Facile synthesis of 4-vinylpyridine-based hydrogels via laser-ignited frontal polymerization and their performance on ion removal

We report herein the fabrication of poly(AAM-co-4VP) hydrogels (AAM = acrylamide, 4VP = 4-vinylpyridine) by using laser-ignited frontal polymerization (LIFP) in an easy and rapid way. The appropriate amounts of AAM, 4VP, gamma-methacryloxypropyltrimethoxysilane-modified nanosilica, and couple redox initiator of ammonium persulfate/N,N,N',N'-tetramethylethylenediamine were mixed together in the presence of dimethylsulfoxide as solvent. LIFP was initiated by heating the upper side of the mixture with the laser. Once initiated, no further energy or treatment was required for the following polymerization to occur. A variety of features for the preparation of hydrogels, such as the initiator concentration and the ratio of different monomers, were thoroughly investigated. The morphology and swelling behavior of hydrogels were investigated. For comparison, the hydrogels prepared via traditional thermal frontal polymerization were also presented and discussed. Furthermore, the hydrogels possess absorption capacity towards copper ions, which can be applied to remove heavy metals.