Effect of Backbone Rigidity on the Glass Transition of Polymers of Intrinsic Microporosity Probed by Fast Scanning Calorimetry

Polymers of Intrinsic Microporosity (PIMs) of high performance have developed as materials with a wide application range in gas separation and other energy-related fields. Further optimization and long-term behavior of devices with PIMs require an understanding of the structure-property relationships, including physical aging. In this context, the glass transition plays a central role, but with conventional thermal analysis a glass transition is usually not detectable for PIMs before their thermal decomposition. Fast scanning calorimetry provides evidence of the glass transition for a series of PIMs, as the time scales responsible for thermal degradation and for the glass transition are decoupled by employing ultrafast heating rates of tens of thousands K s(-1). The investigated PIMs were chosen considering the chain rigidity. The estimated glass transition temperatures follow the order of the rigidity of the backbone of the PIMs.