In Situ FT‐IR Spectroscopy Investigation of the Water Sorption of Amphiphilic PDMS Crosslinked Networks

Abstract

An amphiphilic poly(dimethyl siloxane) (PDMS) network is obtained by incorporation of poly(ethylene glycol) hydrophilic side chains within the hydrophobic matrix with the objective of improving the water affinity characteristics of the unmodified PDMS network. Sorption of water as a function of relative pressure of water vapor is investigated by in situ Fouriertransform infrared (FT-IR) spectroscopy. This experimental technique supplies information on the molecular interaction established between the penetrant and the polymer substrate and identifies the occurrence of self-association between water molecules (clustering). Self-association of penetrant increases with the concentration of water in the amphiphilic network. The overall diffusivity slightly decreases with increasing water concentration, likely due to the clustering effect. The maximum amount of water sorbed at equilibrium is low (<0.3 wt%), but significantly larger than that of the unmodified network.

Directly Probing Polymer Thin Film Chemistry and Counterion Influence on Water Sorption

“…11 Similar measurements have also been employed to understand water sorption on amphiphilic polydimethylsiloxane cross-linked networks with various poly-(ethylene glycol) hydrophilic side chain contents. 12 However, both of these studies rely on the use of gravimetric methods to determine actual sorbed water concentrations. Operating at reflection geometries, the so-called attenuated total reflection IR (ATR-IR) spectroscopy enables the ability to see signals arising from both adsorbed water and the hydrated polymer while avoiding an intense IR absorption from bulk water.…”

“…Although water sorption is critical in tuning these properties of polymeric materials, a direct quantification of the equilibrium amount of sorbed water is missing. Previous reports to indirectly measure water sorption were either solely based on gravimetric measurements or used gravimetric measurements to convert spectroscopic data to absolute values. − The techniques that are currently used to study water adsorption/sorption chemistry include spectroscopies, such as infrared (IR) spectroscopy, vibrational sum-frequency generation (SFG), and ambient pressure X-ray photoelectron spectroscopy (APXPS), and those that study structures include scattering and diffraction techniques. For hydration studies, IR spectroscopy, inherently a bulk-sensitive technique, is used to follow the O–H stretching band region because the interaction with water occurs through hydrogen bonding.…”

“…Time-resolved measurements showed that the intensity for the O–H stretching band of water sorbed in the films increased gradually on contact with water vapor at 50% relative humidity (RH) . Similar measurements have also been employed to understand water sorption on amphiphilic polydimethylsiloxane cross-linked networks with various poly­(ethylene glycol) hydrophilic side chain contents . However, both of these studies rely on the use of gravimetric methods to determine actual sorbed water concentrations.…”

Professor Yusuf Yagci at the Age of 65: Still Far Away from Retirement

“…Filip Du Prez employed thiolactone chemistry as a powerful tool for the formation of complex multifunctional architectures such as multifunctional dendrimer . Giancarlo Galli's group investigated the water sorption of the amphiphilic poly(dimethyl siloxane) cross‐linked networks containing poly(ethylene glycol) (PEG) hydrophilic side chains using in situ FT‐IR technique . In a following paper, Markus Antonietti and coworkers studied the one‐pot synthesis of main‐chain imidazolium‐containing polymers, some of which show unusually high thermal stability .…”