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

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 Fourier-transform 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.