ADHESION PROMOTERS

Adhesion between a flat solid and a rubber is considerably increased b y grafting chains (chemically identical to the rubber) on the solid su rface. Similarly, a population of mobile chains dissolved into rubber can increase the strength of a rubber/rubber contact. A third (more re cent) type of promoter is a ''Guiselin brush'', obtained by incubating certain polymer melts against a suitable solid. A major practical pro blem is to understand how the adhesive energy varies with the surface concentration sigma of ''connector molecules'': very often, at high co nnector density, the strength goes down. We set up a theoretical pictu re of polymer interdigitation, covering most of the cases listed above . We also describe peeling measurements of the adhesion energy G(sigma ) for Guiselin brushes (silica/PDMS/PDMS network). For the Guiselin br ush, the statistical problem is much more complex. The main experiment al result is the presence of a clear maximum in the plot of G(sigma).