Hyper-Cross-Linked Polymers with Sulfur-Based Functionalities for 2 the Prevention of Aging Effects in PIM‑1 Mixed Matrix Membranes

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