Available plasma-ignited frontal polymerization approach toward facile fabrication of functional polymer hydrogels

We report a novel approach for quickly fabricating poly(NVP-co-NMA) hydrogels (NVP = 1-vinyl-2-pyrrolidone, NMA = N-methylolacrylamide) by using plasma-ignited frontal polymerization (PIFP). Frontal polymerization was initiated by igniting the upper side of the mixture with plasma. Once initiated, no additional energy was required for the polymerization to occur. We thoroughly investigated the influence of the molar ratios of NVP/NMA on the properties of poly(NVP-co-NMA) hydrogels via this PIFP approach. The swelling rate, swelling behavior, and morphology of polymer hydrogels prepared via PIFP were comparatively investigated on the basis of water contact angle, swelling measurement and scanning electron microscopy (SEM). Results show that the swelling property of poly(NVP-co-NMA) hydrogels depends on NVP/NMA molar ratios, and the swelling capacity of the hydrogels prepared using PIFP approach is superior to that obtained using traditional batch polymerization (BP) method. More interestingly, these hydrogels, able to absorb quantum dots (QDs), exhibit obvious switching effect via altering the process of swelling and deswelling, which can be developed as QD-based moisture sensor.