Swelling of thin polymer films: understanding the mechanisms and dynamics

Thin polymer films applied in organic solvent applications, such as coatings or thin selective membrane layers often show a decline in their performance over a period of time, making them unsuitable for long-term applications. The reason for this decline in performance can often be attributed to the swelling and instability of thin polymer films in organic solvents. At this moment there is still a poor understanding of the mechanisms behind the swelling and instability of high-performance polymers when in contact with an organic solvent and how these mechanisms change over time. As a result, predictions on the performance of thin polymer films in organic solvent applications are limited, preventing significant improvements in the membrane performance. The work described in this thesis provides a contribution to the understanding of the swelling dynamics of thin polymer films exposed to an organic solvent. This thesis discusses fundamental aspects, such as the accuracy of spectroscopic ellipsometry with respect to in situ thin polymer film swelling. Also, the swelling mechanisms and dynamics in glassy polymers are discussed using spectroscopic ellipsometry and broadband dielectric spectroscopy as measurement tools. More towards membrane applications, this thesis describes the swelling of a new potential barrier material, poly(PDMS-POSSimde) and reveals an underlying cause of membrane failure of polysulfone-based desalination membranes in water-toluene mixtures.