Amphiphilic Block Copolymer and Ionic Liquid Composite Materials for Biphasic Gas Separation Membranes

Author

Charlie Brandon Knight, University of MississippiFollow

Date of Award

1-1-2025

Document Type

Thesis

Degree Name

M.S. in Engineering Science

First Advisor

Adam E. Smith

Second Advisor

Alexander M. Lopez

Third Advisor

Sasan Nouranian

School

University of Mississippi

Relational Format

dissertation/thesis

Abstract

Amphiphilic block copolymers (BCPs) act as polymeric surfactants in solution, enabling self-assembly into micelles with defined mesoscale morphology. The self-assembly of micelles enables solubilization or encapsulation of otherwise insoluble compounds. Notably, one application for amphiphilic BCPs is the encapsulation of room temperature ionic liquids (RTILs) for synthetic membrane casting solutions. Imidazolium-based RTILs, like 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) are known for their high CO2 affinity and low vapor pressure. Due to the high CO2 affinity of RTILs, studies within membrane science have investigated the application of RTILs as a major component in gas separations through a technology called supported ionic liquid membranes (SILMs). SILMs retain RTILs within a porous support and do not experience the evaporative loss of the retained RTIL due to the inherently negligible vapor pressure of RTILs. While RTILs are used in supported ionic liquid membranes (SILMs) for CO2 purification, they suffer from the RTIL leaching from the membrane support at operating pressures above 10 bar. The combining of BCPs with RTILs presents a potential solution addressing this limitation.

Herein, we investigate the influence of 1-ethyl-3-methylimidazolium thiocyanate [EMIM][SCN] on casting solutions and composite membranes made from the amphiphilic BCPs poly(2-(dimethylamino)ethyl methacrylate)-block-poly(styrene) (PDMAEMA-b-PS) and poly(ethylene glycol)-block-poly(styrene) (PEG-b-PS). We report that the addition of [EMIM][SCN] influences morphology of resulting membranes through dynamic light scattering (DLS) and field emission scanning electron microscopy (FE-SEM) experiments. We further explore the changes in membrane characteristics with the addition of IL to composite gas separation membranes through dynamic time-lag gas experiments. We report that the addition of 1mg/ml of [EMIM][SCN] to solutions of 10mg/ml of PDMAEMA-b-PS in toluene causes a measurable swelling of particles by one order of magnitude. In addition, we noted a morphological change in cross-sections of composite PDMAEMA-b-PS membranes from an amorphous domain in the neat cross-section to globular vessels at the nanoscale within the polymer network of a 20wt% [EMIM][SCN] loaded membrane. However, the presence of the [EMIM][SCN] did not improve upon the selectivity of CO2 in the time-lag experiments. We assessed the sealing of composite polymer membranes and SILMs through a rubberization technique of polymerizing poly(dimethyl siloxane) (PDMS) on the membrane surface to confirm the [EMIM][SCN] loaded composite membranes did not possess greater CO2 selectivity than neat composite membranes.

Recommended Citation

Knight, Charlie Brandon, "Amphiphilic Block Copolymer and Ionic Liquid Composite Materials for Biphasic Gas Separation Membranes" (2025). Electronic Theses and Dissertations. 3311.
https://egrove.olemiss.edu/etd/3311