Visualizing and controlling polymer nanostructures through in situ optical imaging and synthesis

Over the past decade, super-resolution optical microscopy has been an enabling advance in nanoscale characterization, initially for biological problems but now increasingly in the polymer community. Our group is exploring these techniques in a variety of systems including polymer blends, brush polymers, polyelectrolytes, elastomers, and block copolymers. In this talk, we will present several of these studies. As an example, we have been able to measure the persistence length of bottlebrush polymers in the melt for the first time, through fluorescent labeling of single isolated chains mixed with an unlabeled matrix. We have also detected mechanical deformation at the nanoscale by examining local distributions of fluorophore orientation, visualizing regions as small as 15 nm. Finally, we demonstrate time-lapse imaging in solvent-swollen polymer blends, where coarsening behavior and self-assembly is readily observed.

In addition to characterization, it is important to control polymer nanostructures, which are often governed by the underlying polymer chemistry particularly in self-assembly approaches. Polymer chemistry and physics are often treated separately, where polymers are first synthesized and then self-assembled into their desired morphologies in a second step. Here, we demonstrate a process for photopolymerization within a self-assembled block copolymer film. This process enables real-time control over both domain spacing and morphology on demand. The regions of photopolymerization can be modulated by photomasks for obtaining distinct structures on a single substrate. We use this process in the application of patterned photonic crystals.