Growth mode of a dichloromethane film physisorbed on MgO: thermodynamic characterization

Adsorption isotherms of dichloromethane (CH2Cl2) on MgO have been determine d between 175 and 200 K by means of volumetric measurements. The main conse quences of the electrostatic forces between CH2Cl2 molecular dipole moments and MgO surface electric held on the layer-by-layer condensation are a hig h value of the first layer isosteric heat of adsorption, competition betwee n two modes of condensation in the second layer range, and the formation of a third layer below 180 K, this wetting transition being governed by the g eometrical compatibility of the second and third layers. (C) 1999 Elsevier Science B.V. All rights reserved.