Linear PEI‐based responsive hydrogels: Synthesis and characterization

Abstract

Two responsive PEI hydrogels (P1.5E and P2E) were synthesized through a click reaction using linear PEI polymers with different cross-linker contents (ethylene glycol diglycidyl ether-EGDE) and avoiding organic solvents.Through 13 C HRMAS NMR and DSC studies the presence of residual epoxy groups and different protonation states of the linear PEI segments in the hydrogel were detected. The swelling and rheological behavior was dependent on the cross-linking degree. The hydrogel with the lower cross-linking degree (P1.5E) presented higher swelling values, but it was less resistant to the deformation. Besides, the swelling capacity and the resistance to deformation were found to be dependent on the interchain repulsions and charge of the amine groups, which endowed the hydrogels with stimuli-responsive behavior to pH or ionic strength changes. For both hydrogels, the swelling capacity and rheological properties were inversely proportional and directly proportional to the pH increase, respectively. Both materials presented adsorption capacity for the azo dye methyl orange (MO) and Cu 2+ ions. The interaction of the materials with the pollutants was also dependent on the cross-linking degree, being P1.5E the one that presented higher sorption capacities. Furthermore, the hydrogels did not release toxic molecules, as assessed by lettuce seeds germination experiments.

Linear Polyethyleneimine-Based and Metal Organic Frameworks (DUT-67) Composite Hydrogels as Efficient Sorbents for the Removal of Methyl Orange, Copper Ions, and Penicillin V

“…Consequently, at pH = 4, the secondary and tertiary amine groups on the polymer were protonated, enabling the material to interact effectively with the negatively charged MO and PEN. As the pH increased, the amine groups in the polymer became deprotonated, leading to a reduced capacity for the hydrogels to interact electrostatically with the pollutant molecules [7].…”

“…In a previous research work, our group developed a pH-and ionic strength-responsive hydrogel based on linear polyethyleneimine hydrochloride (L-PEI•HCl) [7]. Although the material had high swelling and adsorption capacities, it exhibited poor resistance to deformation, which hindered its manipulation, affecting its applicability.…”

A gelatin-based ionogel with anti-swelling properties for underwater human physiological signal detection

“…Many efforts were made to solve the problem of hydrogels being prone to swelling, for instance, regulating the hydrophobic interaction and crosslinking density. 22–24 However, the hydrogel could acquire inferior mechanical properties merely by increasing the crosslinking density and adjusting the hydrophobic interaction, which limited the fatigue resistance, electrical conductivity and sensing properties in practical applications. 25,26 The double-network hydrogel consisted of a brittle, stiff first network and a ductile, soft second network.…”