Polyethylene‐Glycol‐Based Thermoreversible Biscarbamate Hydrogels and Metallogels Synthesized through Non‐Isocyanate Route

Abstract

AbstractIn this work, an isocyanate free approach has been adopted to synthesize hydroxy urethanes exhibiting self‐assembling properties. Polyethylene glycol (PEG) end capped with glycerol carbonate was subjected to aminolysis with aliphatic mono amines to yield bishydroxyl urethanes. The amphiphile thus obtained exhibited gelation in water to yield thermoreversible hydrogels. The hydroxyl groups of urethane bond initiated self‐assembly through intra and intermolecular hydrogen bonding between the secondary hydroxyl groups and amide group of the biscarbamate moiety and this was exemplified by Fourier transform infrared spectroscopy (FT‐IR) studies. Differential scanning calorimetry (DSC) revealed that gel melting temperatures are influenced by the length of aliphatic mono amines. Orientation of the gelator molecules and the mode of aggregation of molecules into sheets during the self‐assembly was confirmed by XRD studies and field emission scanning electron microscopy (FE‐SEM). Visco‐elastic properties of resulting PEG‐hydrogels were studied by rheology. In addition, incorporation of metal ions increased the mechanical strength and thermal stability, which was assisted by complex formation between the metal ions and gelator molecules. One of the metal ion responsive hydrogel was capable of entrapping vitamin B12 and the slow release of drug molecule triggered in acidic pH was demonstrated.