Two series of homopolyimides based on oxydiphthalic anhydride and bisphenol A bisether-4-diphthalic anhydride were synthesized with 12 kinds of aromatic diamines. Several thermo-processable homopolyimides were the focus of further investigation. The structureproperty relationships of these homopolyimides were examined as functions of the glass transition temperature (T g ), melting point (T m ), thermal decomposition temperature (T d ), and meltflowability. The effects of the chemical and higher-order structures on these properties were discussed in this work to obtain an indication for the molecular design of high-performance thermoprocessable polyimides. A series of thermoplastic copolyimides were prepared to achieve higher T g and T d without sacrificing thermo-processability. The copolyimides investigated exhibited a comparable or lower melt viscosity, higher T g and T d , and higher long-term thermo-oxidative stability than those of ULTEM type polyimides. One of them exhibited a low melt viscosity (4700 poise at 400 • C), a high T g (224 • C), and excellent thermo-oxidative stability.

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Aromatic copolyimides were prepared using 2,3,3′,4′-biphenyltetracarboxylic dianhydride (asymmetric BPDA or a-BPDA) and several aromatic diamines with flexible ether linkages to obtain melt-processable polyimides (PIs) with balanced properties, i.e. high Tg, high thermo-oxidative stability, low melt viscosity, and sufficient toughness. The use of a-BPDA for the present purpose is based on our previous results which showed that a-BPDA-based PIs always show both higher Tg and much higher thermoplasticity than the corresponding symmetric BPDA-derived PIs. On the basis of the structure–property relationship, a copolyimide system was focused upon as a promising candidate. The molecular weight of the selected copolyimide was controlled using an end-capping reagent to balance between Tg, the melt viscosity, and toughness. The effect of the polymerization route (one-pot and two-step) on the properties was also discussed. An a-BPDA-based copolyimide accomplished a high Tg at 249 °C, a low melt viscosity of 8200 Poise at 400 °C, and high thermo-oxidative stability concurrently with considerably high film toughness (elongation at break = 66%).

A combination of grand canonical Monte Carlo (GCMC) and density functional theory (DFT) simulations was used to investigate the effect of modified metal center in ligand for CO 2 capture in novel Zr-based porphyrinic metal−organic frameworks (PCN-224-Ms, M = Mg, Fe, Co, Ni, Mn, and Zr). The results show that the MTCPP ligands (TCPP = tetrakis(4-carboxyphenyl)porphyrin) provide more favorable adsorption sites than the inorganic Zr 6 nodes for CO 2 molecules. The modification of metal center in MTCPP ligand has a remarkable effect on the single-component adsorption of CO 2 compared to CH 4 and thus enhances the adsorption of CO 2 and the selectivity of CO 2 over CH 4 . Furthermore, Coulomb interaction between adsorbate and framework plays a dominant role compared with non-Coulomb interaction in the process of adsorption and separation. Among various modified metal centers, the Zr-MTCPP is found to be the best for enhancing the adsorption and selectivity of CO 2 . In addition, a small amount of water has a negative effect on the selectivity of CO 2 /CH 4 , and its influence follows the order PCN-224-Zr > PCN-224-Mn > PCN-224-Ni, depending on the strength of Coulomb interaction between H 2 O molecules and frameworks.

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