
deposition were eventually inverted to
stacked bilayer structure (Y-type layers) after aging and successive
annealing, as proven by the small
angle X-ray reflectometry. LB films composed of
2C12SO3
-/APS possessed a
more refined layer structure
with a more smooth surface than those of
C19COO(H)/APS, probably due to a better
dimensional matching
of the APS unit and the cross section of the amphiphile. Finally,
structural features of the C19COO(H)/APS polyion complex LB film were discussed in comparison with those of a
homologous amphiphilic
material reported previously (Seki et al. Macromolecules
1995, 28, 5609).
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