Analysis of molecular morphology and permeation behavior of polyimide-siloxane molecular composites for their possible coatings application

This study investigates two different molecular composite coatings (MCCs). All the components as well as compositions constituting each MCC were synthesized and characterized employing different analytical techniques. Studies of the surface morphology of the MCCs have shown heterogeneous distribution and phase separation in coatings. Theoretically calculated Gibbs free energy of mixing showed that phase separation in MCCs occurred with the increase in concentration of the minor component in major one. Different types of domain morphologies have been revealed and the probable mechanism of their formation has been detailed. An understanding of the absorption and hence percolation of water molecule through the succeeding layers of MCCs has been developed. Various factors governing the diffusional phenomenon has been studied and correlated with the underlying phase separated microstructures of MCCs. (c) 2006 Elsevier B.V. All rights reserved.