Generalizations from Molecular Simulation of Polyimide and Copolyimide sub-structures for the Robeson Diagram

Separation of many commercially important gas pairs using membranes is a growing application in the separation industry due to the advantages of membrane processes over traditional ones, such as lower capital cost and energy consumption, smaller footprint, ease of process integration, and lower maintenance costs. Substantial efforts have been expended in the search for superior polymeric materials with high performance separation, and mechanical and thermal resistance. Mainly, aromatic polymers like polyimides have emerged as a prominent membrane material in the gas separation area. Due to their rigid structure, these polymers show outstanding physical properties and high separation performance close to the trade-off relationships for many gas pairs. The thermal, mechanical and separation properties of polyimides strongly depend on their chemical structure, specifically in that a slight modification in their chemical structure may often result in a significant change in properties. Thus the development of structure-property relationships for polyimides, i.e., the ability to predict permeability and selectivity from polymeric structural units, provides for guidelines for designing optimum membrane candidates with desirable end-use properties.MOE (Min. of Education, S’pore