scholarly journals Effects of Molecular Chain Length on the Contact Line Movement in Water/n-Alkane/Solid Systems

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2081
Author(s):  
Wenxiu Zheng ◽  
Chengzhen Sun ◽  
Boyao Wen ◽  
Bofeng Bai ◽  
Eric Lichtfouse
Keyword(s):  
Chain Length ◽  
Solid Surface ◽  
Contact Line ◽  
Molecular Chain ◽  
Dynamics Simulation ◽  
Jump Frequency ◽  
Molecular Kinetic Theory ◽  
Three Phase ◽  
Chain Lengths ◽  
Line Movement

The movement of the contact line in liquid-liquid-solid systems is a major phenomenon in natural and industrial processes. In particular, n-alkanes are widely occurring in the oil, soil pollution, and chemical industries, yet there is little knowledge on the effects of molecular chain length on the contact line movement. Here, we studied the effects of molecular chain length on the contact line movement in water/n-alkane/solid systems with different surface wettabilities. We used n-heptane (C7), n-decane (C10), and n-hexadecane (C16) as alkanes and α-quartz as the solid surface. We calculated the time-variation contact line moving velocity and also analyzed the jump frequency and the mean distance of the molecular displacement occurring within the contact line zone by molecular-kinetic theory. Molecular dynamics simulation results show that the contact line velocity decreases with increasing the chain length, originally caused by the decreasing the jump frequency and mean distance. These variations with the molecular chain length are related to the more torsions and deformations of the molecules with a longer chain length. In addition, the moving mechanism of the contact line on the same solid surface does not change at different molecular chain lengths, implying that the moving mechanism mainly depends on the three-phase wettability.

Effects of Free Surface Evaporation on Water Nano-Droplet Wetting Kinetics: A Molecular Dynamics Study

2013 ◽  
Author(s):  
Gui Lu ◽  
Yuan-Yuan Duan ◽  
Xiao-Dong Wang
Keyword(s):  
Molecular Dynamics ◽  
Free Surface ◽  
Contact Line ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Dynamic Wetting ◽  
Surface Evaporation ◽  
Molecular Kinetic Theory ◽  
Line Region ◽  
Wetting Kinetics

The dynamic wetting of water nano-droplet with evaporation on the heated gold substrate was examined using molecular dynamics simulation. Various substrate and droplet pre-heated temperatures were calculated to obtained different evaporating rates. Water molecules attachment-detachment details were traced near the contact line region to show the microscopic details and evidences for the spreading-evaporating droplet. The increasing substrate temperature greatly affected the dynamic wetting process, while the initial temperature of water droplet had very limited effects. The effects of free surface evaporation on wetting kinetics for both hydrophobic and hydrophilic substrates were examined. The radius versus time curves agree well with the Molecular kinetic theory (MKT) for spreading without evaporation and deviate from the MKT for the spreading with evaporation. The enhancement on wetting kinetics due to evaporation can be attributed to the reducing of liquid-vapor surface tension and the strengthening in water molecules transport in contact line region and bulk droplet.

Properties of Cotton Fabrics Crosslinked with Different Molecular Chain Lengths of Aldehyde Agents

1992 ◽  
Vol 62 (9) ◽  
pp. 547-551 ◽  
Author(s):  
Tsang-Yuh Liang ◽  
Jenn-Yann Hwang ◽  
Der-Shiann Ju ◽  
Cheng-Chi Chen
Keyword(s):  
Activation Energy ◽  
Chain Length ◽  
Cotton Fabric ◽  
Crosslinking Agent ◽  
Cotton Fabrics ◽  
Molecular Chain ◽  
Diffusion Resistance ◽  
Adsorption Time ◽  
Untreated Cotton ◽  
Chain Lengths

Adsorption time curves from finite baths have been studied for untreated cotton fabric and cottons treated with differing molecular chain lengths of aldehydes (formaldehyde and glutaraldehyde). Crosslinking reduced the rate constant, structural diffusion resistance constant, and equilibrium adsorption of dyeing. Additionally, these data decreased with increasing agent concentration and with increasing molecular chain length of the crosslinking agent. The dyeing activation energy of the glutaraldehyde treated fabric was lower than that of the formaldehyde treated fabric.

scholarly journals Mechanism of Contact Line Movement of a Droplet Spreading Over a Solid Surface

2016 ◽  
Vol 91 ◽  
pp. 01026
Author(s):  
Dmitry V. Feoktistov ◽  
Evgeniya G. Orlova ◽  
Anastasia G. Islamova
Keyword(s):  
Solid Surface ◽  
Contact Line ◽  
Droplet Spreading ◽  
Line Movement

Nanostructures Length Effect on Phase Transition Phenomena of Ultra-Thin Liquid Film From a Nanostructured Surface: A Molecular Dynamics Study

2011 ◽  
Author(s):  
A. K. M. M. Morshed ◽  
T. C. Paul ◽  
Jamil A. Khan
Keyword(s):  
Molecular Dynamics ◽  
Film Thickness ◽  
Liquid Film ◽  
Solid Surface ◽  
Thin Liquid Film ◽  
Liquid Argon ◽  
Liquid Film Thickness ◽  
Dynamics Simulation ◽  
Phase System ◽  
Three Phase

A molecular dynamics simulation has been employed to investigate the boiling phenomena of few molecular-layer thin liquid-film adsorbed on a nanoscale roughened solid surface. The molecular system comprises of three phase system: solid platinum wall, liquid argon and argon vapor. A few layer of liquid argon has been placed on the nanoposts decorated solid surface where nanoposts ensemble surface roughness. Nanoposts height has been varied keeping liquid film thickness constant to capture three scenario: (i) Liquid-film thickness is higher than the height of the nanoposts (ii) Liquid-film and nanoposts are of same height (iii) Liquid-film thickness is less than the height of the nanoposts. Rest of the simulation box space has been filled with argon vapor. The simulation starts from the equilibrium three phase system and then suddenly the wall is heated to a higher temperature which resembles an ultra fast laser heating. Two different jump temperatures has been selected: one is a few degrees above the boiling point to initiate normal evaporation and the other one is far above the critical point temperature to initiate explosive boiling. Simulation results indicate nanostructures play significant role in both the cases. Argon responds very quickly in the nanoposts decorated surface and evaporation rate increases with the nanoposts height. Different boiling behavior has been observed for the nanoposts decorated surface.

Effect of Nano-Scale Steps on the Microscopic Dynamic Contact Angle

2009 ◽  
Author(s):  
Junpei Doi ◽  
Takahiro Ito ◽  
Akira Hibi ◽  
Yutaka Kukita
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Solid Surface ◽  
Contact Line ◽  
Dynamic Contact ◽  
Immiscible Fluids ◽  
Step Edge ◽  
Dynamics Simulation ◽  
Step Height ◽  
Interaction Range

The motion of the contact line on a solid surface is strongly related with the contact angle there. In these days the relation between them has been revealed with the aid of molecular dynamics techniques; however, most of the studies on such phenomena have been made by assuming the solid surface to be molecularly planer and homogeneous, which condition is not necessarily satisfied in general industries. In this study, we conducted molecular dynamics simulation to investigate the behavior of dynamic contact line with a solid surface accompanied by steps parallel to the contact line. We applied a Couette flow geometry, where two immiscible fluids are confined between two parallel walls, one of which has the steps and is forced to move in the direction normal to the contact line. The behavior of the contact line and the variation in the contact angle were investigated by changing the height of the step from α0 to 4α0 where α0 is the lattice constant of the wall structure. It is shown that in case of the step height identical to α0, the contact line is temporary captured on the edge of the step. On the other hand with higher step the contact line is almost completely pinned on the step edge. The change in the contact angle by the pinning of the contact line on the step edge can be estimated by the macroscopic model as far as the step height is larger than the interaction range between molecules.

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