Extremely early onset of nonlinear viscoelasticity in dynamic shear of ideally monodisperse DNA

This work reports that the rheology of ideally monodisperse lambda (?) phage DNA solutions is extremely sensitive to the applied strain in dynamic oscilla-tory experiments. ? DNA exhibits nonlinearity at strains far smaller than what is observed in conventional synthetic polymers. However, it is found that poly-disperse calf thymus DNA does not exhibit the extreme strain sensitivity. By mixing samples of monodisperse ? DNA with the polydisperse calf thymus DNA, we correlate the molecular weight distribution (or polydispersity) to the onset of nonlinear viscoelasticity. We demonstrate that the strain sensitivity weakens as the polydispersity index increases. This is the first work correlating the inception of nonlinear viscoelasticity in entangled polymer system such as lambda DNA solution to the polydispersity of the samples. The experimental data suggests that ideally monodisperse polymer systems are very sensitive to the applied strain and have a very early transition to the nonlinear regime. We conclude that nominally monodisperse synthetic polymers are not sufficiently monodispersed to exhibit the early onset.

Automated summary

This work reveals that ideally monodisperse lambda phage DNA solutions show extreme sensitivity to applied strain in dynamic oscillatory experiments. Unlike conventional synthetic polymers, DNA exhibits nonlinearity at significantly smaller strains. Additionally, it is found that polydisperse calf thymus DNA does not exhibit the same level of strain sensitivity. By mixing samples of monodisperse DNA with polydisperse DNA, the researchers establish a correlation between molecular weight distribution and the onset of nonlinear viscoelasticity. The findings suggest that ideally monodisperse polymer systems are highly sensitive to strain and exhibit an early transition to the nonlinear regime.