Aldo D'Alessio

FT-IR investigation of the structural changes of Sulcis and South Africa coals under progressive heating in vacuum

Two samples of coals coming from South Africa and Sulcis (Sardinia, Italy) were subjected to progressive heating up to 800°C in vacuum. The infrared (IR) spectra of the residuals obtained at 100°C intervals from room temperature to 800°C show spectral changes ascribed to transformations at the level of the organic and inorganic components. Comparing these results with those previously obtained by heating the same coals in the presence of air and examining their pyridinic extracts, it appears that the Sulcis coal with respect to the other coals contains a lower amount of clay-minerals. Furthermore, the IR analysis shows that this coal is nearer to being a lignite than a hard-coal.

LOW-TEMPERATURE AIR OXIDATION OF COAL AND ITS PYRIDINE EXTRACTION PRODUCTS - FOURIER-TRANSFORM INFRARED STUDIES

Abstract Fourier transform infrared spectroscopy has been used to study the evolution of the structure of a bituminous coal and its pyridine extraction products during oxidation. Different methods of analysis of the spectra have been used, such as curve-resolving routines, coupled to second derivative methods and area integration. The pyridine extract has been found to maintain the characteristic absorption bands of the original coal and to present marked susceptibility towards oxidation, to a greater extent than its parent coal. The analysis of the coal, extract and residue spectra and their comparison as oxidation proceeds, give an insight into the complex phenomena occurring. Pyridine extract spectra present a better separation of contributions of the bands involved, by the low temperature oxidation of low rank coals, particularly in the zones 3500-2800 and 1800-1500 cm −1 .

FTIR-microspectroscopy and DSC studies of poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVDF) samples, obtained by casting from tetrahydrofuran solutions and submitted to various thermal treatments, have been examined by Fourier transform-infrared microspectroscopy (FTIR-M) and differential scanning calorimetry (DSC). This kind of analysis allowed us to examine microdomains of samples with different morphological characteristics and to obtain an indication of the polymorphism of PVDF. In some cases the simultaneous presence of two or three forms has been evidenced thanks to the comparison of FTIR-M spectra and DSC traces. Vibrational spectra of single crystalline forms can be recorded by FTIR-M on phase homogeneous microdomains.

Novel Highly Active Niobium Catalysts for Ring Opening Metathesis Polymerization of Norbornene

Ring-opening metathesis polymerization (ROMP) of norbornene catalyzed by niobium(V) N,N-dialkylcarbamates Nb(O(2) CNR(2) )(5) , R = Et (1), Me (2) was studied in the presence of methylaluminoxane (MAO) as a cocatalyst. These novel catalytic systems resulted very active in chlorobenzene: 1 in the presence of methylaluminoxane catalyzes the ROMP of norbornene with the highest activity (29 000 kg of polymer/mol of catalyst × hour) never reported up to now for niobium catalysts. The high productivity appears particularly attractive considering that these precursors are rather cheap and easy to synthesize and to handle. Polynorbornenes were characterized by FT-IR and NMR spectroscopies and by DSC calorimetry. A new FT-IR method for the swift determination of the cis/trans content of the polymer is presented.

Characterization of acrylic resins and fluoroelastomer blends as potential materials in stone protection

Films of blends of Paraloid® B72 (copolymer of ethyl methacrylate and methyl acrylate) and Tecnoflon NM® (copolymer of vinylidene fluoride and hexafluoropropene) with different compositions were investigated by means of FT-IR spectroscopy and FT-IR microspectroscopy before and after UV and thermal treatments. Preliminary results of DSC measurements are also reported. Paraloid B72 has been extensively applied as a protective agent for stone since the 1950s. More recently considerable research has also been carried out on the application of fluorinated polymers in the field of stone conservation, eg the fluoroelastomer Tecnoflon®. A high content of Tecnoflon with respect to Paraloid increases the stability of the blends when they are submitted to UV radiation and thermal treatments. A THF solution of a blend of this kind was successfully applied to a marble surface of the Saint Maria Cathedral in Lucca, Tuscany, Italy. The changes in the properties of such mixtures with different compositions can offer new possibilities in developing suitable protective materials. © 2000 Society of Chemical Industry

QUALITATIVE AND QUANTITATIVE ANALYSIS OF THE SECONDARY STRUCTURE OF CYTOCHROME C LANGMUIR-BLODGETT FILMS

A qualitative and quantitative analysis of the conformation of Langmuir-Blodgett (LB) dried films of cytochrome C on silicon wafers was performed by Fourier transform ir (FTIR) spectroscopy. A deconvolution procedure was applied to the amide I band analysis, in order to determine the percentage of the different secondary structures. Qualitative analysis was performed by examining difference spectra. Films obtained by spreading protein solutions at pH 7.4 and 1, dried at 25 and 100 degrees C, on silicon wafers were also examined in order to detect spectral components associated with denatured protein domains, and to compare them with cytochrome C LB films. FTIR spectroscopy showed that the following important changes characterise LB film spectra: (a) the alpha-helix component is higher (its percentage is 57 and 54%) than the one estimated in dried film obtained by spreading the solutions at pH 7.4 on a silicon substrate (43%), (b) there is an increase in the intensity of bands attributed to protonated carboxy group bands, involved and not involved in the formation of hydrogen bonds, and a decrease in those attributed to deprotonated carboxy groups, (c) the intensity of several bands attributed to aromatic amino acids and aliphatic chains increases, and (d) bands due to O-H stretching vibrations of crystallization water are present. These conformational changes could be induced by protein-protein interaction caused by the close packing of molecules that occurs during LB film formation; it cannot be excluded that they may be accompanied by partial changes in the tertiary structure of the protein. A preferential orientation of protein molecules in LB films is also a possibility.

Influence of molecular weight on the crystallization of poly(vinylidene fluoride)

AbstractFive samples of Poly (vinylidene fluoride) with a molecular weight from 45,000 to 260,000 were analyzed by means of FT-IR spectroscopy in order to study the influence of molecular weight

FT-IR Investigation of the Structural Changes of Sulcis and South Africa Coals under Progressive Heating in Vacuum: Correlation with Volatile Matter

\left( {\bar Mv} \right)