Surface Supercooling and Stability ofn-Alkane Films

Abstract

The surface tension of n-octadecane was studied in the vicinity of the bulk melting point using both the maximum bubble pressure and Wilhelmy plate methods. The bubble surfaces were found to be supercooled below the surface freezing point. The onset of surface freezing is indicated by a sharp drop in surface tension at a constant temperature. This transition is accompanied by an increased film stability resulting in longer bubble lifetimes at the liquid surface. Variations in bubble lifetime reflect changes in the interfacial mechanical properties of the film from liquidlike to solidlike.

Surface tension of normal and branched alkanes

“…We present results for the surface tension of all five chain lengths as a function of temperature using Ewald summation for both electrostatic and dispersion interactions in figure 3 for the OPLS and Smith force fields. Experimental data [22,24] are also plotted where available. Comparing the two sets of results, we see that the behaviour observed for hexane and decane persist for longer chains, with the Smith force field having a consistently higher surface tension than the corresponding state point for the OPLS force field.…”

“…Numerical investigations of the interfacial properties of n-alkanes appear to have begun with the work of Harris [23], who used a united-atom version of the OPLS force field to calculate the liquid-vapour interfacial structure and surface tension. More recently, investigators have focused on the surface tensions not only of pure components but also of binary and ternary mixtures of n-alkanes, using a variety of experimental techniques [24][25][26][27][28]. More recent computational studies include the work of Freitas et al who used free-energy analyses to determine the surface tension of a large number of organic liquids, including n-alkanes [29], and Fu et al who used perturbed-chain statistical associating fluid theory and renormalization-group methods for chains up to tetracosane (C 24 H 50 ) [30].…”

Demixing Transition in a Quasi-Two-Dimensional Surface-Frozen Layer

“…Although continuous transitions are predicted by some well-known 2D models, e.g., the Ising model [12], first-order 2D transitions are also possible theoretically, e.g., the XY model for He films and planar magnets and the grain-boundary-mediated melting model [13]. The abruptness of the present thin/thick transition seems to indicate a first-order transition, the same as that of the SF effect [2,14]. Note that T f and T s above are closer to T f 60 C of pure hydrated C 18 OH than to T f 84 C of pure hydrated C 28 OH [1], in line with the low bulk concentration of C 28 OH, 0:2.…”

Bubble vortex at surfaces of evaporating liquids

“…In contrast, bubble coalescence in pure liquids is instant at vapor coexistence in which case the slip coefficient equals unity. The only exemption from this rule is systems with surface freezing [27].…”