Search results for "Solid"
showing 10 items of 3575 documents
Solid State Structures of Amide-Substituted 8-Hydroxyquinoline Derivatives
2000
Abstract The amide substituted 8-hydroxyquinoline derivatives 3 and 4 form, in the solid state, hydrogen bonded polymers. Polymeric 3 adopts a helical conformation while 4 forms a double-stranded ladder-type structure.
Synthesis of high surface area perovskite catalysts by non-conventional routes
1997
Abstract The use of rare earth-containing perovskite oxides as total oxidation catalysts faces to the difficulty of obtaining high surface area materials and the need of calcination at high temperatures for its synthesis. In this work, perovskite NdCoO3 catalysts with relatively high surface areas were synthesized at soft calcination conditions by two non-conventional routes: heteronuclear organic complexes and amorphous precursors obtained by freeze-drying of nitrates solutions. Depending on the method used, different degrees of homogeneity in the bulk distribution of the component cations, oxygen non-stoichiometry as well as surface Co/Nd atomic ratios are obtained. In this way, the synth…
The water association band as a marker of hydrogen bonds in trehalose amorphous matrices
2017
The relevant role played by residual water in modulating the dynamics and structure of a protein, a matrix and their coupling has been thoroughly studied in bioprotective amorphous saccharide matrices via experiments and simulations. In order to better characterize this residual water and the hydrogen bond structures in which it is involved, in this work infrared spectroscopy experiments are conducted on trehalose-water systems. The properties of water are inferred from the study of a peculiar infrared band, the water association band, which we exploited as a marker of the hydrogen bonds in which water is involved. Our aim was the identification of populations of water molecules, which give…
Growing range of correlated motion in a polymer melt on cooling towards the glass transition
1999
Many liquids cooled to low temperatures form glasses (amorphous solids) instead of crystals. As the glass transition is approached, molecules become localized and relaxation times increase by many orders of magnitude1. Many features of this ‘slowing down’ are reasonably well described2 by the mode-coupling theory of supercooled liquids3. The ideal form of this theory predicts a dynamical critical temperature T c at which the molecules become permanently trapped in the ‘cage’ formed by their neighbours, and vitrification occurs. Although there is no sharp transition, because molecules do eventually escape their cage, its signature can still be observed in real and simulated liquids. Unlike c…
Synthesis of glycosylated β3-homo-threonine conjugates for mucin-like glycopeptide antigen analogues
2010
Glycopeptides from the mucin family decorated with tumour-associated carbohydrate antigens (TACA) have proven to be important target structures for the development of molecularly defined anti-cancer vaccines. The strategic incorporation of β-amino acid building blocks into such mucin-type sequences offers the potential to create pseudo-glycopeptide antigens with improved bioavailability for tumour immunotherapy. Towards this end, TN and TF antigen conjugates O-glycosidically linked to Fmoc-β3-homo-threonine were prepared in good yield via Arndt–Eistert homologation of the corresponding glycosyl α-amino acid derivative. By incorporation of TN-Fmoc-β3hThr conjugate into the 20 amino acid tand…
Photoinduced mass transport in soft materials
2011
The surface relief grating formation in amorphous As2S3 and azo-benzene polymer films strongly depends on the polarization state of recording beams. The surface relief grating formation efficiency of s-s and p-p recording beam combination can be essentially enhanced by additional illumination with orthogonal polarization. It is shown that the direction of mass transport on the film surface is determined by the direction of light electric vector.
The viscoelastic behavior of nylon 6/lithium halides mixtures
1980
Stress-relaxation experiments in the limit of small deformations have been carried out in a wide range of temperatures for pure nylon 6 and its mixtures with LiBr and/or LiCl. Master curves have been constructed, by allowing horizontal shifts only, showing the shape typical for semicrystalline polymers in the case of pure nylon and that of essentially amorphous polymers in the case of salted samples. The glass transition temperatures determined from the plot logaT− 1/T is increased when in the presence of salts. All such effects are considered to reflect the binding action of Li+ and Br− ions.
Light emitting and electrical properties of pure amorphous thin films of organic compounds containing 2-tert-butyl-6-methyl-4H-pyran-4-ylidene
2013
Abstract Low molecular weight organic compounds which make thin films from organic solutions would be a great benefit in future organic light emitting systems. Two most important advantages should be mentioned. First – repeatability of synthesis of small molecules is better than of polymers. Second – wet casting methods can be applied. In this paper we present optical and opto-electrical properties of three glassy forming compounds containing 2-tert-butyl-6-methyl-4H-pyran-4-ylidene fragment as a backbone. They have the same N,N-dialkylamino electron donating group with attached bulky trityloxyethyl groups. The difference between these compounds is in an electron acceptor group. One has ind…
Nematic elastomers: From a microscopic model to macroscopic elasticity theory
2008
A Landau theory is constructed for the gelation transition in cross-linked polymer systems possessing spontaneous nematic ordering, based on symmetry principles and the concept of an order parameter for the amorphous solid state. This theory is substantiated with help of a simple microscopic model of cross-linked dimers. Minimization of the Landau free energy in the presence of nematic order yields the neoclassical theory of the elasticity of nematic elastomers and, in the isotropic limit, the classical theory of isotropic elasticity. These phenomenological theories of elasticity are thereby derived from a microscopic model, and it is furthermore demonstrated that they are universal mean-fi…
Halloysite Nanotubes for Cleaning, Consolidation and Protection
2017
Herein, we report our recent research concerning the development of halloysite based protocols for cleaning, consolidation and protection purposes. Surface modification of halloysite cavity by anionic surfactants was explored to fabricate inorganic micelles able to solubilize hydrophobic contaminants. Hybrid dispersions based on halloysite and ecocompatible polymers were tested as consolidants for paper and waterlogged archaeological woods. Encapsulation of deacidifying and flame retardant agents within the halloysite lumen was conducted with aim to obtain nanofiller with a long-term protection ability. The results prove the suitability and versatility of halloysite nanotubes, which are per…