Design and synthesis of polyimides with high internal free volume elements

Abstract

Tuning of free volume element distributions and sizes in glassy polymers is technologically important because of their lots of usefulness in microelectronics (e.g., low-k dielectic materials), gas storage (e.g., organic adsorbents) and separation technology (e.g., high permeable and selective membrane materials). Here we show that the material design using a 3-dimensional rigid structure having internal void space can create a number of free volume elements in semirigid, or rigid glassy polymers. To achieve it, a triptycene-based monomer was synthesized for polymer material design and ester-acid chemical imidization polymerization was used for high molecular polyimide. Thanks to internal free volume in rigid structure, the resultant polymer exhibits high glass transition temperature up to 350 oC, excellent thermal stability and good solution processibility due to good solubility in common organic solvents. As a polymeric membrane for gas separation, the triptycene-based polyimide shows good gas transport properties, high permeability and selectivity, and low CO2 plasticization in the mixed gas separation. We anticipate that this kind of polymer design provides keen insight on the development of processible thermoset polymers having fine microporous structures on sub-nanometric scales for high performance glassy polymer applications.