Effects of confinement on freezing and melting

Alba‐Simionesco, Christiane; Coasne, Benoît; Dosseh, Gilberte; Dudziak, G.; Gubbins, Keith E.; Radhakrishnan, Ravi; Śliwińska-Bartkowiak, Małgorzata

doi:10.1088/0953-8984/18/6/r01

Cited by 784 publications

(875 citation statements)

References 383 publications

(696 reference statements)

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“…At smaller separations the fluid enters a glassy state and the results are not reversible on any accessible time scales. Similar glass transitions have been observed in surface force apparatus (SFA) experiments [90,93,94] and simulations [69,78,[95][96][97].…”

Section: Simulation Methodssupporting

confidence: 80%

Capillary adhesion at the nanometer scale

Cheng

Robbins

2014

Phys. Rev. E

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Molecular dynamics simulations are used to study the capillary adhesion from a nonvolatile liquid meniscus between a spherical tip and a flat substrate. The atomic structure of the tip, the tip radius, the contact angles of the liquid on the two surfaces, and the volume of the liquid bridge are varied. The capillary force between the tip and substrate is calculated as a function of their separation h. The force agrees with continuum predictions based on macroscopic theory for h down to ∼5 to 10 nm. At smaller h, the force tends to be less attractive than predicted and has strong oscillations. This oscillatory component of the capillary force is completely missed in the macroscopic theory, which only includes contributions from the surface tension around the circumference of the meniscus and the pressure difference over the cross section of the meniscus. The oscillation is found to be due to molecular layering of the liquid confined in the narrow gap between the tip and substrate. This effect is most pronounced for large tip radii and/or smooth surfaces. The other two components considered by the macroscopic theory are also identified. The surface tension term, as well as the meniscus shape, is accurately described by the macroscopic theory for h down to ∼1 nm, but the capillary pressure term is always more positive than the corresponding continuum result. This shift in the capillary pressure reduces the average adhesion by a factor as large as 2 from its continuum value and is found to be due to an anisotropy in the pressure tensor. The component in the plane of the substrate is consistent with the capillary pressure predicted by the macroscopic theory (i.e., the Young-Laplace equation), but the normal pressure that determines the capillary force is always more positive than the continuum counterpart.

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Section: Simulation Methodssupporting

confidence: 80%

Capillary adhesion at the nanometer scale

Cheng

Robbins

2014

Phys. Rev. E

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“…A large array of nonbulklike phase behaviors have been observed and previously reviewed for various confined systems [45]. The measurements presented here may not be able to distinguish between a liquid and possible phase states that exist only in confined films.…”

Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 86%

Density and Phase State of a Confined Nonpolar Fluid

Kienle

Kuhl

2016

Phys. Rev. Lett.

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Measurements of the mean refractive index of a spherelike nonpolar fluid, octamethytetracylclosiloxane (OMCTS), confined between mica sheets, demonstrate direct and conclusive experimental evidence of the absence of a first-order liquid-to-solid phase transition in the fluid when confined, which has been suggested to occur from previous experimental and simulation results. The results also show that the density remains constant throughout confinement, and that the fluid is incompressible. This, along with the observation of very large increases (many orders of magnitude) in viscosity during confinement from the literature, demonstrate that the molecular motion is limited by the confining wall and not the molecular packing. In addition, the recently developed refractive index profile correction method, which enables the structural perturbation inherent at a solid-liquid interface and that of a liquid in confinement to be determined independently, was used to show that there was no measurable excess or depleted mass of OMCTS near the mica surface in bulk films or confined films of only two molecular layers.

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“…Several reviews have been written that discuss these issues in greater detail. [39][40][41][42] Although the general observation is that the glass transition of thin films is depressed, reports of the magnitude of the depression depend on the measurement technique as well as the details of the sample. For example, in cases of very strong interactions between the polymer and the sub-strate, increases in T g with decreasing film thickness have been reported.…”

Section: Introductionmentioning

confidence: 99%

Calorimetric glass transition temperature and absolute heat capacity of polystyrene ultrathin films

Koh

McKenna

Simon

2006

J Polym Sci B Polym Phys

114

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ABSTRACT:The absolute heat capacity and glass transition temperature (T g ) of unsupported ultrathin films were measured with differential scanning calorimetry with the step-scan method in an effort to further examine the thermodynamic behavior of glass-forming materials on the nanoscale. Films were stacked in layers with multiple preparation methods. The absolute heat capacity in both the glass and liquid states decreased with decreasing film thickness, and T g also decreased with decreasing film thickness. The magnitude of the T g depression was closer to that observed for films supported on rigid substrates than that observed for freely standing films. The stacked thin films regained bulk behavior after the application of pressure at a high temperature. The effects of various preparation methods were examined, including the use of polyisobutylene as an interleaving layer between the polystyrene films.

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Effects of confinement on freezing and melting

Cited by 784 publications

References 383 publications

Capillary adhesion at the nanometer scale

Capillary adhesion at the nanometer scale

Density and Phase State of a Confined Nonpolar Fluid

Calorimetric glass transition temperature and absolute heat capacity of polystyrene ultrathin films

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