New thermo associating polymers were designed and synthesized by grafting amino terminated
poly(ethylene oxide-co-propylene oxide) (PEPO) onto carboxymethyl guar (CMG) and carboxymethyl
tamarind (CMT). The grafting was performed by coupling reaction between NH2 groups of PEPO and
COOH groups of CMG and CMT using water-soluble EDC/NHS as coupling agents. The grafting efficiency
and the temperature of thermo-association, Tassoc in the copolymer were studied by NMR spectroscopy.
The graft copolymers, CMG-g-PEPO and CMT-g-PEPO exhibited interesting thermo-associating behavior which was evidenced by the detailed rheological and fluorescence measurements. The visco-elastic
properties (storage modulus, G’; loss modulus, G”) of the copolymer solutions were investigated using
oscillatory shear experiments. The influence of salt and surfactant on the Tassoc was also studied by rheology, where the phenomenon of “Salting out” and “Salting in” was observed for salt and surfactant,
respectively, which can give an easy access to tunable properties of these copolymers. These thermoassociating polymers with biodegradable nature of CMG and CMT can have potential applications as
smart injectables in controlled release technology and as thickeners in cosmetics and pharmaceutical
formulations.