Simulation of Weak Polyelectrolyte Brushes

Using molecular simulations, the stimuli-responsive behavior of weak polyelectrolyte brushes (PEBs) and weak polyampholyte brushes (PABs) was examined with respect to pH, salt concentration, monomer sequence and grafting density. While PEBs have only acidic or basic monomers, PABs contain both types of monomers, resulting in more complex interactions that require advanced simulation methods to properly investigate. As expected, the simulation results of PEBs are qualitatively consistent with previous experimental and theoretical studies, showing a crossover from the "osmotic" brush regime into the "salted" brush regime as salt concentration is increased. In contrast, the ionization state, brush height, lateral structure, and chain conformations of PABs vary with pH and salt concentration in ways that are qualitatively different from PEBs. While grafting density has a moderate impact on the response of PABs, monomer sequence and salt concentration play significant but different roles depending on pH conditions. At extreme pH conditions, salt concentration has a more prominent effect on PABs, because only one type of monomer is charged, and electrostatic repulsion is the dominant factor. Within the neutral pH range, monomer sequence becomes more important in regulating brush behavior due to electrostatic attractions prevailing when all acidic and basic monomers are charged. The findings in this work indicate that monomer sequence and salt can be leveraged to adjust the pH response of weak PABs to achieve the desired outcome when designing stimuli-responsive materials.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Chemical Engineering

Grantor

University of Houston

Year dc:date.issued

2025

Author dc:creator

• Yuan, Xin

Advisor dc:contributor.advisor

• Palmer, Jeremy C

Committee members dc:contributor.committeemember

• Zerze, Gül H
• Conrad, Jacinta C
• Hatch, Harold W
• Marciel, Amanda B

• Chemical engineering

Language dc:language.iso

English

Handle dc:identifier.uri

https://hdl.handle.net/10657/19516

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/19516