Thermal stability, swelling behavior and CO2 absorption properties of Nanoscale Ionic Materials (NIMs)†
Nanoscale Ionic Materials (NIMs) consist of a nanoscale core, a corona of charged brushes tethered on the surface of the core, and a canopy of the oppositely charged species linked to the corona. Unlike conventional polymeric nanocomposites, NIMs can display liquid-like behavior in the absence of solvents, have a negligible vapor pressure and exhibit unique solvation properties. These features enable NIMs to be a promising CO2 capture material. To optimize NIMs for CO2 capture, their structure–property relationships were examined by investigating the roles of the canopy and the core in their thermal stability, and thermally- and CO2-induced swelling behaviors. NIMs with different canopy sizes and core fractions were synthesized and their thermal stability as well as thermally- and CO2-induced swelling behaviors were determined using thermogravimetry, and ATR FT-IR and Raman spectroscopies. It was found that the ionic bonds between the canopy and the corona, as well as covalent bonds between the corona and the core significantly improved the thermal stability compared to pure polymer and polymer/nanofiller mixtures. A smaller canopy size and a larger core fraction led to a greater enhancement in thermal stability. This thermal stability enhancement was responsible for the long-term thermal stability of NIMs over 100 temperature swing cycles. Owing to their ordered structure, NIMs swelled less when heated or when they adsorbed CO2 compared to their corresponding polymers.