Adsorption in a nonsymmetric wedge.
We study adsorption in a nonsymmetric wedge consisting of two chemically different, homogeneous planes. First, we macroscopically analyze configurations of nonvolatile liquid drop placed in such a two-dimensional wedge and construct phase diagrams describing transitions between various interfacial shapes. Then adsorption is discussed within MFT based on the effective interfacial Hamiltonian. Two regimes for the system parameters--the wedge opening angle (2phi) and the critical wetting temperatures of each of the planar walls (T(W1) and T(W2), T(W2)<T(W1))--are identified. In one of them we find the critical filling transition at T(F)<T(W2) and the corresponding critical indices which are equal to those found for a symmetric wedge. In the other regime (T(W2)<T(F)<T(W1)) interfacial configurations are similar to those exhibited in the case of a planar substrate consisting of two chemically different parts. In the borderline case (T(F)=T(W2)), the interface profile above the wall with the lower wetting temperature becomes parallel to it. The line tensions corresponding to T(F)<T(W2) and T(F)=T(W2) cases are evaluated and the critical exponents - different in each case - are identified. An effective one-dimensional Hamiltonian describing fluctuations along the wedge is constructed for the T(F)<T(W2) case.
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Instytut Fizyki Teoretycznej, Uniwersytet Warszawski, Hoza 69, 00-681 Warsaw, Poland.
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