1 INTRODUCTION Polymer-based separation membranes are frequently prepared from polymers which are in the glassy state at ambient temperature, such as from cellulose triacetate (CTA), poly[1-(trimethylsilyl)-1-propyne] (PTMSP), the archetypal polymer of intrinsic microporosity (PIM-1), Matrimid®, polyacrylonitrile (PAN), poly(ether imide) (PEI), poly(sulfone) (PSf), or Nafion.1-6 This, however, implies that the relaxation of the glasses, which causes changes in their properties and depends on...