复杂流体-固体界面相互作用热力学机制

具有复杂结构的纳微界面往往是界面复杂作用和宏观实验现象的主导因素。要准确描述界面处复杂流体的行为,需要引入能描述复杂流体-固体界面相互作用的分子热力学模型。本综述围绕分子热力学模型化方法拓展至纳微界面传递问题,提出"分子热力学建模+分子模拟+纳微实验"三者有机配合新思路。并针对复杂流体-固体界面相互作用的定量研究,着重综述了作者在热力学建模,分子模拟以及采用原子力显微镜(atomic force microscopy,AFM)实验方面的研究进展,创新性地提出将AFM定量化分析作为桥梁,用于构建分子模拟模型,描述复杂界面作用,揭示分子热力学机制,为构建纳微界面传递模型以及分子热力学模型由体相拓展至界面提供了可能。     

流体间界面热力学研究的进展

界面热力学是化学工程中一个重要的分支,它与流体相平衡、流体与流体间传质分离过程等密切相关。本文着重介绍界面分子热力学、两种流体相间界面张力的估算及表面张力在流体界面上吸附等热力学研究的状况,并预测了未来的发展前景。     

固体─超临界流体相平衡的分子热力学模型

从分子热力学基础出发提出一个适用于固体-超临界流体相平衡的理论模型，溶液中溶质的化学位分解为无限稀溶液化学位及溶质浓度效应两部.无限稀溶液化学位由简化的Oz方程计算，其中包括斥力贡献、局部组成及长程引力项浓度对化学位的贡献由作者根据Kirkwood-Buff溶液理论提出的修正Wilson模型计算．用45个二元系862个数据点对此模型进行检验并和PR方程（vdw-2混合规则）计算结果进行比较，本模型的平均绝对误差为11.7％，而PR方程的结果为14.9％，对极性溶剂体系的计算结果有显著改善.用此模型直接推算的萘-Co_2体系萘的偏摩尔焓和文献数据相吻合     

带电硬哑铃流体的分子热力学

Chemical potentials of charged hard-dumbbell fluids are obtained by Monte Carlo simulations using Widom‘s test-particle method, corresponding compressibility factors are achieved by integration of chemical potentials at different densities. A molecular thermodynamic model is also developed for these charged hard-dumbbell fluids where the residual Helmholtz function is composed of two terms: a reference term responsible for the charged hard spheres and a bonding contribution measuring the sticky interactions between positive and negative hard ions.Model predictions are in good agreement with simulation results.     

链状流体的分子热力学模型(Ⅰ)──纯物质

实际链状流体的分子热力学模型表示为参考流体（硬球链流体）的贡献与一微扰项之和.作者先前建立的硬球链流体的状态方程用于计算参考流体的性质,用Alder等人对方阱流体的计算机模拟结果计算微扰项的贡献,从而建立了实际链状纯流体的分子热力学模型.该模型具有非常简单的形式,用三个与温度无关的分子参数（分子的链数,链节的直径和链节间的方阱位能阱深）可以较好地关联从球形小分子到链状高分子、分子间没有氢键作用的流体的饱和蒸汽压、饱和液体体积和pVT关系     

利用二维流体分子热力学模型计算气体混合物在固体界面的吸附等温线

结合流体混合规则,将之前建立的二维变阱宽方阱链流体分子热力学模型（SWCF-VR-2D）扩展至混合流体,并利用模型计算了甲烷/二氧化碳、甲烷/氮气和甲烷/乙烷等气体混合物在不同吸附剂上的吸附等温线。由于混合气体间的相互作用会使得混合气体的吸附不同于单一气体的吸附,通过调节气体与固体壁面间的相互作用参数ε_w以描述这种变化。调节能量参数后模型能满意计算混合气体的吸附等温线,总的平均偏差为5.06%。     

受限界面处流体分子行为的调控及相关分子热力学模型初探：基于高比表面氧化钛的研究进展

纳米受限界面处的流体由于受到界面性质的影响显著,且存在复杂的传递和反应机制耦合问题,其流体分子行为难以调控,成为了现代化工新技术（如膜过程、多相催化）突破的瓶颈。结合了近几年本课题组的相关工作进展,以化学性质稳定的高比表面氧化钛作为研究平台,对界面处流体分子受限行为进行分析,研究了传递和反应机制分别对界面处流体行为的影响,并探索其调控机制;同时对建立的相应分子热力学模型进行了初步探索,通过原子力显微镜技术将界面摩擦性质和分子间相互作用关联,为分子热力学模型提供分子参数。     

复合材料界面相互作用的分子模拟研究与进展

综述了MD(分子动力学)模拟技术、计算复合材料界面粘接力的MD模型构建与模拟方法,概括了MD在研究复合材料界面相互作用中的研究现状;最后对MD的发展方向进行了展望。     

氩流体汽液界面特性的平衡分子动力学模拟

采用L—J模型,对氩流体汽液界面特性进行了平衡分子动力学模拟,得到了密度、界面张力等参数的分布规律。模拟结果表明,随着氩流体体系温度的提高,液相主体密度和界面张力逐渐减小,汽相主体密度和界面厚度逐渐增大;随着截断半径的增大,界面张力逐渐增大,汽相主体密度及界面厚度稍有减小,液相主体密度稍有增大;随着模拟分子数的增加,界...     

链状流体的分子热力学模型(IV)高分子系统的液液平衡计算

将作者先前提出的链状流体混合物的分子热力学模型应用于高分子系统液液平衡的计算,对具有最高会溶温度（UCST)和最低会溶温度（LCST）的高分子共混物的液液平衡,采用两个相互作用参数可以取得令人满意的关联结果。对具有LCST的高分子溶液的液液平衡计算,需对高分子链长作适当调整。     

材料化学工程科学内涵及方法初探:从介观尺度界面流体行为出发认知材料

作为一门新兴的交叉学科,材料化学工程科学内涵的进一步凝练和方法论的建立显得十分重要和迫切。介观尺度下界面流体的研究对于材料化学工程具有重要意义,材料化学工程的科学内涵在于通过认识介观尺度下界面处流体行为来"认知"材料,以期建立材料结构、性能(应用)与制备(生产)三者之间的关系。其中,弄清介观尺度下复杂作用和复杂结构对界面流体行为的影响,是"认知"材料的关键。分子模拟技术作为单因素遴选介观尺度各影响因素的有效手段,在实际应用中存在两大难点:如何同时获得界面流体反应和传递两个方面的信息;如何实现分子层面认识在材料应用层面的转化。基于此,初步讨论了材料化学工程研究方法的发展趋势。     

A simple kinetic model for complex rheological fluids based on irreversible thermodynamics

In this work, we analyze the kinetics of the entanglement–disentanglement process of complex fluids coupled to a rheological constitutive equation of state within an irreversible thermodynamics framework. In the context of the coupling between the kinetics and the mechanical phenomena, we assume that the rate constants are functions of the affinities that contain the chemical potentials, which are themselves functions of the extended Gibbs free energy containing the irreversible dissipation terms. Although the derived model has a simple mathematical structure, it is able to predict complex flow behaviors, including shear-thickening, shear-thinning, and more complex flow histories such as shear-banding. As special case, we derive the constitutive equations of the Bautista–Manero–Puig (BMP) model in which the material constants have a thermodynamic basis and have been successfully used for the last two decades to predict the behavior of complex fluids such as the ones examined here.     

Calculations of complex phase equilibrium by equal‐area method

The equal‐area (EA) method is studied with respect to its applicability to a wide range of phase equilibrium scenarios for pure fluids and binary mixtures. The study covers vapor‐liquid equilibrium (VLE), liquid–liquid equilibrium (LLE), solid‐liquid equilibrium (SLE) and their crossover transitions. The thermodynamic models studied include equation of state, activity coefficient and solid solubility models and their combinations. The performance of the EA method for chain molecules, at very low temperature and nearby the critical point is also investigated. We conclude that the EA method is very reliable and efficient and has a number of advantages over the conventional method. Finally, we apply the EA method to the regression of the model parameters to demonstrate its attractive application. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Thermodynamic approach to interfacial transport phenomena: Single‐component systems

Balancing extensive quantities at interfaces in terms of excess densities is a subtle problem because these densities change with the precise location of the dividing surface within the interfacial region. We propose to handle such ambiguities for moving interfaces by introducing a gauge degree of freedom associated with the location of the dividing surface and by studying all the normal velocities associated with different excess densities. Unambiguous interfacial balance equations can then be obtained directly from the differences between normal velocities. By assuming local equilibrium, considering the interfacial entropy balance, and identifying the entropy production rate at the interface, we are naturally led to thermodynamically consistent constitutive assumptions for the fluxes characterizing transport in the interface and for the boundary conditions characterizing transport across the interface. The usefulness and generality of the proposed approach is illustrated in the context of several examples. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1424–1433, 2014     

Predicting NRTL binary interaction parameters from molecular simulations

A predictive approach for calculating the binary interaction parameters ( ) of the nonrandom two liquid (NRTL) local composition model is developed, combining molecular simulations with the two‐fluid theory. The binary interaction parameters are determined for the following three sets of model binary mixtures: water + methanol, methanol + methyl acrylate, and water + methyl acrylate. For each binary mixture, the interaction parameters are expressed in terms of molecular size and strength of interactions, which are in turn, calculated from molecular simulations. We show that the binary interaction parameters determined from simulations are in qualitative agreement with those estimated from regressing experimental data. The major factors that determine the binary interaction parameters are outlined based on simple thermodynamic arguments for each mixture. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2758–2769, 2018     

CO2浓度对混溶态(CO2+正己烷)/盐水界面微观特性的影响

在CO₂以超临界状态封存于油气藏时,储层中流体间的界面性质是影响封存效率和封存量的重要因素。利用分子动力学模拟的方法,对330 K、20 MPa混溶条件下(CO₂+正己烷)/NaCl溶液系统的界面微观性质进行了研究,分析了混溶相中CO₂摩尔分数变化时,界面处CO₂和正己烷的亲水、疏水特性及其影响,为CO₂地质封存提供理论依据。研究发现,随着混溶相中CO₂摩尔分数的增加,界面厚度及粗糙度增大,分子渗透加深,热波动加剧。界面上CO₂与水之间更强的相互作用造成了CO₂注入过程中界面张力的降低。CO₂表现出类似于表面活性剂的性质,并在CO₂摩尔分数为65%(质量分数为50%)时,其界面累积量以及正己烷的驱离量最大。界面处存在特殊的分子微观结构,CO₂、水及正己烷分子呈现特殊的排布方式。     

蛋白质分子与固体表面相互作用的分子模拟

蛋白质分子和固体表面的相互作用在与生物有关的材料以及工程领域有着重要的影响.两者相互作用的复杂性使得单纯依靠实验无法得到完整的信息.利用分子模拟，从分子尺度上对蛋白质和固体表面的相互作用进行研究，有助于更清楚地了解决定蛋白质在固体表面行为的原因.本文综述了蛋白质与固体表面相互作用的分子模拟研究，主要介绍有关蛋白质模型的选择、表面对蛋白质吸附能力的机理以及蛋白质在吸附表面的取向和构型变化的研究现状和成果.     

The effect of polymer surface modification via interfacial polymerization on polymer–protein interaction

Membrane separation is an important processing technology used for separating food ingredients and fractionating value‐added components from food processing byproducts. Long‐term performance of polymeric membranes in food protein processing is impeded by the formation of fouled layers on the membrane surface as a result of protein adsorption onto the membrane surface. Surface modification of synthetic membranes, i.e., changing surface characteristics to reduce protein adsorption permanently, is one of the innovative ways of reducing the fouling of membrane surfaces. In this study, surface modification of flat‐sheet ultrafiltration membrane, polyethersulfone (PES), was investigated in improving the hydrophilicity of PES surfaces, thereby reducing adsorption of the protein caused by hydrophobic–hydrophobic interaction between the protein and the membrane. Hydrophilic polymer grafting through thin‐film composite using interfacial polymerization was employed to improve the hydrophilicity of the commercial PES membranes. Poly(vinyl alcohol), poly(ethylene glycol), and chitosan were chosen as hydrophilic polymers to graft on PES membrane because of their excellent hydrophilic property. Modified PES membranes were characterized by contact angle, FTIR, XPS, and AFM. Contact angles of modified PES membranes were reduced by 25 to 40% of that of the virgin PES membrane. XPS spectrum supported that the PES membranes were successfully modified by interfacial polymerization. Tapping‐mode AFM was used to examine the changes in surface topography of modified PES membranes. The PES membranes modified by interfacial polymerization showed lower roughness (from 1.2 to 2.0 nm) than that of virgin PES membrane (2.1 nm). The results of these instrumental analyses indicated that the PES membranes were successfully enhanced hydrophilically through interfacial polymerization. The protein adsorption on the modified membranes was reduced by 30 to 35% as a result of surface modification of the PES membranes using interfacial polymerization technique. Published 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

高分子溶液的分子热力学进展

综述了近年来高分子溶液分子热力学领域的一些进展,认为与密度有关的模型,如状态方程,是该领域发展总的趋势,同时,迫切需要更精确、全面的实验数据。在该领域的研究中,分子模拟将发挥重要作用。