Search results for " Scanning"

Semicarbazides as gel forming agents for common solvents and liquid crystals

2006

This paper describes the synthesis of 14 new gelling agents with semicarbazide groups as H-bonding motifs and alkyl- and/or azobenzene side groups. They gel solvents like decaline, 1,2-dichlorobenzene and toluene and liquid crystalline mixtures. X-Ray structure analysis shows that the semicarbazides are connected by H-bonds, each molecule to four neighbours. As a result a ribbon is formed with a core of H-bonded semicarbazide groups and alkyl chains sticking to the side. IR measurements show an unchanged H-bonding motif in large crystals and in the gel fibres, even in LC-mixture. During heating the gel melts (rheology), while the H-bonding motif of the crystal disappears (IR and DSC measure…

Synthesis of new soluble polybenzyls by Friedel-Crafts reactions

1999

Soluble polybenzyls were prepared by a catalytic electrophilic Friedel-Crafts type polycondensation between α,α'-dichloro-p-xylene and substituted (by an alkyl or an alkoxy side-chain) mesitylene. The influence of the length of the side-chain on the solubility of the polymer was examined. The polymers were found to be soluble in common organic solvents. Polymer characterizations were made by 13 C nuclear magnetic resonance spectroscopy (NMR), size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and elemental analysis.

Thermogravimetric and calorimetric studies of water absorbed in polyaniline

1995

Abstract Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to study the behavior of residual water absorbed by an emeraldine base and a salt of chemically synthesized polyaniline (PANI—EB, PANI-ES). The matrix of PANI is shown to contain water molecules participating in both reversible and irreversible absorption. In its turn, the reversibly absorbed water consists of two components. The first component (WD 1 ) amounts to 5–7 wt.% and is removable from PANI-EB in a flow of dry nitrogen at room temperature. The second one (6–8 wt.%) of more strongly bonded water (WD 2 ) can be withdrawn from PANI-EB at temperatures from 70 to 150 °C depending on the measu…

Grafting of Molecularly Imprinted Polymer Films on Silica Supports Containing Surface-Bound Free Radical Initiators

2001

Silica particles containing surface-bound free radical initiators have been used as supports for the grafting of thin films of molecularly imprinted polymers (MIPs). This technique offers a means of fine-tuning the layer thickness for improved kinetic properties or enhanced capacity in chromatographic or sensor applications. Thus prepared MIPs imprinted with l-phenylalanine anilide, have been characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), elemental analysis, fluorescence microscopy, and scanning electron microscopy (SEM), providing evidence concerning the reproducibility in each step and the quantity and quality of the grafted…

New insights for materials science characterisation using different complementary techniques combined with X-ray absorption Spectroscopy

2005

The combination of x-ray absorption spectroscopy (XAS) with UV-Vis and Raman spectroscopies or with Differential Scanning Calorimetry (DSC) has been recently carried out on the D44 beamline of DCI-LURE. The different set-ups used to perform such combinations are described and examples of combined investigations belonging to different field of materials science (coordination chemistry, sol-gel and catalysis) are presented.

Polymers films with indandione derivatives as alternatives to azobenzene polymers for optical patterning

2008

Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific interest and in relevance to the applications. Among the chromophores being used the azobenzenes showed the best performance, but the use of alternative photo-sensitive groups provides better general understanding of the phenomena. A thermodynamic theory and molecular dynamics simulations of photoinduced effects are discussed. In this study we use indandione derivatives, known as promising materials for photonics applications, as an alternative to the azobenzenes. We consider their photoreactions when incorporated into a polymer film. One of interesting features is the spectral dependence of the…

Influence of alginate emulsion-based films structure on its barrier properties and on the protection of microencapsulated aroma compound

2009

In recent years the use of natural polymers coming from renewable sources has greatly increased due to the over-solid packaging waste and dwindling petroleum reserves. Biopolymer films, which contain both lipid and polysaccharide ingredients to form complex packaging enable us to obtain edible films with good mechanical and water barrier properties as emulsified alginate edible films. Moreover, these can be considered to encapsulate active molecules as flavours. The aim of this work is to better understand the influence of the composition and the structure of the film matrix on its barrier properties and thus on its capacity to protect encapsulated active substances. Granulometry, Different…

Polyethylene composites filled with n‐alkyl‐functionalized siloxane‐silsesquioxane resins and sol‐gel silicas

2019

High‐density polyethylene (HDPE) composites filled with silicon‐based fillers were prepared by melt blending. The use of non‐functionalized and n‐octyl‐functionalized siloxane‐silsesquioxane resins and the sol‐gel silicas as fillers allowed us to evaluate the influence of functionalization of the fillers on the properties of the composites. The melting and crystallization temperatures of the composites were found to be only slightly affected by the addition of the silicon‐based fillers. In turn, the crystallization degree values were increased, in particular for the materials containing non‐functionalized fillers. The free‐volume properties of the composites did not change significantly in …

1992

The synthesis and the results of the structural study of two copolysiloxanes with laterally fixed trinitrofluorenone (TNF) units is reported. The two copolysiloxanes having 2,4 (1a) and 5,3 (1b) dimethylsiloxane comonomer units per TNF side group differ significantly in their phase behaviour as evident from optical microscopy, differential scanning calorimetry and X-ray scattering: 1b shows a nematic mesophase whereas 1a is an amorphous material. The different phase behaviour is discussed in terms of microphase separation between the siloxane backbone and TNF side groups.

Temperature-Induced Structural Transitions in the Gallium-Based MIL-53 Metal–Organic Framework

2013

We report a structural and thermodynamic investigation of the phase behavior of Ga(OH,F)-MIL-53, a gallium-based metal–organic framework (MOF) having the MIL-53 topology containing 0.7 wt % fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, and heat capacity measurements allowed us to establish that Ga(OH,F)-MIL-53 under vacuum (i.e., the empty material) exhibits two stable phases: a nonporo…