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Molecular simulations of micellar assemblies under temperature and pressure extremes.

机译：极端温度和压力下的胶束装配体的分子模拟。

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摘要

Surfactant micelles potentially face extreme temperatures and pressures in a range of oil production processes. Technologically, pressure-dependent micelle assembly can impact surfactant efficacy in applications such as the dispersant remediation of deep-sea oil spills where the pressure dramatically varies from the sea floor to the water surface. The pressure dependence of hydrophobic species transfer thermodynamics is mirrored as maxima in the critical micelle concentrations of nonionic, ionic and polymeric surfactants, with accompanying changes in the sign of the surfactant volume of assembly from positive to negative with increasing pressure.;In this dissertation, we report on the pressure effects on the volumes of assembly for ionic and nonionic surfactants using molecular dynamic simulation. These simulations verify that changes in the sign of the volume of micellization associated with pressure reentrant assembly result from the enhanced compressibility of surfactants in assemblies compared to monomers, which can be largely attributed to the hydrocarbon core of the micelles. The headgroup and tailgroup contributions to the volumes of micellization are analyzed through Kirkwood-Buff theory based on the proximal distribution of water.;Next, we investigate the impact of pressure on the uptake of argon, a model nonpolar gas, by anionic and nonionic surfactant micelles. The micelle/solute interactions are quantified via molecularly detailed potentials-of-mean force and solubility enhancement coefficients, which describe the response of gas solubility to increasing micelle concentration. An analytical liquid drop model is proposed to describe the variation in argon solubility within micelles with increasing pressure.;Finally, we extend the study to examine the temperature effect and combined temperature and pressure effect on the gas solubilization for anionic and nonionic micelles. Enthalpy of micellization changing with temperature for nonionic surfactant is determined directly from molecular simulation. Constant values of critical micelle concentration on pressure vs. temperature plane are predicted based on the simulations covering a broad temperature and pressure range.
机译：表面活性剂胶束在一系列采油过程中可能面临极端温度和压力。从技术上讲，与压力有关的胶束组装会影响表面活性剂在诸如深海溢油的分散剂修复等应用中的表面活性剂功效，在深海溢油中压力从海底到水面变化很大。在非离子，离子和聚合物表面活性剂的临界胶束浓度中，疏水性物质转移热力学的压力依赖性反映为最大值，并且随着压力的增加，表面活性剂的体积符号从正向负随之变化。我们使用分子动力学模拟报告了离子和非离子表面活性剂对组装体积的压力影响。这些模拟证明，与压力折返组件相关的胶束体积符号的变化是由于组件中表面活性剂与单体相比的可压缩性提高而引起的，这在很大程度上可归因于胶束的烃核。基于水的近端分布，通过柯克伍德-布夫理论，分析了头基和尾基对胶束化量的贡献。接下来，我们研究了阴离子和非离子表面活性剂对压力对模型非极性气体氩的吸收的影响。胶束。胶束/溶质相互作用通过分子详细的平均势能和溶解度增强系数进行定量，描述了气体溶解度对胶束浓度增加的响应。提出了一种分析性的液滴模型来描述胶束内氩气溶解度随压力的变化。最后，我们扩展了研究范围，以研究温度效应以及温度和压力的联合作用对阴离子和非离子胶团的气体溶解作用。非离子表面活性剂的胶束化焓随温度的变化直接从分子模拟中确定。基于覆盖较宽温度和压力范围的模拟，可以预测压力与温度平面上的临界胶束浓度的恒定值。

著录项

  • 作者

    Meng, Bin.;

  • 作者单位

    Tulane University School of Science and Engineering.;

  • 授予单位 Tulane University School of Science and Engineering.;
  • 学科 Chemical engineering.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 116 p.
  • 总页数 116
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 物理化学（理论化学）、化学物理学;
  • 关键词

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