Direct observation of DNA dynamics in semi-dilute solutions in extensional flow

Abstract

The dynamic behavior of semi-dilute polymer solutions is governed by an interplay between solvent quality, concentration, molecular weight, and flow type. Semi-dilute solutions are characterized by large fluctuations in concentration, wherein polymer coils interpenetrate but may not be topologically entangled at equilibrium. In non-equilibrium flows, it is generally thought that polymer chains can self-entangle in semi-dilute solutions, thereby leading to entanglements in solutions that are nominally unentangled at equilibrium. Despite recent progress, we still lack a complete molecular-level understanding of these dynamics. In this work, we use single molecule techniques to study the dynamics of semi-dilute solutions of DNA in planar extensional flow, including polymer relaxation from high stretch, transient stretching dynamics in step-strain experiments, and steady-state stretching in flow. Our results are consistent with a power-law scaling of the longest polymer relaxation time in semi-dilute solutions, revealing an effective excluded volume exponent $\nu$ = 0.56. We further studied the non-equilibrium stretching dynamics in extensional flow, with results showing a decrease in transient polymer stretch at moderate Weissenberg number and a milder coil-to-stretch transition in semi-dilute solutions compared to dilute solutions. Interestingly, a unique set of molecular conformations during the transient stretching process for single polymers in semi-dilute solutions is observed, which suggests transient stretching pathways for polymer chains in semi-dilute solutions are qualitatively different than dilute solutions due to intermolecular interactions. Taken together, this work provides a molecular framework for understanding the non-equilibrium stretching dynamics of semi-dilute solutions in strong flows.

arXiv comment40 pages, 11 figures

References in corpus (8)

• Semidilute Polymer Solutions at Equilibrium and under Shear Flow
• Self-diffusion and Cooperative Diffusion in Semidilute Polymer Solutions as measured by Fluorescence Correlation Spectroscopy
• Optimisation of a Brownian dynamics algorithm for semidilute polymer solutions
• Universal solvent quality crossover of the zero shear rate viscosity of semidilute DNA solutions
• Parameter-free prediction of DNA dynamics in planar extensional flow of semidilute solutions
• Dynamic crossover scaling in polymer solutions
• The viscosity radius in dilute polymer solutions: Universal behaviour from DNA rheology and Brownian dynamics simulations
• Enhancement of coil--stretch hysteresis by self-concentration in extensional flows, and its implications for capillary thinning of liquid bridges of dilute polymer solutions

Cited by in corpus (13)

• Single Polymer Dynamics for Molecular Rheology
• Pore-Scale Flow Characterization of Polymer Solutions in Microfluidic Porous Media
• Dynamically Heterogeneous Relaxation of Entangled Polymer Chains
• Universal dynamics of dilute and semidilute solutions of flexible linear polymers
• Unexpected entanglement dynamics in semidilute blends of supercoiled and ring DNA
• Parameter-free prediction of DNA dynamics in planar extensional flow of semidilute solutions
• Shear thinning in dilute and semidilute solutions of polystyrene and DNA
• Dynamics and Rheology of Ring-Linear Blend Semidilute Solutions in Extensional Flow: Single Molecule Experiments
• A study of the morphology, dynamics, and folding pathways of ring polymers with supramolecular topological constraints using molecular simulation and nonlinear manifold learning
• Dynamics and Rheology of Ring-Linear Blend Semidilute Solutions in Extensional Flow: Modeling and Molecular Simulations
• Simulation of semidilute polymer solutions in planar extensional via conformationally averaged Brownian noise
• Uniaxial extensional viscosity of semidilute DNA solutions
• Tumbling dynamics of inertial chains in extensional flow