Poly ionic liquid cryogel of polyethyleneimine: Synthesis, characterization, and testing in absorption studies

Here, we report the synthesis of polyethyleneimine (PEI) cryogels for the first time via cryopolymerization technique. The crosslinking of amine groups on the branched PEI chains is accomplished with epoxy groups of glycerol diglycidyl ether (GDE) based on epoxy-amine reactions in excess water at 218 degrees C in about 16 h. Superporous PEI cryogels with pore sizes >100 mu m were shown to have very fast equilibrium swelling behavior, e.g., 10 s to reach maximum swelling in DI water. Furthermore, the synthesized PEI cryogels were exposed to anion exchange reaction after protonation by HCl treatments to generate PEI ionic liquid cryogels containing hexafluorophosphate, thiocyanate, dicyanamide, and tetrafluoroborate. It was also demonstrated that PEI cryogels modified with [PF6](-) absorbed 47.8 +/- 5.7 mg/g of bovine serum albumin (BSA). Moreover, PEI cryogels were shown to be very useful as simple filtration filling materials for the direct removal of organic dyes such as methyl orange (MO) and eosin Y (EY) from their corresponding aqueous solutions with 98.5 and 98.6% yields, respectively. The separation of methylene blue (MB) from MO and EY mixture by using PEI cryogels as column filler materials was also demonstrated. (C) 2016 Wiley Periodicals, Inc.