(402a) In-Situ Monitoring of Block Copolymer Ordering In Solution-Cast Films During Solvent Removal

The manner in which solvent is removed during the solution-casting of block copolymer films has a significant influence on the polymer morphology in the final film, which in turn governs film properties. These solution-cast films have various applications, including the processing of polymer electrolyte membranes for fuel cells and reverse osmosis water purification membranes. It is, therefore, desirable to understand the mechanism by which ordered structures develop during the drying process.  We have developed a new small angle X-ray scattering method that allows for real-time tracking of the phase separation of block copolymers as solvent is continually extracted from a film. These experiments are capable of tracking changes in the ordering kinetics and domain dimensions as a function of concentration across the order-disorder transition and deeper into the phase diagram.  The effect of drying temperature on the ordering kinetics and domain compression is explored.  Removing solvent in the presence or absence of a sweep gas allows the effect of drying rate on the ordering process to be decoupled from the effect of drying temperature. In addition, iso-concentration measurements of the ordering kinetics at various concentrations along the drying path can be made using SAXS and compared to the phase kinetics measured using rheology. Trends in the ordering kinetics observed in these iso-concentration phase separation experiments will be compared to those observed in in-situ ordering experiments.