κ-Carrageenan Associated with Fructose/Glycerol/Water LTTM: Toward Natural Thermosensitive Physical Gels

Abstract

κ-Carrageenan was combined to a natural low-transition temperature mixture composed of fructose, glycerol, and water in a 1:1:5 molar ratio (FGW) to generate fully biobased physical gels through a simple method. The resulting gels can be easily prepared in various shapes. As for their hydrogel analogues, the rheological characterization of FGW-based samples evidenced thermosensitive gelation, attributed to the formation of aggregated H-bonded helices composed of κ-carrageenan chains. FGW-based gels exhibit a gel–sol transition temperature (Tg/s) higher than the one of hydrogels with recoverable and reversible viscoelastic properties upon successive heating/cooling cycles. SAXS analysis revealed a more extended conformation of chains in FGW that leads to more physical cross-linking junction zones within the materials. Such peculiar spatial internal organization provides a mechanical reinforcement demonstrated by compression tests. In conclusion, the use of the FGW solvent allows for designing κ-carrageenan physical gels with enhanced thermal and mechanical properties.