| An array of commercial products employ two or more polymers in a layered structure. In many cases, the applications for such products are limited by inferior mechanical properties resulting from a lack of polymer-to-polymer adhesion and interface strength. The goal of this research has been to understand the factors that affect the adhesion, including the properties of the component polymers, the benefit of adding molecules to enhance the adhesion, and the effect of processing on the mechanical integrity of the product. Explicitly, these included the fundamental parameters of interface width and entanglement density, which is the number of entanglements in the interfacial region, with a particular emphasis on the influence of the component polymers' properties. In polymer systems in which the adhesion is entanglement-based, it has been demonstrated that the adhesion can be directly correlated to calculable parameters. While large adhesion is often not required for commercial multilayered products, controlling adhesion is desirable. To have an interface with tunable adhesion required both the ability to enhance and decouple the interface. In addition to demonstrating methods of accomplishing this task, adhesion enhancement through the reaction of co-functional polymers has been shown to be dependent on the square of the initial concentration of functional groups. Lastly, orientational flow during multilayer coextrusion drastically reduced the adhesion in systems in which the adhesion was entanglement-based or reactively generated. Short annealing (30 seconds) in the melt restored the adhesion through chain relaxation and enhanced reaction rates. Exploration of these areas has increased understanding of adhesion, a scientifically significant interfacial phenomenon, and provided an opportunity to expand the applications base of polymer-polymer multilayered composites. |
