Shear-Induced Fracture at the Interface of PDMS and a Rigid Slab Modified with Polyelectrolyte Layers

We studied the interaction between a surface modified glass prism and a thin film of PDMS (polydimethylsiloxane) elastomer using a shear adhesion test. The glass prism was chemically modified either by depositing a self-assembled silane monolayer (silanization) or by depositing a few layers of polyelectrolytes. The PDMS was modified only with the polyelectrolyte layers (PEL). While the interaction between the chemically modified glass prism and unmodified PDMS (free of any filler additive) is primarily dispersive, some specific interaction prevails when the PEL-modified glass prism contacts a commercial PDMS (i.e., Sylgard (R) 184) that has silica additives. The surfaces were examined with wettability analysis, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) that established the locus of failure. Water immersion tests show that the adhesion between PDMS and glass is stable under water for a long time when the interfacial interaction is mainly dispersive, whereas it deteriorates rapidly when the interface has a polar character.