Jeong-Yun Sun1,2, Xuanhe Zhao3, Widusha R. K. Illeperuma1, Ovijit
Chaudhuri1, Kyu Hwan Oh2, David J. Mooney, Joost J. Vlassak &
The authors of this communications reported the synthesis of a hybrid
hydrogel consisting of ionically crosslinked alginate and physically
crosslinked polyacrylamide. The ionic interactions of the alginate based
hydrogels occur between the carboxylic groups of mannuronic acid or
guluronic acid and a divalent cation, which in their case was calcium.
The acrylamide was polymerized with ammonium persulfate as the
initiator, N,N-methylenebisacrylamide as the crosslinker, and
N,N,N',N'-tetramethylethylenediamine as a crosslinker accelerator. By
mixing the alginate acrylamide together with initiators, crosslinkers,
and calcium sulfate slurry, the authors were able to make a hybrid
hydrogel. This gel could be stretched 20x their initial length, even
with 90% water. The deformation was shown to be recoverable, and a notch
cut into it was stable up until a critical stretch limit at which the
notch started to tear. The hybrid gel was also shown to have a higher
elastic modulus (29 kPa), which higher than the elastic modulus of each
of the components (17 kPa for alginate and 8 kPa for polyacrylamide).
The authors also probed the mechanism of deformation and recovery, and
believe it to involve unzipping and re-zipping of the ionic crosslinks.