Controlling the Porosity of Starch Hydrogels with Poly(Methyl Methacrylate) (PMMA) Beads

Starch is a natural, biodegradable polymer that can be used to prepare hydrogels with various applications in food, pharmacy, medicine, agriculture, etc. In this study, a method of preparation using poly(methyl methacrylate) (PMMA) beads to control the porosity of starch hydrogels is proposed. The hydrogels are crosslinked with trisodium trimetaphosphate and dried in a vacuum oven. Results show that increasing the amount of PMMA beads result in higher porosity hydrogels ranging from ≈35% for hydrogels where no PMMA beads are used to ≈88% for hydrogels where the mass ratio of PMMA beads to starch is 10:1. Higher porosity hydrogels have a higher equilibrium water content and swelling degree, but lower mechanical properties. All hydrogels have a low solubility (<≈5%) and a high gel fraction (>≈90%) percentage. Upon degradation in α‐amylase at 37 °C, low porosity hydrogels (prepare with 0:1 and 1:10 PMMA beads:starch) degrade within 30 min, while high porosity hydrogels (prepare with 1:1 and 10:1 PMMA beads:starch) degrade within 3 weeks. The release of a dye that is incorporated into the hydrogel walls follows similar kinetics. Therefore, the use of PMMA beads is an efficient method to control starch hydrogel's porosity and properties.