By taking the advantages of high permeability characteristics of carboxylated PIM-1 (cPIM-1) and high selectivity properties of P84, a new type of cPIM-1/P84 blend membranes has been designed in this study for pervaporation dehydration of isopropanol and CO2/CH4 separation. P84 is known to be a highly selective polyimide with low permeability for alcohol dehydration and gas separation, while cPIM-1 is a highly permeable PIM-1 modified via hydrolysis reaction. Polarized light microscopy was employed to study their homogeneity. It was found that the P84/cPIM-1 blends were fully miscible when either cPIM1 or P84 content was at or lower than 10 wt%. The molecular-level interactions were further confirmed by FTIR and DSC. The cPIM-1 loading has significant impact on sorption and diffusion of water and IPA in blends, as indicated by vapor sorption tests. The pervaporation dehydration of isopropanol (IPA) shows that the incorporation of only 10 wt% cPIM-1 in the P84 matrix enhances the water permeability by 87% without compromising its selectivity. It has an IPA/water selectivity of 6263 and a water permeability of 0.0864 mg m(-1) h(-1) Kpa(-1). Similarly, the addition of 30 wt% cPIM-1 into P84 increases the CO2 permeability by 430% from the original 1.3 to 6.98 Barrers. The P84/cPIM-1 membrane containing 90% cPIM1 has the CO2/CH4 separation performance surpassing the Robson upper bound. The newly developed compatible cPIM-1/P84 blend membranes exhibit great potential for the applications of alcohol dehydration and gas separation. (C) 2016 Elsevier B.V. All rights reserved.