(45d) Influence of Poly(amic-acid) Coated Silver Nanoparticles on Membrane Selectivity and Stability: Unraveling the Optimal Loading Using Energetics of Gas Transport

Facilitated transport membranes (FTM) show superior performance over conventional polymer membranes over a short time frame, as they are susceptible to rapid performance decline due to photo/chemical aging. Additionally, the creation of mixed membranes (MMMs) by integrating silver nanoparticles and silver salts with polymer materials often leads to structural imperfections at the metal-polymer interface, diminishing selectivity. To address these challenges, a series of poly(amic- acid)s (PAAs) exhibiting systematically varied molecular weight/length and ether groups concentration were synthesized and used to fabricate, via the chelating-mechanism, silver nanoparticles in attempts to simultaneously i) achieve defect-free mixed matrix membranes (MMMs), ii) target CO2/CH4 and ethylene/ethane selective transport, and iii) reduce photochemical induced degradation. Individual and un-aggregated PAA-chelated silver nanoparticles were obtained and incorporated into a commercial polymer, Pebax 1657, to fabricate defect-free mixed matrix membranes.

The effect of the particle weight loading (0-4 wt%), and the PAA chain length on the structure and performance of the resulting MMMs was systematically investigated. Remarkably, inclusion of only 2.5 wt% nanoparticles in Pebax 1657 enhanced CO2 and ethylene permeability by 50% and 100%, respectively, whilst increasing both CO2/CH4 and ethylene/ethane selectivity between 80-100% relative to neat polymer. A detailed analysis of the transport mechanism and underlying energetics, as well as changes in thermo-mechanical properties was performed to elucidate the molecular origin of the observed membrane performance, as well as an apparent maximum in selectivity with silver weight loading. Finally, the newly synthesized materials were exposed to hydrogen over the course of 1,000 hours, to assess the long-term chemical stability of these materials.