Swelling of Ultrathin Molecular Layer-by-Layer Polyamide Water Desalination Membranes
Edwin P. Chan, Allison P. Young, Jung-Hyun Lee, Christopher M. Stafford
The water vapor swelling behavior of ultrathin crosslinked aromatic polyamide films, synthesized via molecular layer-by-layer deposition, is characterized via specular X-ray reflectivity. The results show that these films expand only along the thickness direction and their maximum swelling ratio can be controlled by the specific diamine monomer chemistry. By measuring the swelling ratio as a function of water activity, the network parameters (Flory interaction parameter and monomer units between crosslinks) of these polyamides are characterized using the classical Flory-Rehner and the Painter-Shenoy thermodynamic swelling models. Comparing the monomer units between crosslink calculated from the swelling theories with values obtain from chemical analysis show that the Painter-Shenoy model gives a more accurate description of the polyamide networks investigated.