Facile Glycerol-Assisted Synthesis of N-Vinyl Pyrrolidinone-Based Thermosensitive Hydrogels via Frontal Polymerization

We report a facile strategy for quickly fabricating thermosensitive poly(HPMA-co-NVP) hydrogels in the presence of glycerol by using frontal polymerization (FP). The appropriate amounts of hydroxypropyl methacrylate (HPMA) and 1-vinyl-2-pyrrolinone (NVP), N,N'-methylenebisacrylamide (MBAA), and ammonium persulfate (APS)/N,N,N',N'-tetramethylethylenediamine (TMEDA) couple redox initiator were mixed together at ambient temperature in the presence of glycerol as the medium. A variety of features for preparing hydrogel samples, such as ratios of NVP/ HPMA, the presence of the glycerol and its concentration, and MBAA cross-linker concentration, were thoroughly investigated. We have found that the presence of glycerol can suppress the fingering of FP and overcome the formation of bubbles. Also, the ratio of NVP/HPMA for synthesis of hydrogels by FP plays ail important role in its microstructure and swelling property. The morphology, thermosensitive behavior, and swelling studies of polymer hydrogels prepared via FP are comparatively investigated on the basis of environmental scanning electron microscopy (ESEM) and swelling measurement. Results show that the swelling capacity of the hydrogel prepared via FP is superior to that obtained by the traditional batch polymerization (BP) method. The glycerol-assisted FP can be exploited as ail alternative means for synthesis of NVP-based copolymer hydrogels with additional advantages of fast and efficient way.