Perfluorocyclobutyl Polymer Thin-Film Composite Membrane Plasticization By CO2

In this study, we performed measurements on perfluorocyclobutyl (PFCB) polymer thin film composite membranes to evaluate the influence of film processing conditions (PFCB concentration and coating speed), aging time, and heat treatments (annealing temperature, time, and cooling conditions) on CO₂ plasticization pressure. The thickness of the prepared films ranged from 10 nm to 80 nm. Thicker films prepared at higher PFCB concentration and coating speed, as well as films annealed at higher temperature and for longer time, exhibited higher plasticization pressure. To better understand the effects of processing conditions and film history on plasticization, we compiled and analyzed plasticization data available in the literature for a number of polymers and discovered that the plasticization pressure correlated positively with the quotient of tensile modulus to solubility coefficient. Next, we measured the tensile modulus of each PFCB thin film by AFM to determine if the correlation also holds for films of a single polymer type prepared and/or aged using different conditions. Finally, long-term (1000 h) CO₂ aging studies at pressures above and below the plasticization pressure of membranes prepared using identical conditions indicated that plasticization could accelerate physical aging. Findings from this work provide the foundation for improved production practices of PFCB-based membranes with enhanced resistance to plasticization and physical aging by CO₂.