(573j) Direct Observation of Comb Polymer Dynamics in Semi-Dilute Solutions Using Single Molecule Imaging

Branched polymers play a key role in synthetic materials and plastics. Despite their increasing use in technological applications, we still lack a full understanding of the non-equilibrium flow behavior of topologically complex polymers. Owing to their complex chain architectures, comb-shaped polymers exhibit rich dynamic behavior that is not fully understood at the molecular level. In this work, we study the dynamics of single branched polymers in non-dilute solutions using single-molecule fluorescence microscopy (SMFM). We use a hybrid enzymatic-synthetic approach to synthesize DNA-based branched polymers (known as comb polymers) that contain a long backbone with multiple side branches grafted at various positions. The backbone and branches are dual-labeled with two different color fluorescent dyes to allow their simultaneous imaging and distinct tracking of backbones and branches separately. Following synthesis, we directly study the relaxation and transient stretching dynamics of single comb polymers in non-dilute solutions of linear unlabeled polymers in extensional flow. Interestingly, the dynamic behavior of comb polymers is markedly different in non-dilute polymer solutions compared to the dilute case. We directly observe 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. In all cases, we compare results for the non-dilute case to single comb dynamics in ultra-dilute solutions. Overall, our further extends the field of single polymer dynamics to topologically complex polymers, aiming to make a direct link between polymer microstructure and rheological properties.