Silver Intercalation into Cellulose Matrix. An X-Ray Scattering,Solid-State 13C NMR,IR, X-Ray Photoelectron,and Raman Study

Diffusion of silver ions into a cellulose matrix and their subsequent reduction both with the matrix itself and with specific reducers lead to preparation of cellulose materials containing silver(0). Most silver metal is intercalated into the cellulose matrix when glycerol is used as solvent and potassium hypophosphite or sodium boron hydrate are used as reducers.     

The effect of drying method on the properties and nanoscale structure of cellulose whiskers

Cellulose whiskers were prepared from wood- and cotton-based microcrystalline cellulose and dried by two methods: freeze-drying or air-drying. The effect of drying method on the properties and structure of the whiskers were studied. Furthermore, the influence of the source of cellulose on the nanoscale structure was investigated. Drying method was observed to slightly influence the thermal stability of cellulose whiskers, whereas the char residue varied significantly depending on the drying process performed. Small- and wide-angle X-ray scattering and solid state nuclear magnetic resonance spectroscopy were used to examine the crystallinity and nanoscale structure of the dried whiskers. It was observed that the crystal structure and crystallinity of cellulose whiskers remained during all treatments, whereas their nanoscale structure was significantly influenced by drying method, neutralization, and source of cellulose. Relationships between thermal behavior and nanoscale structure were reported and discussed.     

Nanofibrillated cellulose/carboxymethyl cellulose composite with improved wet strength

In this paper, nanofibrillated cellulose/carboxymethyl cellulose (CMC) composite films were prepared using tape casting. The obtained transparent films showed shear induced partial alignment of fibrils along the casting direction, resulting in birefringence in cross polarized light. The carboxyl groups of CMC could be further utilized to create ionic crosslinking by treatment with glycidyl trimethyl ammonium chloride (GTMA). The GTMA treated composite films had improved mechanical properties both in wet and dry state. The chemical composition and morphologies of composites were analyzed with X-ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy and wide-angle X-ray scattering.     

Copper and copper oxide nanoparticles in a cellulose support studied using anomalous small-angle X-ray scattering

Microcrystalline cellulose is a porous natural material which can be used both as a support for nanoparticles and as a reducer of metal ions. Cellulose supported nanoparticles can act as catalysts in many reactions. Cu, CuO, and Cu₂O particles were prepared in microcrystalline cellulose by adding a solution of copper salt to the insoluble cellulose matrix and by reducing the copper ions with several reducers. The porous nanocomposites were studied using anomalous small angle X-ray scattering (ASAXS), X-ray absorption spectroscopy, and X-ray diffraction. Reduction of Cu²⁺ with cellulose in ammonium hydrate medium yielded crystalline CuO nanoparticles and the crystallite size was about 6–20 nm irrespective of the copper concentration. The size distribution of the CuO particles was determined with ASAXS measurements and coincided with the crystallite sizes. Using sodium borohydrate or hydrazine sulfate as a reducer both metallic Cu and Cu₂O nanoparticles were obtained and the crystallite size and the oxidation state depended on the amount of reducer.     

Langmuir-Blodgett films of hydrophobins HFBI and HFBII

Hydrophobins are small fungal proteins, which have remarkable surface-chemical properties. They self-assemble at hydrophobic/hydrophilic interfaces and work as adhesive agents and coatings. Sixteen layer Langmuir-Blodgett films of hydrophobins HFBI and HFBII from the fungus Trichoderma reesei were prepared and studied using grazing-incidence X-ray diffraction and reflectivity techniques. Both kind of films contain hexagonally ordered crystallites on the substrate with unit cell parameters of a = b = 54 Å (HFBI) and a = b = 55 Å (HFBII). The structure is similar to the structure of monolayer Langmuir-Blodgett films.     

Polypropylene/organoclay nanocomposites compatibilized with hydroxyl‐functional polypropylenes

The properties of polypropylene composites can be tailored through the use of nanoclay fillers. The effectiveness of a metallocene‐catalyzed hydroxyl‐functional polypropylene in the compatibilization of polypropylene layered nanosilicate composites was studied, and the results were compared with those for a commercial maleic anhydride functionalized polypropylene. Polypropylene/organoclay nanocomposites were prepared by melt blending, and two polypropylene/compatibilizer/organoclay ratios, 90/5/5 and 70/20/10, were characterized. The organomodification of the clay was carried out with octadecylamine and N‐methylundecenylamine. The structure of the layered silicate was studied by transmission electron microscopy, wide‐angle X‐ray scattering, and small‐angle X‐ray scattering. The fracture surfaces of the composites and thus the efficiency of the compatibilizers to penetrate the galleries of the organoclays were characterized by scanning electron microscopy, and the melt viscosity was studied by stress‐controlled rotational rheometry. The nanostructure was observed with both alkyl amines used for intercalation. The fillers facilitated the processability of all the composites, consisting of equal amounts of compatibilizer and organoclay filler and, in some of the composites, containing twice as much compatibilizer as organoclay filler. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1892–1903, 2005     

Cloning of two genes (LAT1,2) encoding specific L: -arabinose transporters of the L: -arabinose fermenting yeast Ambrosiozyma monospora

We identified and characterized two genes, LAT1 and LAT2, which encode specific l-arabinose transporters. The genes were identified in the l-arabinose fermenting yeast Ambrosiozyma monospora. The yeast Saccharomyces cerevisiae had only very low l-arabinose transport activity; however, when LAT1 or LAT2 was expressed, l-arabinose transport was facilitated. When the LAT1 or LAT2 were expressed in an S. cerevisiae mutant where the main hexose transporters were deleted, the l-arabinose transporters could not restore growth on d-glucose, d-fructose, d-mannose or d-galactose. This indicates that these sugars are not transported and suggests that the transporters are specific for l-arabinose.     

Capacity estimates

The relationships between certain Sobolev-Orlicz capacities are worked out. This, in particular, determines their null sets.

     

On fractional Poincaré inequalities

We show that fractional (p, p)-Poincaré inequalities and even fractional Sobolev-Poincaré inequalities hold for bounded John domains, and especially for bounded Lipschitz domains. We also prove sharp fractional (1,p)-Poincaré inequalities for s-John domains.     

ASAXS study of styrene‐grafted sulfonated poly(vinylidene fluoride) membranes

Small‐angle and wide‐angle X‐ray scattering and anomalous small‐angle X‐ray scattering were used to investigate proton‐conducting membranes prepared by radiation‐induced styrene grafting and sulfonation of commercial poly(vinylidene fluoride) (PVDF‐g‐PS) films. The membranes retain the lamellar and highly oriented structure of the original PVDF films even through excessive grafting and sulfonation. The sulfonate groups aggregate in the central part of the amorphous layers, where they form a weakly ordered structure that does not show any preferred orientation. This structure is suggested to be lamellar with alternate metal‐sulfonated hydrate and PVDF‐g‐PS layers. The lamellar period is 15.1 Å. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1734–1748, 2000