3.2. Synthesis of HEMA-Based Hydrogels

A HEMA monomer was initially purified using vacuum distillation prior to polymerization. Briefly, EGDMA (0.04 g) and AIBN (0.04 g) were dissolved in HEMA (9.92 g). The resulting solution was mixed for 30 min, injected into a square mold comprising two glass plates internally covered with a polypropylene sheet and separated by a 0.20 mm wide Teflon frame, and was heated at 90 °C for 5 h to allow for polymerization to take place. The samples were then removed from the molds and subjected to extensive dialysis. They were then placed in 400 mL of de-ionized water (changed three times daily), for 2 days, to remove any unreacted monomer and initiators. Subsequently, square hydrogels (10 mm × 10 mm × 0.24 mm) were cut from the square mold, immersed in boiling water for 15 min, and dried at 40 °C overnight.