POLYIMIDE, POLYIMIDE POLYMER ELECTROLYTE MEMBRANE, MEMBRANE ELECTRODE ASSEMBLY, AND SOLID POLYMER FUEL CELL

The present invention provides a novel polyimide containing a diamine component that has a fluorene skeleton having a sulfonic acid group or a derivative thereof, and a novel polyimide-based polymer electrolyte membrane containing this polyimide as a main component and having properties based on this polyimide (for example, a good balance between the resistance to methanol crossover and the proton conductivity). The polyimide of the present invention contains a structural unit (P) represented by the following formula (1). The polymer electrolyte membrane of the present invention contains this polyimide as a main component.