Study On The Interaction Of Components In Cellulose/NaOH/Urea Solution By NMR

Cellulose is abundant in nature and will be the main industrial materials in future. NaOH/urea aqueous solution is a novel and green solvent system and can dissolve cellulose rapidly. Cellulose materials,such as fibre, film, can be obtained from the cellulose solution. In this work, the dissolution mechanism of cellulose in NaOH/urea/H2O solution was studied using NMR. Through NaOH/urea aqueous solution, a series of cellulose/PVA composite films were prepared, which were proven to be have good blood compatibility property. In addition, aggregation behavior of poly nonylphenol polyoxyethylene ether (3NP-10) molecules in aqueous solution was studied by liquid NMR.The main results of this work are as follows:1. NMR technologies, which include 1H NMR、23Na NMR、1H DOSY and 13C DOSY experiments, were applied to study the interaction between the cellulose and the solvent components. Results show that parts of sodium hydrates attached to cellulose chains, prevent cellulose chains from self-aggregation. Parts of sodium hydrates form complicated complex with urea, distributed between the cellulose chains to isolate the chains form new hydrogen bond with each other. At low temperature, the hydrogen bond between Na+ hydrates and cellulose is not changed, but the hydration of solvents is increased, which isolated cellulose self-aggregated efficiently.2. By using alkali urea solvent, cellulose/PVA composite films was obtained. Structure of cellulose/PVA films were characterized by solid NMR.Results showed that PVA had no effect on the structure of cellulose and the stability of cellulose/PVA composite film was attributed to the hydrogen bond interaction between cellulose and PVA. Cellulose/PVA composite films show good mechanical property and good blood compatibility. Among all the cellulose/PVA composite films, the films prepared by freeze-thaw method show the best properties.3. By using some NMR techniques, molecular motion of hydrophobic alkyl chain and hydrophilic polyoxyethylene chains in the formation of macromolecular surfactant(3NP-10) micelles were studied. Results show that the translational motion of 3NP-10 molecules were relatively fast in the dilute solution and both the polyethylene glycol chains and the alkyl chains were relatively closed to each other; with the concentration increased, polyethylene glycol chains shrinked and closed to each other. At the same time, the hydrophilic polyoxyethylene chains enclosed the alkyl chain gradually,3NP-10 aggregated and formed micelle due to the polar interaction. The hydrophobic alkyl chain was situated internal in micellar core, and the motion of alkyl chain was restricted in the nonpolar environment. The hydrophilic polyoxyethylene chains stayed in the exterior of the micellar core and the motion of polyoxyethylene chains were relatively free in aqueous solution. With the increase of concentration, the micelles remained stable in a relatively wide concentration range.