Polymer reaction engineering tools to tailor smart and superabsorbent hydrogels

Abstract

Experimental and theoretical tools to describe and tailor polymer network formation processes are here addressed. Although a special emphasis is given to the synthesis, characterization, and applications of smart and superabsorbent polymers, other networks with higher cross-linker contents are also prospected. Purely synthetic and cellulose-based hydrogels are both considered in this research. The reactor type (e.g., batch or continuous flow micro-reactor), polymerization process (e.g., bulk, inverse suspension, or precipitation polymerization), and polymerization mechanism (e.g., classic free radical polymerization or reversible deactivation radical polymerization RDRP) are highlighted as possible tools to change the morphology and the molecular architecture of polymer networks and hydrogels. The tailoring of cellulose-synthetic hybrid materials is also addressed through the use of RAFT-mediated polymer grafting. Case studies showing the applications of the synthesized materials are presented, namely, molecularly imprinted hydrogel particles for retention of aminopyridines, molecularly imprinted polymers for polyphenols, caffeine or 5-fluorouracil selective uptake/ release, as well as modified cellulose adsorbents for polyphenol retention. Cellulose-based hydrogels are also considered as possible vehicles for polyphenol-controlled release. The mechanisms of liberation of polyphenols from these materials are analyzed, namely, when supercritical CO2 is used in the hydrogel impregnation process