Main and tilt transition in octadecylamine monolayers

Albrecht, O.; Matsuda, Hiro; Eguchi, Ken

doi:10.1016/j.colsurfa.2006.02.044

Cited by 20 publications

(26 citation statements)

References 19 publications

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“…More importantly, the shift of the LE-LC phase transition to smaller temperatures when the molecular heads carry an ion is in qualitative agreement with the experimental observations of fatty acid monolayer with ionic head groups [45]. We also calculated two isotherms at T = 1.5 and T = 0.5 for two system sizes N = 144 and N = 256 and found that their behavior looks very similar to the experimental isotherms [45,64,65]. From these isotherms we calculated the variation ranges of the monolayer's area compression modulus and encountered that they are consistent with the experimental values reported in Refs.…”

Section: Discussionsupporting

confidence: 85%

“…These isotherms correspond to a monolayer with ionic molecular heads and were calculated for two system sizes, one with 144 (•) and the other with 256 (•) molecules. Their behavior looks very similar to the experimental isotherms: as pressure decreases the area per molecule increases and the higher the temperature the larger the area per molecule [45,64,65]. Note that at these two temperatures there appears to be no signature of a Surface-pressure-versus-area-per-molecule isotherms for a monolayer with ionic molecular heads for systems with 144 and 256 molecules at T * = 0.5 and T * = 1.5.…”

Section: Isotherms and Compressibility Modulussupporting

confidence: 69%

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Phase behavior of Langmuir monolayers with ionic molecular heads: Molecular simulations

González-Castro

Ramı́rez-Santiago

2015

Phys. Rev. E

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We carried out Monte Carlo simulations in the N,Π,T ensemble of a Langmuir monolayer coarse-grained molecular model. Considering that the hydrophilic groups can be ionized by modulating acid-base interactions, here we study the phase behavior of a model that incorporates the short-range steric and long-range ionic interactions. The simulations were carried out in the reduced temperature range 0.1≤T*<4.0, where there is a competition of these interactions. Different order parameters were calculated and analyzed for several values of the reduced surface pressure in the interval, 1≤Π*≤40. For most of the surface pressures two directions of molecular tilt were found: (i) towards the nearest neighbor (NN) at low temperatures, T*<0.7, and most of the values of Π* and (ii) towards next-nearest neighbors (NNN) in the temperature interval 0.7≤T*<1.1 for Π*<25. We also found the coexistence of the NN and NNN at intermediate temperatures and Π*>25. A low-temperature reentrant disorder-order-disorder transition in the positions of the molecular heads and in the collective tilt of the tails was found for all the surface pressure values. It was also found that the molecular tails arranged forming "rotating patterns" in the temperature interval, 0.5

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Section: Discussionsupporting

confidence: 85%

Section: Isotherms and Compressibility Modulussupporting

confidence: 69%

Phase behavior of Langmuir monolayers with ionic molecular heads: Molecular simulations

González-Castro

Ramı́rez-Santiago

2015

Phys. Rev. E

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“…Therefore, 80 nm silica nanoparticles are coated with a short-chain aminosilane (APTES) with the same terminating functional group as the oil-soluble surfactant octadecylamine (ODA) . At mildly acidic conditions, the particles exhibit a significant positive surface charge with good dispersibility in water (Figure S1) while the partially positively charged amine head groups of the adsorbed ODA molecules act as a weak base (p K a ODA: 10.65), thereby alkalifying the pH of the interfacial region with negligible solubility in the water phase. , An overview of the chosen methodology is given in Figure .…”

Section: Resultsmentioning

confidence: 99%

Reversible Adsorption of Nanoparticles at Surfactant-Laden Liquid–Liquid Interfaces

et al. 2019

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In this study, we show that hydrophilic nanoparticles can readily desorb from liquid−liquid interfaces in the presence of surfactants that do not change the wettability of the particles. Our observations are based on a simple theoretical approach to assess the number of adsorbed particles at the surfactant-laden liquid−liquid interface. We test this approach by studying the interfacial self-assembly of equally charged particles and lipids dissolved in separate immiscible phases. Hence, we investigate the interfacial adsorption of aminated silica particles (80 nm) and octadecylamine to the decane/water interface by interfacial tension measurements, which are supplemented by interfacial rheology of the adsorbed interfacial films, scanning electron microscopy images of Langmuir−Blodgett films, and measurements of the three-phase contact angle of the particle surface in the presence of surfactants. The measurements show that particles adsorb at the surfactant-laden interface at all investigated surfactant concentrations and compete with the surfactants for interfacial coverage. Additionally, the wettability of the hydrophilic particles does not change in the presence of the lipids, except for the highest investigated lipid concentration. Comparing the adsorption energies of one particle and of the lipids as a function of the particle contact angle provides an estimate of the tendency for interfacial adsorption of particles from which the particle coverage can be assessed. Based on these findings, equally charged particles and lipids show a competitive behavior at the interface determined by the bulk surfactant concentration and the attachment energies of the particles at the interface. This leads to a simple mechanistic model demonstrating that particles can readily desorb from the interface due to direct displacement by surfactants, which are loosely adsorbed at the oil-facing particle side. This mechanism critically lowers the otherwise high interfacial energy barrier against particle desorption, which otherwise would lead to virtually irreversible particle attachment at the interface.

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“…Positive and high V values for PIM-EA-TB(H 2 ) suggest that the dipole moments in the film should mainly point to the normal to the water surface. Moreover, partial protonation of the amine groups of the Tröger's base at the air-water interface can be expected due to the acidification of the water subphase by the presence of CO 2 in the -TB(H 2 ) PIM-TMN-Trip atmosphere as it has been reported for other amines[15,16]. For PIM-1 and PIM-TMN-Trip films there is no contribution from the double-layer to the surface potential and the low V values observed for PIM-1 would be a consequence of the contorted 3D structure of the polymeric chains that have their dipole moments randomly oriented.Finally, the slightly negative V values obtained for PIM-TMN-Trip would indicate that   is low for the films of this polymer.…”

mentioning

confidence: 79%

The fabrication of ultrathin films and their gas separation performance from polymers of intrinsic microporosity with two-dimensional (2D) and three-dimensional (3D) chain conformations

Benito

Vidal

Sánchez‐Laínez

et al. 2019

Journal of Colloid and Interface Science

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The fabrication of ultrathin films and their gas separation performance from polymers of intrinsic microporosity with two-dimensional (2D) and three-dimensional (3D) chain conformations, Journal of Colloid and Interface Science (2018), doi: https://doi. AbstractThe expansion of the use of polymeric membranes in gas separation requires the development of membranes based on new polymers with improved properties and their assessment under real operating conditions. In particular, the fabrication of ultrathin films of high performance polymers that can be used as the selective layer in composite membranes will allow large reductions in the amount of the expensive polymer used and, hence, the cost of membrane fabrication.In this contribution, two polymers of intrinsic microporosity (PIMs) with very different chain configurations (two-dimensional, 2D, chains or conventional contorted threedimensional, 3D, conformation) have been compared in their ability to form ultrathin films, showing the relevance of polymer design to obtain compact and defect-free films.Monolayers of the 2D polymer PIM-TMN-Trip can be efficiently deposited onto poly[1-(trimethylsilyl)-1-propyne] (PTMSP) to obtain composite membranes with a CO 2 /N 2 selectivity similar to that of the corresponding thick membranes of the same PIM using only a small fraction of the selective polymer (less than 0.1%).

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Main and tilt transition in octadecylamine monolayers

Cited by 20 publications

References 19 publications

Phase behavior of Langmuir monolayers with ionic molecular heads: Molecular simulations

Phase behavior of Langmuir monolayers with ionic molecular heads: Molecular simulations

Reversible Adsorption of Nanoparticles at Surfactant-Laden Liquid–Liquid Interfaces

The fabrication of ultrathin films and their gas separation performance from polymers of intrinsic microporosity with two-dimensional (2D) and three-dimensional (3D) chain conformations

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