Functionalization of Hydrogels Based on N‐Isopropyl‐acrylamide and Cationic Surfactant Monomers upon Electrostatic Self‐Assembly

Abstract

Summary: Positively charged copolymer hydrogels based on N‐isopropyl‐acrylamide (NiPAAm) and a cationic surfactant monomer (surfmer) were functionalized upon electrostatic self‐assembly of functional organic or inorganic complex counterions in the gel. As cationic surfmers 11‐acryloylundecyltrimethylammonium bromide (AUTMAB) or 11‐methacryloyl‐undecyltrimethylammonium bromide (MUTMAB) were used. The hydrogels were prepared from a micellar aqueous solution of the surfmer and NiPAAm either upon 60Co‐gamma irradiation, or upon chemical cross‐linking using methylenebisacrylamide as cross‐linker and 1,4‐diaminobutane as accelerator. Electrostatic self‐assembly was facilitated utilizing the thermoresponsive swelling and shrinking of the hydrogel. Several examples of gel functionalization are described such as in‐situ preparation of Prussian Blue and Pd0 nanoparticles, and induction of fluorescent properties. The catalytic activity of the palladium‐containing gel was studied by investigating the reduction of 4‐nitrophenol (4‐NP) with sodium borohydride as a model reaction. Fluorescent gels can be prepared upon exchange of bromide against 1‐pyrenesulfonate ions in the gel.

Photoisomerizable and Thermoresponsive N‐isopropylacrylamide–Surfmer Copolymer Hydrogels Prepared upon Electrostatic Self‐Assembly of an Azobenzene Bolaamphiphile

“…In subsequent de‐swelling and swelling cycles surplus functional anions are removed from the gel. Using this method of functionalization, highly fluorescent gels23 and catalytically active gels24 were recently prepared.…”