Manipulation of Polymer/Polymer Interface Width from Nonequilibrium Deposition

We demonstrate, using neutron reflectivity, that the width of a nonequilibrium interface between an organo-soluble aromatic polyimide film and triacetate cellulose (TAC) support film created by spin-coating or solution-casting can be broadened in a controllable way using a “swelling agent” in the deposition process. In a favorable case, the adhesion, as measured by T-peel tests, can be increased by a factor of 7 by adjustment of the solvent composition. The morphologies of the TAC fractured surfaces after peeling tests measured by AFM reveal that broadening of the interfacial width causes an interconnected network in the interface, leading to a sharp increase in the interfacial adhesion. Differences in the chemistry (solubility) of the materials being deposited do make a difference in the effectiveness of this strategy of using a “swelling agent”. For one polyimide, a 3-fold increase in adhesion can be obtained by optimizing the deposition temperature, but this approach for improving adhesion is less effective than that of adding “swelling agent”. The formation of robust interfaces of this type is important because of the critical roles that multilayer films containing polymers with special properties and tailored structures play in applications as diverse as computer displays, photovoltaic devices, and polymeric electronics. The “swelling agent” strategy makes it possible to produce polymer multilayer structures in a cost-effective way with roll-to-roll mass production using direct solution coating