Cellulose Nanocrystals from Native and Mercerized Cotton

Nanocelluloses occur under various crystalline forms that are being selectively used for a wide variety of high performance materials. In the present work, cellulose fibers (CF-I) were mercerized by alkaline treatment (CF-II) without molar mass variation (560 000 g/mol) and both were acid hydrolyzed, forming cellulose nanocrystals in native (CNC-I) and mercerized (CNC-II) forms. This work establishes detailed characterization of these two nanoparticles morphology (light and neutron scattering, TEM, AFM), surface chemistry (zetametry and surface charge), crystallinity (XRD, 13C NMR), and average molar mass coupled to chromatographic technics (SEC-MALLS-RI, A4F-MALLS-RI), evidencing variations in packing of the crystalline domains. The crystal size of CNC-II is reduced by half compared to CNC-I, with molar masses of individual chains of 41 000 g/mol and 22 000 g/mol for CNC-I and CNC-II respectively, whereas the same charged surface chemistry is measured. This fundamental analysis may give insight to new applicative development.

Co-nonsolvency in concentrated aqueous solutions of PNIPAM: effect of methanol on the collective and the chain dynamics

The polymer dynamics in concentrated solutions of poly(N-isopropyl acrylamide) in water/methanol mixtures is investigated using light and neutron scattering.

GENERALIZED VAN HOVE FORMULA FOR SCATTERING OF NEUTRONS BY THE NONEQUILIBRIUM STATISTICAL MEDIUM

The theory of scattering of particles (e.g., neutrons) by statistical medium was recast for the nonequilibrium statistical medium. The correlation scattering function of the relevant variables give rise to a very compact and entirely general expression for the scattering cross-section of interest. The formula obtained by Van Hove provides a convenient method of analyzing the properties of slow neutron and light scattering by systems of particles such as gas, liquid or solid in the equilibrium state. In this paper the theory of scattering of particles by many-body system was reformulated and generalized for the case of nonequilibrium statistical medium. A new method of quantum-statistical derivation for the space and time Fourier transforms of the Van Hove correlation function was formulated. Thus in place of the usual Van Hove scattering function, a generalized one was deduced and the result was shown to be of greater potential utility than those previously given in the literature. This expression gives a natural extension of the familiar Van Hove formula for scattering of slow neutrons for the case in which the system under consideration is in a nonequilibrium state. The feasibility of light- and neutron-scattering experiments to investigate the appropriate problems in real physical systems was discussed briefly.