| Summary: | The fundamental study of Lewis acid/base interactions presented in this dissertation demonstrates the role of these interactions in adhesive phenomena. The model systems investigated were representative of real substrates and soft, viscoelastic adhesives where, in one case, favorable acid/base interactions were possible which were not possible in the other. Inverse gas chromatography (IGC) and Infrared spectroscopy (IR) techniques were used to analyze the model adhesive in terms of its acid/base nature. The results of both experiments indicated, through negative enthalpies of acid/base interaction with acidic solvents, that the model adhesive poly(2-ethyl hexyl methacrylate) (PEHMA) exhibits the properties of a Lewis base. The near quantitative agreement of the results from both experiments validate these methods of determining acid/base interactions in polymeric systems. Fitting the enthalpies for acid/base interaction to Drago’s and Gutmann’s models brought out the importance of the electrostatic component of the interactions investigated. Furthermore, they illustrated the need to expand the existing datasets beyond organo-meta1lic compounds, and include more common organic solvents.
Results from X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) analysis of the model substrate, grade 2 titanium, pretreated via chromic acid (CAA) or sodium hydroxide anodization (PSHA), confirmed that oxides of very similar topology can be produced. Indicator dye studies revealed the CAA-Ti had a surface pH of below 3.0 and the PSHA-Ti had a surface pH of above 8.0.
Bonds constructed from these analyzed materials were tested in peel and both systems exhibited good adhesion. However, the bonds in which favorable interactions were possible demonstrated superior interfacial performance. This improvement was seen in the bond’s ability to resist adhesive (interfacial) failure at debond rates at which other bonds failed. When the test geometry was changed such that the stress intensity at the interface was increased, the bonds in which acid/base interactions were favorable supported a higher peel load. === Ph. D.
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