Preparation and gas separation properties of spirobisbenzoxazole-based polyimides

Improving the processability and permeability of aromatic polyimides is a prerequisite for promoting the application in the field of gas separation membranes. Here, a series of novel spirobisbenzoxazole-based polyimides were synthesized. The novel spirobisbenzoxazole unit showed a larger rigid step size than the reported spirobisindane unit, which more effectively destroyed the molecular packing. As a result, the obtained aromatic polyimides showed good organic solubility and significantly improved gas permeability. Such polyimides were also considered as polymers of intrinsic microporous (PIMs) with ultra-micropore distribution of 5 similar to 7 angstrom and high BET surface areas ranging from 373 to 449 m(2)/g. Meanwhile, the obtained polyimide membranes exhibited excellent thermal properties (T-g > 400 C) and outstanding mechanical properties (sigma > 100 MPa). The effects of rotation restriction and thermal annealing process on gas permeation behavior were also studied.

Automated summary

A series of novel spirobisbenzoxazole-based polyimides were synthesized, which exhibited good organic solubility, improved gas permeability, ultra-micropore distribution and high BET surface areas, as well as excellent thermal and mechanical properties. The effects of rotation restriction and thermal annealing process on gas permeation behavior were also studied.