Development of a double-network ion gel membrane composed of a CO2-philic ionic liquid, semi-crystalline polymer network, and tetra-armed polyethylene glycol network

We developed a tough ion gel membrane containing a large amount of CO2-philic ionic liquid (IL) in accordance with the toughening principle of double-network gels. Pebax 1657, which is composed of a semicrystalline polyamide block, was used as the first network in the ion gel membrane. It formed a sacrificial-bond network that dissipated the loaded energy. We interpenetrated the Pebax 1657 network with tetra-PEG hidden-length network, which is highly stretchable and compatible with the CO2-philic IL 1-ethyl-3-methylimidazolium tricyanomethanide. This enhanced the fracture strain of the ion gel membrane and increased the energy dissipated by the Pebax 1657 network. The high mechanical strength enabled the developed ion gel membrane to retain 92.5 wt% of the IL and provide a top-tier CO2 separation performance: the ion gel membrane exhibited a CO2 permeability and CO2/N-2 permselectivity of 3100 barrer and 43, respectively. The CO2 permeability of the ion gel membrane increased with increasing relative humidity without compromising the CO2/N-2 permselectivity. The CO2 permeation property was maintained for more than 10 days under a relative humidly of 80 % at 80 degree celsius. The stable CO2 separation performance of the ion gel membrane satisfies the standards requirements for CO2 capture from flue gases released by coal-fired power plants.