Abstract
Water vapor removal is a crucial process for several industries (e.g., air conditioning systems, flue gas dehydration, compressed air drying etc.). An effective dehumidification has the potential to drastically reduce the energy consumption and the overall cost of a process stream. Membranes with high water permeance and selectivity are promising candidates to achieve an energy-efficient water removal. We propose self-assembled membranes with interconnected and ordered hydrophilic domains that act as extremely fast water transport highways (water channels). We used a commercial amphiphilic pentablock copolymer (Nexar™), which has the ability to form long-range, self-ordering nanoscale morphologies with rigid end-blocks and a flexible molecular network where polar and non-polar solvents regulated the final morphologies of the membranes. Our results demonstrate how well-defined periodic morphology allow for molecular level control in effective removal of water vapor. The membranes with ordered hydrophilic nanochannels present a 6-fold improvement in water vapor permeability and a 14-fold increase in water vapor/N2 selectivity compared to Nexar™ membranes with disordered domains.
Molecular dynamics stimulations are carried out on the self-assembly behavior of block copolymer solution in different solvents. In addition, sorption and desorption kinetics studies for Nexar™ films were correlated to the different morphologies imaged by transmission electron, atomic force and environmental scanning electron microscopy.
Block copolymer membranes with ordered and disordered nanostructure showing highways for water molecules. [Display omitted]
•The Nexar nanoscale morphology was optimized for maximum water permeance.•The water vapor permeance of commercial Nexar films could be increased by 500%.•The water vapor selectivity could be increased 14 fold by optimizing the morphology.•Performance enhancement is explained using molecular dynamics simulations.
