Water state in HEMA-based hydrogels: a theoretical and experimental investigation

The role of water in hydrogels attracts much attention for its influence on several properties. In this work, water states in hydrogel systems were investigated via both theoretical and experimental approaches. The work consisted in four major parts. First, the 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) monomers in solution were investigated concerning conformers stability and solute-solvent interactions, highlighting hydrogen bond descriptions. Second, physical poly-HEMA hydrogel systems, characterized by low molecular weight, were studied through molecular dynamics to distinguish water states in hydrogels, evaluate intermolecular and intramolecular interactions and investigate dynamical properties. Third, poly-(HEMA/AA) hydrogels at various water content were synthesized: with and without freeze-casting and with and without poly vinyl alcohol (PVA) as an anti-freezing agent, to evaluate the additive effect on water states, and physical poly-(HEMA/AA) hydrogel systems were then simulated to evaluate the AA effect on the hydrogel properties. Fourth, studies on high molecular weight hydrogels, considering both physical and chemical networks, were started for better describing real systems.