Accuracy of the blob model for single flexible polymers inside nanoslits that are a few monomer sizes wide

TL;DR

This study uses molecular dynamics simulations to evaluate the accuracy of the de Gennes' blob model for flexible polymers confined in nanoslits only a few monomers wide, revealing its surprising applicability beyond traditional limits.

Contribution

The paper demonstrates that the blob model accurately predicts static and dynamic properties of polymers in ultra-narrow nanoslits, extending its known range of validity.

Findings

Blob model explains static properties well even at few-monomer widths.

Dynamic spring constant remains consistent despite small blob size.

Results inform nanotechnology device design involving confined polymers.

Abstract

The de Gennes' blob model is extensively used in different problems of polymer physics. This model is theoretically applicable when the number of monomers inside each blob is large enough. For confined flexible polymers, this requires the confining geometry to be much larger than the monomer size. In this manuscript, the opposite limit of polymer in nano-slits with one to several monomers width is studied, using molecular dynamics simulations. Extension of the polymer inside nanoslits, confinement force on the plates, and the effective spring constant of the confined polymer are investigated. Despite of the theoretical limitations of the blob model, the simulation results are explained with the blob model very well. The agreement is observed for the static properties and the dynamic spring constant of the polymer. A theoretical description of the conditions under which the dynamic spring constant of the polymer is independent of the small number of monomers inside blobs is given. Our results on the limit of applicability of the blob model can be useful in the design of nanotechnology devices.