Investigation of the saturated adsorption layer of 5-cyano-biphenyl and 5-cyano-terphenyl at the free water surface by Monte Carlo simulation

Jedlovszky, Pál; Partay, L.B.

doi:10.1016/j.molliq.2007.08.013

Cited by 9 publications

(6 citation statements)

References 59 publications

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“…A recent Monte Carlo (MC) simulation study on the 5CB and 5CT molecules at the air/water interface concluded that the properties of the adsorption layers of these two different molecules were rather similar to each other. 80 In summary, the difference of the surface density at which the gaseous-liquid condensed co-existence phase to the condensed phase transition for the 8CB, 5CB (between Regions I and II, as defined above) and 5CT monolayers can be understood through the difference of the stronger attractive forces of the terphenyl in the nCT molecules than that of the biphenyl groups in the nCB molecules. The molecular origin of the second phase transition, which is unique for the nCB molecules, has not been fully understood, even though it was thought to be related to possible water penetration into the nCB monolayers.…”

Section: Resultsmentioning

confidence: 99%

Water penetration/accommodation and phase behaviour of the neutral langmuir monolayer at the air/water interface probed with sum frequency generation vibrational spectroscopy (SFG-VS)

Zhang

Dong

Guo

et al. 2009

Phys. Chem. Chem. Phys.

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A strong and broad hydrogen bonded O-H band around 3520 cm(-1) is observed in the insoluble monolayer of the neutral liquid crystal molecules of 4''-n-pentyl-4-p-cyanobiphenyl (5CB) and 4''-n-octyl-4-p-cyanobiphenyl (8CB) throughout the whole surface density range, but not in the 4-pentyl-4'-cyanoterphenyl (5CT) monolayer, at the air/water interface. This novel spectral feature suggests the existence of an oriented water cluster species which has penetrated or accommodated into the Langmuir monolayer of the 8CB and 5CB molecules. This finding provided a molecular level mechanism for the stark difference in the phase behaviour between the CB and CT insoluble Langmuir monolayers at the air/water interface. It also calls for attention to the details of the specific water-surface interaction in mediating the structure and the phase behaviour of the molecular assemblies at the heterogeneous aqueous interfaces.

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Section: Resultsmentioning

confidence: 99%

Water penetration/accommodation and phase behaviour of the neutral langmuir monolayer at the air/water interface probed with sum frequency generation vibrational spectroscopy (SFG-VS)

Zhang

Dong

Guo

et al. 2009

Phys. Chem. Chem. Phys.

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“…The adsorption layer of several other, mostly grafted copolymers has also been the target of computer simulation investigations . Further, the adsorption layer of SDS − and other ionic, − zwitterionic, − and nonionic − surfactants has also been simulated in a number of times both at the free water surface ,,,,− ,− and at the liquid−liquid interface between water and various apolar liquids. − ,,,, However, in spite of the wealth of such studies, we are only aware of one single publication concerning computer simulation investigation of the mixed PEO−SDS system in the bulk phase of their aqueous solution, whereas, to the best of our knowledge, the mixed adsorption layer of PEO and SDS has never been investigated yet by means of computer simulation methods.…”

Section: Introductionmentioning

confidence: 99%

Competitive Adsorption of Surfactants and Polymers at the Free Water Surface. A Computer Simulation Study of the Sodium Dodecyl Sulfate−Poly(ethylene oxide) System

2011

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Competitive adsorption of a neutral amphiphilic polymer, namely poly(ethylene oxide) (PEO) and an ionic surfactant, i.e., sodium dodecyl sulfate (SDS), is investigated at the free water surface by computer simulation methods at 298 K. The sampled equilibrium configurations are analyzed in terms of the novel identification of the truly interfacial molecules (ITIM) method, by which the intrinsic surface of the aqueous phase (i.e., its real surface corrugated by the capillary waves) instead of an ideally flat surface approximating its macroscopic surface plane, can be taken into account. In the simulations, the surface density of SDS is gradually increased from zero up to saturation, and the structural, dynamical, and energetic aspects of the gradual squeezing out of the PEO chains from the surface are analyzed in detail. The obtained results reveal that this squeezing out occurs in a rather intricate way. Thus, in the presence of a moderate amount of SDS the majority of the PEO monomer units, forming long bulk phase loops in the absence of SDS, are attracted to the surface of the solution. This synergistic effect of SDS of moderate surface density on the adsorption of PEO is explained by two factors, namely by the electrostatic attraction between the ionic groups of the surfactant and the moderately polar monomer units of the polymer, and by the increase of the conformational entropy of the polymer chain in the presence of the surfactant. This latter effect, thought to be the dominant one among the above two factors, also implies the formation of similar polymer/surfactant complexes at the interface than what are known to exist in the bulk phase of the solution. Finally, in the presence of a large amount of SDS the more surface active surfactant molecules gradually replace the PEO monomer units at the interfacial positions, and squeezing out the PEO molecules from the surface in a monomer unit by monomer unit manner.

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“…The 5CB is one of the best known liquid crystalline materials. It is in the nematic phase between 22.5°C and 35.5°C 15,16 .…”

Section: Exprimental Section Materialsmentioning

confidence: 99%

Dielectric relaxation behavior of nematic liquid crystal cell using β-cyclodextrin as an alignment layer

Sahraoui

Abderrahmen²,

Mlika³

et al. 2016

Mediterr.J.Chem

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In the present investigation, we report the dielectric properties of a symmetric Nematic Liquid Crystal (NLC) cell using Beta Cyclodextrins (β-CD) as alignment layers. These layers were deposited onto Indium Tin Oxide (ITO) surface by thermal evaporation and then characterized using contact angle measurement. This revealed a hydrophilic character attributed to the presence of hydroxyl groups. Morphological study was carried out by Scanning Electronic Microscopy (SEM).The dynamic impedance study of the Liquid Crystal (LC) cell in a wide frequency range from 1mHz to 13MHz was reported. It was found that the β-CD alignment layer had a blocking effect on the NLC cell at a high frequency range. We also report the relaxation mechanism of NLC cell which is modeled by an appropriate equivalent circuit in order to understand the electrical properties of the liquid crystal cell and to investigate the processes taking place at different interfaces.

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Investigation of the saturated adsorption layer of 5-cyano-biphenyl and 5-cyano-terphenyl at the free water surface by Monte Carlo simulation

Cited by 9 publications

References 59 publications

Water penetration/accommodation and phase behaviour of the neutral langmuir monolayer at the air/water interface probed with sum frequency generation vibrational spectroscopy (SFG-VS)

Water penetration/accommodation and phase behaviour of the neutral langmuir monolayer at the air/water interface probed with sum frequency generation vibrational spectroscopy (SFG-VS)

Competitive Adsorption of Surfactants and Polymers at the Free Water Surface. A Computer Simulation Study of the Sodium Dodecyl Sulfate−Poly(ethylene oxide) System

Dielectric relaxation behavior of nematic liquid crystal cell using β-cyclodextrin as an alignment layer

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