Molecular Confinement on Nanostructured Polymer Surfaces

Polymers have characteristic dimensions of assembly which depend on processing, especially in nanofabrication. These dimensions may be important in properties such as electrical or thermal conductivity. These properties will be strongly affected when fabricated polymer nanostructures have dimensions comparable to the critical length scale of physical phenomena (mean free path of electrons, mass transport, etc.). Enhanced mechanical, optical, and electrical properties of nanostructures, including nanopillar arrays less than 1 µm tall, have been well documented. We fabricated nanostructures on poly(methyl methacrylate) surfaces with nanoimprint lithography. A consequence of such a process is confinement induced reordering of polymer chains which is affected by the mold geometry, surface properties, and imprinting variables. Using thermal imprinting, and the combined topographical and nanoscale chemical mapping of photoinduced force microscopy, we found that nanopillars (100-700 nm range) confine functional groups differently depending on the feature shape, height, and periodicity. These findings suggest that surface chemistry, as well as nanoscale phenomena, can be controlled for use in adhesion and bio-electronic interfaces.