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Polymer thin films play an increasingly important role in technological applications ranging from coatings, adhesives and lithography to organic light emitting diodes and various organic material based devices, including sensors.
The physical properties of materials, small molecule, atomic or long chain polymers, confined to sufficiently small dimensions by external “walls” are generally difficult to predict because they manifest the influence of a confinement as well as the influence of interfacial interactions between the material (chemical) constituents and the external “walls.” To this end, polymer films below a certain thickness range often exhibit physical properties that differ substantially from intrinsic bulk behavior. This is due, in part, to the increasing influence of entropic effects (confinement and chain “packing”) and interfacial interactions as the film thickness decreases. Properties such as the glass transition temperature, phase separation temperatures, viscosity and translational chain diffusion exhibit apparent film thickness dependent behavior. Moreover, the wetting properties of films in the thickness range of nanometers, or tens of nanometers, are influenced by long-range intermolecular interactions, unlike thicker films in the micron thickness range (see figure).
The goal of our research is the development of a fundamental understanding of the influence of confinement and interfacial interactions on the properties of thin polymer films. Three areas are emphasized:
1) The Glass Transition of thin polymer films
2) Effect of interfacial forces on the structure of thin films
3) Block Copolymer Thin Films
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