UV-induced cross-linking of poly(ethylene oxide) in aqueous solution

Hydrogels of high-molecular-weight poly(ethylene oxide) (PEO) have been obtained in situ by applying a very simple procedure that involves UV cross-linking of PEO in aqueous solution. The efficiency of the photoactivated cross-linking of thin layers of PEO in aqueous solution in the presence of (4-benzoylbenzyl) trimethylammoniurn chloride as a photoinitiator has been determined at room temperature and in a frozen state (-25 degreesC). It was found that the efficiency varies with the concentration of PEO solution, the molecular weight of PEO, and especially with the temperature. When the UV cross-linking was performed in the frozen state, porous hydrogels with very high yield of gel fraction (above 90%) and high cross-linking density were obtained. After drying the hydrogels, films of 50-150 mum thickness were prepared. The films swell extremely fast in water and act as asymmetric membranes.