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Adhesion between two substrates is a complex phenomenon which at present is still not well understood. The important existing adhesion models (electrical, diffusion, thermodynamic adsorption, chemical, etc.) are reviewed in order to try to explain their mechanisms. Thermodynamic adsorption is now believed to be one of the most importnat mechanisms by which adhesion is achieved. Difusion and wetting are kinetic means in attaining good adsorption of a polymer at the interface. In the case of this model (thermodynamic adsorption), the notion of surface energy is developed and the importance of this property in the understanding of adhesion phenomena is emphasized. The methods of determining the surface characteristics of low and high energy solids are presented. The role played by acid‐base interactions in adhesion is also mentioned.

Freeze-fracture electron microscopy, quasi-elastic light scattering and 31P solid-state NMR have been utilized in order to follow morphological changes of melittin-dipalmitoylphosphatidylcholine complexes as a function of temperature. For lipid-to-protein molar ratios greater than 10 and up to 30, a reversible transition occurs, from discoidal structures of diameter N 100 to 400 A, at low temperature, to vesicular structures of diameter N 30~~~ A, at high temperature. This transition appears to be triggered by the phospholipid acyl chain melting. Higher concentrations of me&tin (e.g. lipid-to-protein ratio of 5.2) prevent this morphological transition, i.e. small complexes of N 100-250 A diameter remain stable throughout the temperature range. Melittin Phosphohpid membrane Disc-to-vesicle transition Chain melting Quasi-elastic fight scattering NMRFreeze-fracture

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The main surface treatments of materials (metals and plastics in particular) to be joined are presented. It is observed that these treatments modify the roughness, morphology, and chemical composition of the surface. As a result of these operations, the substrate surface energy is generally increased. A correlation is often noted between the increased surface energy and the assembly adhesive qualities.

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