Towards Understanding CO2 Assisted Nano-Scale Processing of Polymer Thin Films

Supercritical CO2 has been established as a very promising polymer processing solvent for many macro-scale applications such as manufacture of polymer foams. However, extension of this processing technique to nanometer length scales, in particular to applications involving polymer thin films, requires a fundamental understanding of such systems at the molecular level. In this talk, we will present results for patterning of polystyrene thin films using a nano-processing technique known as CO2 assisted Nano-Imprint Lithography (CO2-NIL).

As shown in previous talks, polymer density functional theory (PDFT) is an extremely effective tool for studying the fundamental properties of CO2 pressurized polymer thin films. This theory offers semi-quantitative information at lower computational costs as compared to computer simulation. The basic idea of PDFT is to express the free energy as a functional of spatially varying density distribution, from which equilibrium density distribution and other thermodynamic information can be derived. Using PDFT, we will show how CO2 affects polystyrene films at nano-length scales and thus facilitates Nano-Imprint Lithography.