Molecular Basis for Solvation Structure and Thermodynamics of Polyacrylamide in Aqueous Solutions of Glucose

High Resolution Image Download MS PowerPoint Slide Polyacrylamide (PAAm) exhibits distinctive properties that find applications in biomedicine, environmental engineering, and material science. PAAm is used in wastewater treatment and in the cosmetic industry, besides being an important matrix for gel electrophoresis. Nonionic solutes, such as sugars, significantly influence the stability, structural dynamics, and solvation properties of PAAm. One particularly interesting interaction is that of PAAm with glucose in aqueous solutions. Experiments show that PAAm is preferentially hydrated, yet the increase of glucose concentration causes the swelling of PAAm gels. Here, we use molecular dynamics simulations to understand the structure and thermodynamics of PAAm solvated by aqueous glucose solutions. The polymer is effectively preferentially hydrated at all glucose concentrations, but nevertheless, significant glucose–polymer interactions exist. PAAm conformations are correlated with the solvent organization, with extended structures displaying regular solvation patterns that are partially lost for globular polymer arrangements. Interestingly, glucose subtly favors specific dihedral conformations of PAAm, which are consistent with polymer extension and possible swelling within the extent experimentally observed. The study of the structure and thermodynamics of PAAm was possible with Minimum-Distance Distribution functions (MDDFs), which provide a versatile representation of the solvent organization independently of the complexity of the solute shape, illustrating for the first time their utility in analysis of the solvation of a polymer in a random coil conformation.