Session: 12-29-02: Mechanics of Soft Materials

Paper Number: 150425

150425 - Elucidating the Role of Ionic Liquids in Polymer Composites 

The increasing climate change issue emphasizes the need for effective CO₂ capture technologies. Polymeric gas separation membranes have shown promise in filtering CO₂ efficiently. In this talk, we will specifically focus on a group of polyamide ionene (PA-ionene) membranes with the spirobisindane (SBI) group incorporated, which induces high porosity, resulting in enhanced CO₂ permeability and selectivity compared to other gases. Meanwhile, these polymers can also self-heal when damaged, making them ideal candidates for carbon capture in harsh environments where severe mechanical damage and chemical degradation may occur over time, reducing the carbon capture capability. Moreover, our experimental results revealed that by adding ionic liquids (ILs), such as 1-benzyl-3-methylimidazolium bistriflimide ([BMIM+][TF2N-]), the polymer composites self-healed faster and showed significantly higher CO₂ permeability while having minimal impact on the selectivity of CO₂ against other gas molecules. Therefore, we investigated the effects of adding [BMIM+][TF2N-] ILs to SBI-PA-ionene polymers on their structural characteristics and SH and gas transport properties.

We utilized molecular dynamics (MD) simulations using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) to investigate the structural and physical properties of SBI-PA-Ionenes with varying IL concentrations. Non-equilibrium MD simulations, including the uniaxial and triaxial tensile tests, were conducted to characterize the mechanical behaviors of polymers, including SH efficiency. Our results revealed that a higher concentration of ILs softens the polymer composites while allowing for a higher SH speed, aligning with our experimental measurements. We also performed several sets of structural characterization, such as the calculation of free fractional volume (FFV), the radius of gyration (R_g), radial distribution function (RDF), and static structure factor (SSF), to understand how polymer structures changed due to ILs and how such a change determined their physical properties. Our simulated SSF was also used to compare our MD-simulated structures against our small-angle X-ray scattering (SAXS) spectroscopy results. Our simulated structure characterization informs us that the FFV decreases as IL concentration increases due to ILs filling in the pores enabled by the SBI components. However, interestingly, the added ILs do not significantly affect the polymer structures, resulting in negligible chain-to-chain interaction variation. On the other hand, the IL interactions strengthen as IL concentration increases, mainly because ILs fill out the pores caused by SBI, increasing IL density since the overall volume does not increase proportionally. Consequently, the strong IL interactions due to added ILs are mainly responsible for the enhanced SH performance. The higher CO₂ permeability is also because of the improved affinity between ILs and CO₂ molecules. Our study provides a comprehensive framework for general high-performance amorphous material advancement for a broader range of applications based on the understanding and protocols developed from the materials studied in this project, from initial material discovery to industrial-level applications.

 

Presenting Author: Fatemeh Sabokroozroozbahani University of Vermont

Presenting Author Biography: Fatemeh is a PhD student in the Department of Mechanical Engineering at the University of Vermont.

Authors:

Fatemeh Sabokroozroozbahani University of Vermont
Jason Bara University of Alabama
Jihong Ma University of Vermont