Effects of solvents on rheological and crosslinking properties of photo-polymerized poly(ethylene glycol) hydrogels

The effects of solvents such as water and ethanol on the rheological properties and crosslinking characteristics of poly(ethylene glycol) (PEG) hydrogels were examined. Real-time storage modulus data for pre-polymerized mixtures containing different solvents during the photo-polymerization process successfully explained the differences in the formation of crosslinked networks of the corresponding hydrogels. Various experimental methods for Fourier transform infrared spectroscopy (FT-IR), swelling ratio, Rhodamine-B (Rh-B) loading/release properties, and scratch/indentation depths on hydrogel surfaces, were employed to systematically compare macroscopic structural and mechanical properties of the crosslinked PEG hydrogels with different solvents (water and ethanol). The effects of the solvents on the hydrogel properties were satisfactorily consistent, and the results clearly indicated that water hindered the formation of the crosslinked network more severely than ethanol at the same weight ratio because of the presence of larger number of water molecules in pre-polymerized mixtures, which was a more favorable feature for water than ethanol in the initial crosslinking growth.