The Microstructure and Swelling Properties of Poly Acrylic Acid-Acrylamide Grafted Starch Hydrogels

Starch grafted acrylic acid-acrylamide hydrogel was synthesized using an aqueous solution polymerization method. The microstructures of the vacuum-dried hydrogel (VDH) and vacuum-freeze-dried hydrogel (VFDH) were studied by means of scanning electron microscopy and biomicroscopy. The water-absorption rate of the hydrogel was tested. The results showed that the microstructure of the two kinds of dried hydrogels exhibited significant differences. Before absorbing water, VDH had a relatively dense surface whereas the surface of VFDH had a clear macroporous structure. After absorbing water, a three-dimensional network structure was clearly visible in VDH. Many interlaced and free filaments occupied the space between the main skeleton and channels. The holes formed by vacuum-freeze-drying had the effect of squeezing the surrounding network structure, which had an impact on the water-absorption rate and water absorbency of the hydrogel.