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The surface and interfacial energies of polymers are measured using the JKR‐type experiments. A novel method has been developed to prepare samples of glassy polymers for adhesion measurements. A thin layer of a polymer is coated on the surface of an O2‐plasma modified cross‐linked poly(dimethylsiloxane) [PDMS] spherical cap resulting in the formation of a composite. Using the JKR theory, the surface energies of polystyrene [PS] and poly(methyl methacrylate) [PMMA] are determined from the measurements of the contact radius as a function of applied load. The results of the JKR‐type experiments are compared to adhesion measurements done using the surface forces apparatus (SFA). Adhesion hysteresis was observed for PS‐PS contact as well as PMMA‐PMMA contact. However, no hysteresis was observed for PDMS‐PDMS, PDMS‐PS, and PDMS‐PMMA contacts. The exact origin of the hysteresis is not clear at present. The current evidence suggests that hysteresis is due to rearrangement of the interface during contact.

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The contact mechanics-based Johnson−Kendall−Roberts technique has been used to study the adhesion of cross-linked 2-ethylhexyl acrylate-co-acrylic acid (2EHA-co-AA) elastomers as models of pressure sensitive adhesives (m-PSA). We have addressed the effect of m-PSA composition on intrinsic solid surface energetics and on the mechanical performance of m-PSA. The measured surface energies of the m-PSA were all approximately 30 mJ m-2, indicating surfaces dominated by methylene groups. The extent of adhesion hysteresis for the m-PSA used in our measurements was not a strong function of acrylic acid content implying that the main mechanism contributing to the adhesion of practical un-cross-linked or lightly cross-linked PSA is the viscoelastic dissipation. Several technical and physical issues concerning contact mechanical measurement of adhesion and the observed rate-dependent patterns of adhesion have been addressed.

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