# Effect of Charge Distribution Along Anionic Polyacrylamide Chains on Quartz Adsorption: A Molecular Dynamics Study

## TL;DR

This study uses molecular simulations to show how the arrangement of charges on polymer chains affects their adsorption on quartz surfaces.

## Contribution

The paper reveals that charge segregation in anionic polyacrylamides enhances adsorption stability on quartz surfaces.

## Key findings

- Polymers with extended neutral blocks show more stable adsorption on quartz than those with homogeneous charges.
- Charge segregation leads to compact conformations and reduced solvent accessibility.
- The results highlight charge-site distribution as a critical design parameter for polymer-surface interactions.

## Abstract

The interfacial behavior of polyelectrolytic flocculants is governed not only by their chemical composition but also by the molecular-scale distribution of charged and neutral segments, which directly influences transport, adsorption, and interfacial stability. In this work, classical molecular dynamics simulations are used to elucidate how charge-site architecture controls the conformation, dynamics, and adsorption stability of anionic polyacrylamides at the quartz–water interface. Polymer architectures ranging from homogeneous charge distributions to block-like arrangements were systematically analyzed at constant molecular weight and global charge density. The results show that increasing charge segregation induces more compact conformations, enhanced translational mobility in solution, and reduced solvent accessibility. At the interface, polymers containing extended neutral blocks exhibit significantly more stable adsorption on quartz than polymers with homogeneously distributed charges, consistent with the low surface charge density of silica. These findings demonstrate that charge-site distribution is an independent and critical design parameter governing polymer–surface interactions. From a chemical engineering perspective, the results provide fundamental insight relevant to the rational design of polymeric additives for solid–liquid separation, flocculation, and sustainable mineral processing applications.