Contact mechanics studies of polymer thin film adhesion

The work presented in this dissertation focuses on using the unique abilities of the JKR technique to probe the interfacial interactions of two independent polymer systems. To perform these studies, modifications were made to the JKR technique, including the integration of a thermal cycle to enable testing of thermally initiated interfacial interactions between two materials. Another enhancement of the JKR technique involved incorporation of cyclic testing to study crack growth under fatigue conditions.; These additions to the JKR technique were used in the analysis of interfacial interactions of poly(tetramethyl bisphenol-A polycarbonate) (TMPC) and poly(ethylene oxide) (PEO). Adhesion tests were performed on thin layers of PEO sandwiched between layers of TMPC, which were heated in contact above the melting temperature of the PEO and cooled back to room temperature before a cyclic fatigue test was performed. Additional characterization of the bulk and interfacial properties of this blend showed that these two polymers are miscible. From these studies, the interfacial interaction of the TMPC and PEO was found to be controlled by the PEO-mediated mixing of the TMPC layers.; In a second set of experiments, a model film consisting of a layer of acrylic diblock copolymer micelles was used to study the processes involved in the transfer of a viscoelastic film from a weakly adhesive elastomer substrate to a more strongly adhesive hemispherical glass indenter. Transfer of the film during tensile loading of the indenter began with expansion of a cavity at the film/elastomer interface, followed by subsequent delamination of the film at this interface. Criteria for cavity expansion and delamination are expressed in terms of the energy release rate. The critical energy release rate for cavity expansion increases linearly with the film thickness. A critical film thickness was identified above which films are able to peel from the elastomeric substrate over a region outside the original contact area with the indenter.