MODEL EXPERIMENTS ON ELASTOMER-SOLID ADHESION

The adhesion energy between polydimethylsiloxane (PDMS) elastomers and flat silica surfaces modified by irreversible adsorption and end graf ting of PDMS chains, has been characterised through peel tests and J.K .R. experiments. The PDMS layer is a Guiselin ''pseudo-brush'', made o f highly polydisperse loops. Irs structure can be adjusted by varying the polymer volume fraction Phi in the grafting reaction bath. In the limit of very low velocity for the propagation of the fracture, both t he peel and the J.K.R. tests exhibit adhesion energies going through a maximum for Phi close to 30%. This result can be interpreted in terms of a limitation of the interdigitation between the chains of the pseu do-brush and the elastomer at high surface chain density, due to the a ssociated swelling of the elastomer.