Novel intrinsically microporous homopolymers and copolymers derived from PIM-1 monomers (5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethylspirobisindane and 2,3,5,6-tetrafluoroterephthalonitrile) with two additional monomers-tetrahydroxydinaphthyl and tetrafluorotetraoxide thianthrene-are reported as potential materials for membrane-based gas separations. The resulting copolymers prevent efficient space packing of the stiff polymer chains and consequently exhibit analogous behavior to that of PIM-1, the most widely reported polymer in this class of materials. In addition, the copolymerization provides high molecular weight copolymers and low polydispersity if the polymerization reactions were conducted at elevated temperature for an extended period of time. Detailed structural characterization of the new monomers and polymers was determined by H-1 and F-19 nuclear magnetic resonance spectroscopy (NMR). The thermal properties were detected by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Polymer free volume was calculated from the polymer density and specific van der Winds volume. Under the same testing conditions, the homopolymer containing thianthrene units and most of the analogous copolymers have an excellent combination of properties with good film-forming characteristics. The gas transport properties show higher selectivity for gas pairs such as O-2/N-2, CO2/N-2, and H-2/N-2, with a corresponding decrease in permeability compared to PIM-1. This work also demonstrates that significant improvements in properties may be obtained through copolymers of intrinsic microporosity (CoPIM)s. Furthermore, this work extends the spectrum of high molecular weight soluble PIMs beyond those reported previously.