Size Scaling of Neutral Polymers and Charged Polymers in Nanochannels

TL;DR

This study extends blob theory and uses molecular dynamics simulations to analyze how neutral and charged polymers behave in nanochannels across different confinement regimes, revealing distinct scaling laws and the effects of electrostatic interactions.

Contribution

The paper introduces an expanded blob theory for polymers in nanochannels and distinguishes new scaling regimes for charged polymers, including electro-de Gennes and modified transition regimes.

Findings

Identified five confinement regimes for neutral polymers with specific size scalings.

Discovered splitting of the de Gennes regime into Flory-de Gennes and electro-de Gennes for charged polymers.

Confirmed consistent chain size fluctuation scalings across neutral and charged systems.

Abstract

We expand the blob theory for freely-jointed chains and perform molecular dynamics simulations to study the behavior of polymers confined in cylindrical channels. From weak to strong confinement, five scaling regimes, de Gennes, extended de Gennes, transition, backfolding, and Odijk regimes, are distinguished for neutral polymers.The size scalings in each regime are derived as a function of the channel width. The scaling exponents $-1$ and $-1/3$ are obtained for the transition and backfolding regimes, respectively, which result from the reduction of the excluded volume of the segments by restriction of the segment's orientation in the narrowed channels. For charged flexible chains, the de Gennes regime is split into Flory-de Gennes and electro-de Gennes regimes owing to strong Coulomb repulsion in electrostatic blobs. Nonetheless, the extended de Gennes and transition regimes are shrunken. The study of the fluctuations of the chain size shows consistent scaling demarcations for both the neutral and charged chain systems.