Thermal crosslinking and fabrication of poly (N-isopropylacrylamide) nanofibers

Abstract

To prepare thermo-responsive nanofibers with excellent stability and high sensitivity, the copolymer P (NIPAm-co-NMA) is synthesized by free radical copolymerization of N-isopropylacrylamide (NIPAm) and N-methylol acrylamide (NMA). Furthermore, the polymer is crosslinked via thermal treatment which results in highly cross-linked copolymer, thereby increasing the resistance to dissolution around lower critical solution temperature (LCST). In addition, the copolymer is electrospun into nanofibers. The influence of electrospinning condition on the morphology and diameter of the resulting nanofibers, and the effects of thermal treatment temperature and duration on the degree of cross-linking and morphology retaining ability are systematically investigated. The results show that the optimal spinning conditions are as follows: the polymer concentration is 10% and the spinning voltage is 10 kV. The optimal thermal cross-linking temperature is 130 ℃ and the treatment duration is 6 h. The degree of cross-linking of the as-obtained fibers is 82%. The fibers after thermal cross-linking could maintain the stability in water at a low temperature. After 5 cycles of heating-cooling, the fibers could retain 98% of the initial weights.