On the incompatibilities of interaction scales and processes with focus on the work of adhesion

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    Abstract

    The mutual compatibility of Hamaker constants, solubility parameters or cohesive energy densities (CED) and surface/interface tensions are evaluated. It is shown that the partial contributions (dispersive, Lifshitz–van der Waals, dipolar induction, dipolar orientation, polar, acid, base and hydrogen bond) to Hamaker constants, solubility parameters or cohesive energy densities and surface/interface tensions are mutually inconsistent. The published reference data for a single set of liquids is moreover shown to be exceedingly scattered; making the parallel use of these scales challenging. Reference processes designed for bringing two and three phases into mutual contact are conflicting. The two-phase processes within Hamaker and exchange energy density (EED) frameworks agree, but the three-phase models differ. As a free-standing parameter the EED is however comparable. The two-phase adhesion process is shown to be incompatible with the other contact processes and the three-phase adhesion process is opposite to them. One reason for this controversy is the different averaging of interfacial properties. While interfacial Hamaker constants and solubility parameters or cohesive energy densities are geometric averages of corresponding intervening phase properties, this practice is replaced by the work of adhesion being geometrically averaged as works of cohesion. As a result, there exist three conflicting models for the adhesion process: the Dupré work of adhesion, the Girifalco–Good geometric averaged works of cohesion and Fowkes reduced interfacial or interphasial tension process. None of these agree with the commonly accepted standard Hamaker contact processes and they should be replaced with the compatible extended work of adhesion process originally suggested by Dupré. The models offered for the conversion of Hamaker constants and solubility parameters or cohesive energy densities to surface tensions involve conversion factors and equilibrium distances between planes of molecules in liquids. The equilibrium distance for different close packings derived from molar liquid volumes are about 2–5 times larger than the cutoff distances obtained from simulations. Using volumetric equilibrium distances, the conversion factors for dispersive, polar and total Hamaker constant and solubility parameter or cohesive energy densities to surface tensions become nearly equal but they are different for each liquid.
    Original languageUndefined/Unknown
    Pages (from-to)89–107
    JournalAdvances in Colloid and Interface Science
    Volume234
    DOIs
    Publication statusPublished - 2016
    MoE publication typeA1 Journal article-refereed

    Keywords

    • ACID-BASE BALANCE
    • adhesion
    • colloidal interactions

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