(750c) The Perfluoropolymer Upper Bound

Perfluoropolymers have fundamentally distinct thermodynamic partitioning properties compared to those of their hydrocarbon counterparts. However, current upper bound theory assumes hydrocarbon solubility behavior for all polymers, regardless of their chemical composition. In this work, the effect of variable solubility behavior on upper bound position is critically assessed for perfluoropolymers and hydrocarbon-based polymers. Based off distinct solubility relationships, theoretical perfluoropolymer upper bounds are established, showing a positive shift of the upper bound front for certain gas pairs, including N₂/CH₄, He/H₂, He/N₂, He/CH₄, and He/CO₂, as a result of beneficial solubility selectivity. The perfluoropolymer upper bounds are compared to currently available experimental data. Within the framework of the solution-diffusion model, the approaches of achieving solubility selectivity through the use of perfluoropolymers and improving diffusion selectivity through the use of rigid hydrocarbon-based polymers are compared for their impact on the upper bound position. This comparative analysis demonstrates the significant benefit that can be achieved by considering both the chemical and morphological features of solid-state macromolecules when designing membrane materials. Finally, promising future applications for perfluoropolymers are discussed and preliminary data exploring the effect of fluorination on sorption and diffusion is presented.