Molecular Ordering in Layer-by-Layer Polyelectrolyte Films Studied by Sum-Frequency Vibrational Spectroscopy: The Effects of Drying Procedures

Silva, Heurison S.; Uehara, Thiers M.; Bergamaski, Kleber; Miranda, Paulo B.

doi:10.1166/jnn.2008.125

Cited by 26 publications

(32 citation statements)

References 12 publications

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“…The samples dried under room conditions seem to be more homogeneous than those dried under vacuum or by nitrogen flow [28]. Silva et al [29] show that the hydrocarbon chains are more ordered using spontaneous water evaporation than those dried by nitrogen flow. They suggested that the spontaneous water evaporation reduces the effect of dragging by the drying front.…”

Section: Depositionmentioning

confidence: 99%

Infrared Spectroscopy of Anionic, Cationic, and Zwitterionic Surfactants

Viana

Silva

Pimentel

2012

Advances in Physical Chemistry

251

167

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This paper describes the ordering degree of anionic, cationic, and zwitterionic surfactants with the increase of their packing density on Ge substrate by using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy. This work shows new insights on the conformational order of sodium dodecyl sulfate (SDS), N-hexadecyl-N-N-dimethyl-3-ammonio-1-propanesulfonate (HPS), hexadecyl-trimethylammonium bromide (CTAB), and dodecyl trimethylammonium bromide (DTAB). DFT and semiempirical calculations are also performed in order to evaluate the effect of headgroup hydration and counterion. The CH 2 asymmetric and symmetric stretching bands for the SDS molecule show a shift of 1.7 and 0.9 cm −1 to higher frequencies as the packing density increases, while it is observed a shift of 2.6 and 2.7 cm −1 for the HPS molecule, respectively. The DTAB molecule shows a shift of 4.5 cm −1 to lower frequencies for both CH 2 asymmetric and symmetric stretching bands as the packing density increases, indicating the decrease of gauche conformations and the increase of all-trans conformations over the aliphatic chain.

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Section: Depositionmentioning

confidence: 99%

Infrared Spectroscopy of Anionic, Cationic, and Zwitterionic Surfactants

Viana

Silva

Pimentel

2012

Advances in Physical Chemistry

251

167

View full text Add to dashboard Cite

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“…After washing the substrate with an aqueous solution (usually of the same pH as the adsorption solution) in order to remove excess adsorbed material and to ensure that only one strongly adsorbed monolayer remains, the substrate is dried by N 2 flow. We have shown that this drying step promotes the inhomogeneity of the film in the micrometer scale [34], making it unfit for certain applications. The next step is immersing the substrate with the first adsorbed layer in an oppositely charged polyion solution.…”

Section: Layer-by-layer Thin Filmsmentioning

confidence: 99%

Probing the Molecular Ordering in Azopolymer Thin Films by Second-Order Nonlinear Optics

Silva¹,

Paz²,

Miranda³

2015

Advanced Electromagnetic Waves

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Second-harmonic generation (SHG), a second-order nonlinear optical technique, was used to investigate the molecular ordering of self-assembled layer-by-layer films of PAH, a cationic polyelectrolyte, and PS-119, an anionic polyelectrolyte containing photoisomerizable azo groups. Possible phase transitions in these multilayer films and their thermal stability were investigated by probing the SHG signal as a function of temperature and comparing the molecular order before and after thermal treatment. These studies were also performed with different pH values for the assembling solutions, a relevant parameter for polyelectrolyte adsorption. The results have shown that the films are not thermally stable, with the SHG signal nearly vanishing at a temperature of 150°C, in contrast to what is reported in the literature. SHG measurements have also confirmed that the films are isotropic in the plane of the samples, independent of their number of layers or the pH of assembling solutions. SHG signal before and after heating indicates that the SHG signal was considerably reduced at high temperatures, but after slow cooling it was recovered to almost the same value as before heating, showing that the thermal disorder is reversible. No phase transition was observed, since the SHG signal reduction was slow and gradual, without any sudden change that would characterize a glass transition. We demonstrate that the SHG technique provides information on the film arrangement at the microscopic level which could be difficult to get with traditional techniques.

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“…Considering this throughput limitation, a few alternative methods such as spray-assisted LbL assembly and spin-assisted LbL assembly have been suggested toward developing more rapid and straightforward processing. [5][6][7] In particular, the spinassisted LbL assembly using a highly applied shear force has been extensively investigated due to its advantages in alleviating surface roughness and interpenetration, as compared to the dipping-based LbL assembly. [7][8][9] Another notable aspect of the LbL self-assembly is that it usually leads to a linear growth in film thickness as exemplified in the case of many strongly charged polyelectrolyte multilayer systems.…”

Section: Introductionmentioning

confidence: 99%

Spin-Assembled Layer-by-Layer Films of Weakly Charged Polyelectrolyte Multilayer

Lee¹

2009

jnn

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We investigate the effect of film deposition methods on the film properties of layer-by-layer assembled polyelectrolyte multilayers. Multilayered structures of linear polyethylenimine (LPEI) and poly(acrylic acid) (PAA) are prepared by using conventional dipping-based assembly as well as spin-assisted assembly. While the polyelectrolyte interpenetration by the diffusion motion of LPEI species is allowed in dipping-based assembly, an instantaneously and kinetically frozen phase of the film deposition is obtainable from spin-assisted assembly. Being kept from the interdiffusion of LPEI, a stratified internal structure is expected in the spin-assisted assembly, which is completely contrasted to the intermixed phase in the dipping-based assembly. The ability to control the inner structure of the multilayered film enables us to manipulate the physical properties or chemical activity of the functionalized thin films. We also demonstrate that the control over the strength of polyelectrolyte interdiffusion on a very top surface can be utilized for a quantitative manipulation on the degree of macromolecular self-assembly of nanomaterials.

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Molecular Ordering in Layer-by-Layer Polyelectrolyte Films Studied by Sum-Frequency Vibrational Spectroscopy: The Effects of Drying Procedures

Cited by 26 publications

References 12 publications

Infrared Spectroscopy of Anionic, Cationic, and Zwitterionic Surfactants

Infrared Spectroscopy of Anionic, Cationic, and Zwitterionic Surfactants

Probing the Molecular Ordering in Azopolymer Thin Films by Second-Order Nonlinear Optics

Spin-Assembled Layer-by-Layer Films of Weakly Charged Polyelectrolyte Multilayer

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