Preparation of Dense Polybenzimidazole Films without Organic Solvents

A new technique involving physical modification after polymerization was developed in which gel polybenzimidazole (PBI) membranes were converted into dense PBI films. Using the polyphosphoric acid (PPA) process, gel PBI membranes were prepared and underwent acid removal followed by a controlled densification step. PBI polymers with rigid PBI backbone structures, such as para-PBI, were prepared as dense films from high-molecular-weight polymers. This approach to produce dense PBI films from gel PBI membranes can allow for new PBI structures that exhibit little to no solubility in organic solvents to be produced as dense films and holds potential for various applications of PBI films. The technique also provided lower associated costs, time, waste generation, and energy consumption, compared to previous methods. The new process and properties of the resulting dense PBI films will be discussed.