Conformational and solvent effects in structural and spectroscopic properties of 2-hydroxyethyl methacrylate and acrylic acid

2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) are monomers widely used in the production of hydrogels with medium-high water content. The structural and spectroscopic properties of HEMA and AA were studied using a combination of computational strategies based on both density functional theory (DFT) calculations and molecular dynamics (MD) simulations. DFT calculations have confirmed the co-existence of two stable HEMA conformers, while solute-solvent interactions between HEMA and AA with water were characterized by the analysis of MD simulations carried out by employing four different water models and different simulation conditions. The carbonyl and hydroxyl oxygen atoms of HEMA are involved in hydrogen bonding, whereas the ester oxygen atom does not appreciably interacts with the solvent. No significant differences in solute-solvent interactions are found between the two HEMA conformers. Their spectroscopic properties were calculated and the results were compared to experimental data. Although electronic spectra do not really allow a differentiation of the conformers, IR spectra present some peculiar bands to discriminate the presence and obtain information on the ratio of the conformers in solution. To verify the influence of a solvent with higher dipole moment on chemical properties, acetonitrile has been considered as an alternative solvent.