Solvent effect on the roughening transition and wetting of n-paraffin crystals

Abstract The solubility parameters, roughening temperatures and edge free energies have been measured as a function of temperature and interpreted for n-C 23 H 48 and n-C 25 H 52 crystals. The crystals have been grown from solutions consisting of n-hexane and toluene mixtures. The dissolution enthalpy is used to determine the strongest bond in the bulk of the crystal Φ str bulk and the roughening temperature is used to determine the strongest bond in the crystalline interface Φ str int . The ratio of these two bonds is called the wetting κ of the crystalline interface. It turns out that the solutions containing mixtures of n-hexane and toluene behave according to a regular solution, which follows directly from thermodynamics with the use of a mean field approach. The strongest bond in the bulk of the crystal has the same dependence on the composition of the solution as the dissolution enthalpy. In contrast with this, the strongest bond in the interface stays approximately constant and, therefore, the dependence of the wetting κ on the composition of the solution follows that of the enthalpy of dissolution.