Understanding molecular aspects of mass transport in charged and uncharged dense polymer networks

Polymer membranes are the future of separation, providing an energy efficient means of separation. Glassy polymer membranes have typically held the advantage over rubbery polymer membranes due to their higher selectivity; however, the work of this thesis aims to develop a molecular understanding of mass transport in dense rubbery polymer membranes to inspire the next generation of rubbery polymer membranes that can separate compounds based on size exclusion, combining the high permeability of rubbery polymer membranes with the high selectivity of glassy polymers. Imidazolium ionic liquid membranes were developed with varying ionic liquid moiety and crosslink density for the separation of toluene and heptane. TFSI- ionic liquid moieties showed improved toluene-heptane separation performance over their BF4- counterparts. Decreasing the crosslink density of the TFSI- polymerized ionic liquid membranes also led to a non-monotonic trend in permselectivity. The effect of crosslink density on mass transport was further investigated via probe diffusion in butyl acrylate polymer networks, where crosslinking significantly increased the glass transition temperature, reduced segmental dynamics, and reduced probe diffusion. Probe diffusion compared to segmental relaxation times revealed diffusion partially decoupled from segmental dynamics, where varying probe size led to a difference in diffusivity that could be accounted for by the inscribed probe volume. These results provide new insights regarding the effect of covalent crosslinks on probe diffusion necessary for the design and development of separation membranes.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science & Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Sheridan, Grant S.

Contributors dc:contributor

• Evans, Christopher M
• Schweizer, Kenneth S
• Braun, Paul V
• Sing, Charles E

• polymer
• polymer physics
• diffusion

Statement dc:rights

• Copyright 2022 Grant Sheridan

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/115466

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F115466