Adhesion of PDMS elastomers to functional substrates

The JKR technique was applied to study the influence of interfacial reactions on the adhesion between functional elastomer gels and functional solid substrates. The gelation chemistry of poly(dimethyl siloxane) (PDMS) gels cured by hydrosilylation reactions was purposely adjusted to produce an excess of either silane or vinyl functionality. Hemispherical lenses of these materials were then contacted under load with a variety of functionalized solid substrates: poly(styrene-b-butadiene) copolymers with vinyl functionality, vinyl-terminated trimethoxysilane self-assembled monolayers, and alpha,omega-functional PDMS brushes terminated with either monomethoxy or hydroxyl groups. To rule out chain interpenetration effects, the molecular weights were kept below the entanglement molecular weight or immiscible polymers were employed on opposite sides of the interface. Significant adhesion enhancement was observed for most systems, indicating that a variety of different interfacial reactions can occur across the interface between PDMS elastomers and solid polymeric substrates. The overall nature of the adhesion enhancement found is consistent with the predictions of the Lake-Thomas theory for failure of elastomers, increasing linearly with the length and areal density of covalent linker chains that span the interface.