Facile Fabrication of Thermosensitive Hydrogel Microspheres Based on a Combination of Metal-Free Click Chemistry and Spray Drying

In this study, thermosensitive hydrogel microspheres were fabricated by green, one-step spray drying, in which crosslinking points were formed in situ via a metal-free 1,3-dipolar cycloaddition click reaction. First, terpolymers were synthesized by the free radical copolymerization of hydroxyethyl methacrylate, N-isopropyl acrylamide, and N, N-dimethylacrylamide in a solution of 1,4-dioxane with 2,2-azobis(2-methylpropionitrile) as an initiator. Second, polymeric dipoles and polymeric dipolarophiles were prepared by modifying the as-prepared terpolymers with azidoacetic acid and N-maleoyl alanine, respectively. Finally, the hydrogel microspheres were produced by spray drying after dissolving polymeric dipoles and polymeric dipolarophiles in water under optimized conditions, such as solution concentration, inlet temperature, and feeding speed. Swelling experiments indicated that the hydrogel microspheres possess thermosensitivity, in that their swelling ratios decreased with an increase in temperature and their response to temperature was reversible and repeatable. The strategy described here holds great promise for the preparation of hydrogel microspheres since spray drying is an established industrial process with rapid, cost-effective, continuous features, and the in situ formation of crosslinking points was based on the metal-free click reaction without the involvement of organic solvents or catalyzers.Graphical abstract

Source: Chemical Engineering and Processing: Process Intensification - January 11, 2019 Category: Chemistry Source Type: research