Polyacrylamide cryogels by photoinitiated free radical polymerization

A novel method for the preparation of poly(acrylamide) cryogels by photoinitiated polymerization of monomeric precursors was described. A series of poly(acrylamide) cryogels were easily prepared by irradiating aqueous solutions containing acrylamide and N,N′-methylene(bis)acrylamide as monomer and cross-linker, respectively, in the presence of 1-[4-(2-hydroxyethoxy)phenyl]-2- hydroxy-2-methyl-1-propane-1-one (Irgacure 2959) as water-soluble photoinitiator with the help of freezing-thawing procedures. Photolysis was conducted at -13 °C isothermally through specially designed cryostat-integrated Rayonet merry-go-round photoreactor. On comparing the described photochemical method with the conventional redox counter part, the polymerization is initiated, and gelation proceeds only on external stimulation by light. This way, concomitant hydrogel formation usually observed with the redox process as a result of premature polymerization during the cooling process was prevented. The obtained cryogels exhibited superfast swelling behavior.