Universal solvent quality crossover of the zero shear rate viscosity of semidilute DNA solutions

TL;DR

This study systematically maps the universal crossover behavior of zero shear rate viscosity in semidilute DNA solutions, revealing how solvent quality influences viscosity scaling with concentration and temperature.

Contribution

It introduces a universal crossover scaling function for DNA solution viscosity that accounts for solvent quality effects and provides experimental determination of key parameters like the theta temperature.

Findings

Viscosity follows a power law with concentration, modulated by solvent quality.

The theta temperature for DNA solutions is approximately 15°C.

Solvent quality parameter is determined via dynamic light scattering.

Abstract

The scaling behaviour of the zero shear rate viscosity of semidilute unentangled DNA solutions, in the double crossover regime driven by temperature and concentration, is mapped out by systematic experiments. The viscosity is shown to have a power law dependence on the scaled concentration $c/c^*$, with an effective exponent that depends on the solvent quality parameter $z$. The determination of the form of this universal crossover scaling function requires the estimation of the $\theta$ temperature of dilute DNA solutions in the presence of excess salt, and the determination of the solvent quality parameter at any given molecular weight and temperature. The $\theta$ temperature is determined to be $T_\theta \approx 15^\circ$ C using static light scattering, and the solvent quality parameter has been determined by dynamic light scattering.