(396q) CO2 Separation Performance of Poly(ionic liquid) Membranes Containing Branched and Cyclic Functionalities

A series of poly(ionic liquid) membranes featured various branched and cyclic functionalities were synthesized and evaluated for CO₂/N₂, and CO₂/CH₄ separation performance.   The membranes were formed via ultra violet-polymerization of various ionic liquid monomers.  By functionalizing one of more carbon positions within the imidazole ring, we show that isomeric monomers can have very different selectivity and permeability behaviors when they are used to form poly(ionic liquid) membranes.  The mechanisms behind this behavior may be a combination of free volume and polarity effects that can favor CO₂ separation.  These new insights into poly(ionic liquid) membrane design reveal that functional groups have impacts that are greater than the sum of their parts.  Polymers were analyzed via IR spectroscopy to determine the degrees of polymerization, and via scanning electron microscopy to observe surface features as well as polymer thickness.  Once formed, membranes were tested in an experimental system to analyze the permeability and selectivity of the membrane in regard to N₂, CO₂, and CH₄.