(503g) Single Molecule Studies of Comb Polymer Dynamics in Semi-Dilute Solutions

Branched polymers play a key role in modern technology such as chemical sensing, lab-on-chip devices, and optically active materials. Despite their increasing importance, our current understanding of the non-equilibrium dynamic behavior of these topologically complex polymers is limited and is largely based on bulk rheological and experimental scattering data. Owing to their complex molecular architectures, comb-shaped polymers exhibit rich dynamic behavior that is not fully understood at the molecular level. To address this problem, we study the dynamics of single branched polymers in non-dilute solutions using single-molecule fluorescence microscopy (SMFM). In particular, we use a hybrid enzymatic-synthetic approach to synthesize DNA-based branched polymers (comb polymers) that contain a long backbone with multiple side branches grafted at various positions. Following synthesis, we directly study the transient stretching dynamics of single comb polymers in semi-dilute solutions in extensional flow. We compare the transient stretching dynamics of single comb polymers in semi-dilute solutions of linear unlabeled polymers to the dynamics of comb polymers in ultra-dilute solutions. Interestingly, the transient stretching dynamics and relaxation behavior of comb polymers is markedly different in non-dilute polymer solutions, which reveals changes in molecular-scale dynamics due to chain branching and chain-chain intermolecular interactions. We further study the effects of background concentration and polymer topology on comb polymer dynamics in order to elucidate the non-equilibrium behavior of topologically complex polymers. Overall, our work shows that single polymer dynamics can be used to provide a direct link between polymer microstructure and bulk rheological properties.