Synthesis of Temperature Responsive Biohybrid Guar-Based Grafted Copolymers by Click Chemistry

Novel thermoresponsive biohybrid guar-based grafted copolymers were prepared in aqueous medium by copper catalyzed 1,3-dipolar Huisgen cycloaddition between an α-butoxy-ω-azido-PEO-co-PPO derivative, characterized by LCST behavior, and guar gum bearing alkyne functionalities randomly distributed along the chain. The chemical pathway gives well-defined guar-g-(PEO-co-PPO) copolymers with tunable chemical compositions. The resulting grafted copolymers were shown to exhibit a reversible thermo-induced association leading to elastic physical network-like behaviors. It has been shown that the rheological properties are intimately related to the molecular weight and to the degree of substitution of guar. The temperature of association of the grafted copolymer is controlled by the cloud point of the grafted polyoxyalkylene and the salt concentration variation appeared as a very convenient manner to tune the thermoresponsive character without changing the chemical nature of the side-chains. Finally, in relation w...