Solid-state NMR Studies Of Thermo-sensitive Cellulose/Poly (N-isopropylacrylamide) Composite Hydrogel

In this work, the natural cellulose was used as raw material, it was dissolved in 7 wt% NaOH/12 wt% urea solution at the temperature of-12 ℃. And then the cellulose solution was to become hydrogel through crosslink. The cellulose/Poly N--(isopropylacrylamide) (PNIPAM) composite thermo-sensitive hydrogel was prepared by interpenetrating polymer network (IPN) approach polymerization successfully. Its thermo--sensitivity could be characterized from DSC, UV-Vis, swelling ratio and its LCST was about 32 ℃.And my most important work was that various solid-state Nuclear Magnetic Resonance(NMR) methods were used to investigate this cellulose/PNIPAM composite hrdrogel material. The solid state NMR methods chose including 13C CP/MAS NMR、13C QCP NMR and static1H NMR which were carried to analyze the structure、content and property of the cellulose/PNIPAM composite hrdrogel; and static 1H NMR at different temperature and 1H filtering-spin diffusion NMR experiments were performed to analyze dynamics of the composite thermo-sensitive hydrogel. Test results show that the cellulose/PNIPAM composite hydrogels have good temperature sensitivity, and the LCST got from nuclear magnetic resonance (NMR) was consistent with results of thermodynamic test. Kinetics studies show that cellulose molecules mainly in exercise-induced lower rigidity condition, PNIPAM mainly in the motility of the flexible state; When temperature at the LCST, change of PNIPAN conformation made a significant reduction in the molecular motor; PNIPAM molecules under low motility curled up the motor still stronger than the cellulose molecules; Dipolar filter-spin diffusion research proves that motility of PNIPAM chain and cellulose molecular chain in cellulose/PNIAPM composite hydrogel can pass each other, so they have close space distance.