Thermal studies of plant carbohydrate polymer hydrogels

Isolation and thermal analysis of hydrogels from Plantago ovata (PO), Salvia aegyptiaca (SA), Ocimum basilicum (OB) and Mimosa pudica (MP) are reported. The hydrogel obtained from PO was modified by cross-linking, carboxymethylation and ethylation as a model to see the effect of modification on thermal behavior. Activation energy, enthalpy, entropy, free energy change, pre-exponential factor, comprehensive index of intrinsic thermal stability (ITS) were determined from the thermograms. The ITS values indicated good thermal stabilities of the hydrogels. Hydrogels isolated from SA, OB and MP did not show significant differences in their thermal behavior, whereas significant differences in thermal profiles of PO gel and its modified forms were observed. The modified gels exhibited improved thermal stability. Formation of water, 2-hydroxybutanedial, 3-hydroxypropanal and 2-furfuryl alcohol as degradation products was detected in the GC–MS analysis of some of the materials. The possible implications of these results are discussed.