Hyper-Cross-Linked Polymers with Sulfur-Based Functionalities for the Prevention of Aging Effects in PIM-1 Mixed Matrix Membranes

The instability of gas permeation rates over time inPIM-1-basedmembranes is one of the obstacles preventing the implementation ofthis technology on larger scales. The addition of porous materialsto the PIM-1 matrix is a known process to reduce aging effects inPIM-1-based membranes. Many porous solids of various chemical natureshave been tested, ranging from inorganic to inorganic-organichybrids to completely organic materials. Here, we report on the synthesisof two hyper-cross-linked polymers (HCPs) based on the diphenyl sulfidemonomer, synthesized in either dichloromethane at 35 degrees C or dichloroethaneat 78 degrees C. Two mixed matrix membranes (MMMs) were obtained fromthe addition of 3 wt % of either filler to PIM-1. Both the CO2 permeation rates and the CO2/N-2 selectivitywere measured for the pure PIM-1 membrane and for the two MMMs overa period of 400 days. PIM-1 exhibits a classic aging behavior withan 85% drop in the CO2 permeation rate with respect tothe initial value. For the two MMMs, a retention of 50% of the initialCO(2) permeability was instead observed after more than 400days of aging. Despite the low surface area and low pore volume ofthe fillers, we show that diphenyl sulfide-based HCPs can reduce theaging rate in PIM-1 membranes.