Abstract
A challenge in the design of polymeric membranes for gas separation is the tradeoff between permeability, or how fast gases can flow through the membrane, and selectivity, the ability to separate one gas from another. In general, the more selective the membrane, the more slowly gases can flow through it. Sandru et al. overcame this tradeoff through a layered design. They used a bottom layer of porous polyacrylonitrile that acts as a physical support for the middle layer of either elastomer-like polydimethylsiloxane or glassy-type polytetrafluoroethylene. The authors then grafted a patchy layer of polyamine, which selectively attracts carbon dioxide, thus pulling it into the membrane and leading to much higher separation from nitrogen.