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Flax fibers composed mainly of cellulose were subjected to heterogeneous valerylation reaction. The progress of the chemical modification was assessed by transmission FTIR. The heterogeneous esterification reaction followed first-order kinetics, and a plateau was reached already after 30 min. The intensity of the FTIR hydroxyl absorption band (nu = 3400 cm(-1)) did not appreciably decrease during the acylation reaction, showing that only a small fraction of the fiber hydroxyls was involved in the reaction. The degree of valerate substitution (DS) at the fiber surface (50 A thick layer) was evaluated by means of ESCA. Surface valerylation increased with reaction time and leveled off at DS around 1 after 30 min, in agreement with the FTIR data. The chemically modified fibers maintain the Cellulose I crystal structure and the original crystallinity degree up to the longest reaction time investigated (180 min). Dynamic contact angle measurements showed that surface hydrophobicity as indicated by advancing contact angle rapidly increased upon valerylation reaching a plateau after about 10 min. Chemical modification does not appreciably alter fiber thermal stability (by TGA) and morphology (by SEM).
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PMID:Heterogeneous acylation of flax fibers. Reaction kinetics and surface properties. 1274 4

The chemical stability of fluoronanotubes in selected solid inorganic matrixes has been studied by initially mixing and mechanically grinding the components and subsequently heating them at temperatures ranging from 35 to 600 degrees C. The inorganic compounds selected for matrixes included halides (KBr, KI, Lil, LiBr, LiCl, NaCl, Znl2), oxides (Li2O, Fe2O3, PbO, MnO), lithium peroxide (Li2O2), potassium superoxide (KO2), sulfides (Li2S and ZnS), zinc selenide (ZnSe), lithium nitride (Li3N), and aluminum phosphide (AIP). Solid products, resulting from the proceeding chemical reactions, were analyzed by X-ray diffraction, Raman spectroscopy, and SEM/EDX elemental analysis. Gaseous and volatile products were identified with the help of the TGA/MS technique. Experimental data presented in this paper provide clear evidence that fluoronanotubes are not chemically inert toward the solid matrixes studied and exhibit significant oxidative properties in the redox reactions occurring under various temperatures, depending on the nature of the inorganic compound.
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PMID:Oxidative properties and chemical stability of fluoronanotubes in matrixes of binary inorganic compounds. 1290 34

Chiral porous zirconium phosphonates containing Ru-BINAP-DPEN moieties were synthesized via a molecular building-block approach, and characterized by a variety of techniques including TGA, adsorption isotherms, XRD, SEM, IR, and microanalysis. These hybrid solids were used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with remarkably high ee values of up to 99.2%. These solid catalysts can also be easily recycled and reused for eight times without the loss of activity and enantioselectivity. Ready tunability of such a molecular building-block approach will allow the optimization of these hybrid materials and promise to lead to other practically useful heterogeneous asymmetric catalysts.
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PMID:Chiral porous hybrid solids for practical heterogeneous asymmetric hydrogenation of aromatic ketones. 1312 39

The first chainlike germanate, [Ge(7)O(13)(OH)(2)F(3)](3)(-).Cl(-).2[Ni(dien)(2)](2+), has been solvothermally synthesized by using Ni(dien)(2)(2+) cations as the template and characterized by IR, SEM, TGA, powder X-ray diffraction (PXRD), energy-dispersive X-ray analysis (EDXA), elemental analysis, and single-crystal X-ray diffraction, respectively. This compound crystallized in the monoclinic space group P2/nwith a = 8.8904(2) A, b = 17.4374(3) A, c = 13.2110(3) A, beta = 101.352(1) degrees, V = 2007.97(7) A(3), and Z = 2. Interestingly, the structure contains two types of chiral mer-[Ni(dien)(2)](2+) cations and two types of chiral chains, one left-handed and the other right-handed, which lead to a racemic compound. The orderly separation of achiral s-fac-[Ni(dien)(2)](2+) and chiral mer-[Ni(dien)(2)](2+) isomers was found in the structure. The structure is stabilized by N-H.O(F, Cl) hydrogen bonds.
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PMID:[Ge(7)O(13)(OH)(2)F(3)](3)(-).Cl(-).2[Ni(dien)(2)](2+): the first chainlike germanate templated by a transition metal complex. 1455 7

This study deals with the generation and characterization of various solid-state forms of celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor. The drug was subjected to polymorphic screen using different solvents to explore the possibility of existence of different solid forms. N,N-Dimethyl acetamide (DMA) and N,N-dimethyl formamide (DMF) yielded solvates in 1:1 stoichiometric ratio. Quench cooling of the melt resulted in amorphous form of the drug. All these solid-state forms were characterized by thermoanalytical (DSC, TGA, HSM), crystallographic (XRD), microscopic (polarized, SEM), spectroscopic (FTIR), and elemental analysis techniques. Solubility and van't Hoff studies were carried out for their thermodynamic interpretation. Influence of morphology of different solid-state forms on flow behavior was also investigated. Molecular modeling studies were used to elucidate the interaction between solute and solvent molecules in the solvate.
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PMID:Characterization of solid-state forms of celecoxib. 1459 96

The in situ ATRP (atom transfer radical polymerization) "grafting from" approach was successfully applied to graft poly(methyl methacrylate) (PMMA) onto the convex surfaces of multiwalled carbon nanotubes (MWNT). The thickness of the coated polymer layers can be conveniently controlled by the feed ratio of MMA to preliminarily functionalized MWNT (MWNT-Br). The resulting MWNT-based polymer brushes were characterized and confirmed with FTIR, 1H NMR, SEM, TEM, and TGA. Moreover, the approach has been extended to the copolymerization system, affording novel hybrid core-shell nanoobjects with MWNT as the core and amphiphilic poly(methyl methacrylate)-block-poly(hydroxyethyl methacrylate) (PMMA-b-PHEMA) as the shell. The approach presented here may open an avenue for exploring and preparing novel carbon nanotubes-based nanomaterials and molecular devices with tailor-made structure, architecture, and properties.
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PMID:Controlled functionalization of multiwalled carbon nanotubes by in situ atom transfer radical polymerization. 1471 7

Solid-state properties of piroxicam benzoate, an ester prodrug of piroxicam, were investigated. Samples were prepared by recrystallization from various organic solvents (toluene, ethanol, methanol, ethyl acetate and acetone). Recrystallized samples were characterized by means of FTIR, DSC, TGA, SEM and XRPD. DSC, TGA and XRPD methods confirmed that piroxicam benzoate crystallized in two pseudopolymorphic forms, A and B. Pseudopolymorphic form A was obtained by recrystallization from ethanol and methanol by slow cooling at room temperature and by rapid cooling in an ice-cold bath, and also from toluene by rapid cooling in an ice-cold bath. Pseudopolymorphic form B was obtained by recrystallization from toluene by slow cooling at room temperature.
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PMID:Solid-state investigation of piroxicam benzoate. 1476 40

The new layered germanate structure Na4Ge16O28(OH)12 has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, FTIR, and SEM. The crystal lattice parameters are a = 7.3216(6) A, b = 14.3986(9) A, c = 7.7437(6) A, alpha = 90.0 degrees, beta = 100.179(7) degrees, gamma = 90.0 degrees, and V = 803.5(1) A3. The space group is C2/m with Z = 1. The germanium oxide sheets are connected non-covalently via electrostatic interactions with the sodium cations and H-bridging. At temperatures above 400 degrees C, the structure starts decomposing into sodium enneagermanate (Na4Ge9O20), germanium dioxide, and water as determined by powder X-ray diffraction, TGA, DTA, DSC, and GCMS.
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PMID:Synthesis, structural characterization, and thermal stability of a new layered germanate structure, Na4Ge16O28(OH)12. 1510 76

Ordered macroporous organosilica materials with uniform pore size in the range of 0.2-1.35 [micro sign]m have been fabricated by using self-assembled colloidal crystals as templates, and characterized with SEM, TGA, FTIR, MAS NMR, and optical reflectance spectrometry.
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PMID:Synthesis, characterization and optical properties of ordered macroporous organosilicas. 1517 72

The first noncentrosymmetric potassium templated borogermanate, K(2)[Ge(B(4)O(9))].2H(2)O, has been solvothermally synthesized and characterized by IR, SEM, powder X-ray diffraction (PXRD), TGA, energy dispersive spectroscopy (EDS), single crystal X-ray diffraction, and second harmonic generation (SHG) activity, respectively. This compound crystallized in the monoclinic space group Cc with a = 6.793(1) A, b = 12.0699(3) A, c = 11.895(3) A, beta = 91.156(4) degrees, V = 975.1(4) A(3), and Z = 4. Interestingly, the structure possesses a unique 3D alternating linkage mode of B(4)O(9) clusters and GeO(4) units and contains two pairs of interweaving double helical channels with a 10-membered ring. In one, the right- and left-handed helices couple each other, and in the other, the left- and right-handed helices couple together. The compound exhibits distinct nonlinear optical (NLO) properties because it lacks a symmetric center. Furthermore, the framework of the title compound not only displays high thermal stability but also can be recoverable to a large degree during a dehydration-hydration cycle.
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PMID:K2[Ge(B4O9)].2H2O: a unique 3D alternating linkage mode of a B4O9 cluster and GeO4 unit in borogermanate with two pairs of interweaving double helical channels. 1544 58


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