New Frontiers in Single Polymer Dynamics

This talk will present the work of Professor Schroeder’s lab in extending the field of single polymer dynamics to new materials, including topologically complex molecules such as branched polymers and ring polymers. Single polymer studies offer the ability to directly visualize the dynamics of individual molecules in flow, which is a powerful method of characterizing microstructure. However, until recently, this technique has been mainly limited to linear double stranded DNA as a ‘model’ polymer system. Recently, Professor Schroeder’s lab has pushed the frontiers of single polymer dynamics to study non-linear chain architectures and block copolymers that spontaneously self-assemble into hierarchical structures.

Recent work on the synthesis of structurally defined polymers and single molecule studies of comb polymer dynamics will be discussed. Here, Professor Schroeder’s lab synthesized DNA-based comb polymers for single molecule imaging, and directly observed the dynamics of single branched polymers using fluorescence microscopy. Macromolecular DNA combs are synthesized using a hybrid enzymatic-synthetic approach, wherein chemically modified DNA branches and DNA backbones are generated in separate polymerase chain reactions, followed by a ‘graft-onto’ reaction via strain-promoted [3+2] azide-alkyne cycloaddition. Following synthesis, the lab studied the dynamics and properties of single comb polymers using single molecule fluorescence microscopy and microfluidics. This method allows for direct visualization of branched polymers, such that the backbone and side branches can be tracked independently using single- or dual-color fluorescence labeling.

Using this approach, the relaxation dynamics of single comb polymers from high stretch following the cessation of fluid flow can be studied. Results show that the molecular topology of individual branched polymers plays a direct role on the relaxation dynamics of polymers with complex architectures. Interestingly, polymer relaxation depends on branch grafting density and position of branch point along the main chain backbone. Overall, this work aims to extend single polymer dynamics to branched polymers and other non-linear topologies, which will allow for molecular-scale observation of polymer dynamics for complex systems.