Glycerol as a green solvent for enhancing the formulation of dextran methacrylate and gellan-based semi-interpenetrating polymer networks

Recently, glycerol has been exploited in a number of industrial applications, thanks to its high availability, its low cost and, overall, its peculiar properties which fit well with the green chemistry principles. In this work, the ability of glycerol to solubilize high molecular weight polymers and to allow the formation of glycerol-based semi-interpenetrating polymer networks, called "gly-semi-IPNs", has been investigated. Compared to water, glycerol deeply affects the structural properties of the biopolymers, especially with reference to their chain flexibility. Among the polysaccharides, dextran methacrylate (DexMA) and gellan gum (Ge) were selected. Glycerol solutions of both polysaccharides and their mixtures, as well as a DexMA network (obtained by cross-linking in glycerol and in the presence of a photoinitiator), were rheologically characterized to assess the role of the solvent on the chain conformation and on the mechanical properties of the networks. Interestingly, glycerol was found to deeply influence the mechanical, morphological and optical properties of the formed hydrogels, as well as to improve the cross-linking kinetic of DexMA. Furthermore, glycerol leads to more homogeneous mixtures of the two polysaccharides than those observed in aqueous buffers. As such, novel gly-semi-IPNs, with enhanced formulation and mechanical properties, were prepared and characterized.