Water sorption in polymer network films synthesised from PEO oligomers containing acrylic and vinyl ether functionalities

Poly(ethylene oxide) oligomers, with end groups that have either acrylic or vinyl ether functionalities, were photopolymerised by UV radiation to crea te polymer networks in the form of thin films. Moisture sorption of the pol ymers, determined by microgravimetric analysis, was correlated to the oligo mer structure, i.e. to the PEO chain length and to the type of unsaturation . The data can be described with a Fickian diffusion model using diffusion coefficients of water in the polymer networks on the order of 1 x 10(-12) m (2)/s. The total amount of water sorption at equilibrium saturation increas es with an increasing number of EO units in the oligomer used to synthesise the network. The number of absorbed water molecules associated with each EO unit increas es with the number of these units in the oligomer until it reaches two wate r molecules per EO unit, for acrylated-PEO oligomers (PEGDA) having at leas t 30 EO units. The type of interactions between the polymer network and wat er were evaluated by means of thermal analysis performed on the hydrated fi lms. It was found that all water is present as bound rather than mobile wat er.