<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Lopes, M H</style></author><author><style face="normal" font="default" size="100%">Sarychev, A</style></author><author><style face="normal" font="default" size="100%">Neto, C P</style></author><author><style face="normal" font="default" size="100%">Gil, A M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Spectral editing of 13C cp/MAS NMR spectra of complex systems: application to the structural characterisation of cork cell walls.</style></title><secondary-title><style face="normal" font="default" size="100%">Solid state nuclear magnetic resonance</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">13CCPrMAS NMR</style></keyword><keyword><style  face="normal" font="default" size="100%">Cork</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymer</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus suber L.</style></keyword><keyword><style  face="normal" font="default" size="100%">Relaxation</style></keyword><keyword><style  face="normal" font="default" size="100%">Spectral editing</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><volume><style face="normal" font="default" size="100%">16</style></volume><pages><style face="normal" font="default" size="100%">109-121</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A mathematical method of obtaining 13C CP/MAS subspectra of single components of a complex system is presented and applied to three- and four-component systems. The method is based on previously reported work that exploits different proton relaxation properties for different domains of an heterogeneous system. However, unlike the original method that obtained subspectra through a trial-and-error approach, the method here presented solves the problem mathematically, thus avoiding the time-consuming and non-rigorous trial-and-error step. The method is applied to mixtures of three and four polymers and to a more complex system: cork cell walls. As expected, as the number of components increases, the sharing of relaxation properties between different components is increasingly probable, either due to incidental coincidence of relaxation times or to specific interactions and intimate mixing of compounds. While this hinders the calculation of the subspectra of single chemical components, it may provide useful information about inter-component interactions. This possibility was demonstrated by the application of this method to cork cell walls. Both three-component and four-component approaches showed that three domains exist in cork cell walls: carbohydrate/lignin matrix, mobile suberin close to (probably bonded to) lignin groups (about 42% w/w) and hindered suberin close to (probably bonded to) carbohydrate-OCH2O groups (about 4% w/w).</style></abstract><accession-num><style face="normal" font="default" size="100%">10868562</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cordeiro, N</style></author><author><style face="normal" font="default" size="100%">Belgacem, M N</style></author><author><style face="normal" font="default" size="100%">Gandini, A</style></author><author><style face="normal" font="default" size="100%">Neto, C P</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Urethanes and polyurethanes from suberin 2: synthesis and characterization</style></title><secondary-title><style face="normal" font="default" size="100%">INDUSTRIAL CROPS AND PRODUCTS</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork</style></keyword><keyword><style  face="normal" font="default" size="100%">glass transition</style></keyword><keyword><style  face="normal" font="default" size="100%">polyurethanes</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus suber L.</style></keyword><keyword><style  face="normal" font="default" size="100%">suberin</style></keyword><keyword><style  face="normal" font="default" size="100%">thermal properties</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><publisher><style face="normal" font="default" size="100%">ELSEVIER SCIENCE BV</style></publisher><pub-location><style face="normal" font="default" size="100%">PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS</style></pub-location><volume><style face="normal" font="default" size="100%">10</style></volume><pages><style face="normal" font="default" size="100%">1-10</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Polyurethanes based on suberin from cork of Quercus suber L. and conventional isocyanate monomers were prepared and fully characterized in terms of both structure (FTIR and H-1 NMR spectroscopy) and thermal properties (differential scanning calorimetry and thermogravimetric analysis). Two fractions were systematically isolated, namely (i) methylene-chloride soluble products, which corresponded to linear and branched macromolecules and (ii) methylene-chloride insoluble products, representing the crosslinked material. The structures of these polymers were regular and no appreciable side reactions were detected. DSC analyses provided information about the glass transition temperature of both fractions and this parameter was correlated with the stiffness of the isocyanate used. The TGA of these polyurethanes showed that they started to degrade at about 175 degrees C and that the residue at 400 degrees C was around 50%. The highest amounts of insoluble fractions, as well as the highest T-g,s, were reached when an initial \{[\}NCO]/\{[\}OH] of unity was used. (C) 1999 Elsevier Science B.V. All rights reserved.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cordeiro, N</style></author><author><style face="normal" font="default" size="100%">Belgacem, N M</style></author><author><style face="normal" font="default" size="100%">Gandini, A</style></author><author><style face="normal" font="default" size="100%">Neto, C P</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Cork suberin as a new source of chemicals: 2. Crystallinity, thermal and rheological properties</style></title><secondary-title><style face="normal" font="default" size="100%">Bioresource technology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Alkaline methanolysis</style></keyword><keyword><style  face="normal" font="default" size="100%">cork of Quercus suber L.</style></keyword><keyword><style  face="normal" font="default" size="100%">crystallinity</style></keyword><keyword><style  face="normal" font="default" size="100%">Density</style></keyword><keyword><style  face="normal" font="default" size="100%">rheological properties</style></keyword><keyword><style  face="normal" font="default" size="100%">suberin</style></keyword><keyword><style  face="normal" font="default" size="100%">thermal characterization</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><volume><style face="normal" font="default" size="100%">63</style></volume><pages><style face="normal" font="default" size="100%">153-158</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Suberin samples, obtained by alkaline methanolysis from cork (Quercus suber L.), were submitted to various physical characterizations; DSC, TGA, optical microscopy, density and rheological properties. A sub- stantial proportion of these oligomers possessed a microcrystalline character with a melting range between 0 and 50°C. The amorphous part was liquid at room temperature and did not display a detectable glass transition upon cooling because of its wide molecular weight distribution. The viscous behaviour of suberin at room temperature was both plastic and thixotropic because of the structuring role of the micro- crystals</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>3</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cordeiro, N</style></author><author><style face="normal" font="default" size="100%">Belgacem, M N</style></author><author><style face="normal" font="default" size="100%">Gandini, A</style></author><author><style face="normal" font="default" size="100%">Neto, C P</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Kopetz, H and Weber, T and Palz, W and Chartier, P and Ferrero, G L</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Suberin-based polyurethanes: Synthesis, characterization and kinetics of their formation</style></title><secondary-title><style face="normal" font="default" size="100%">BIOMASS FOR ENERGY AND INDUSTRY</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">aliphatic isocyanates</style></keyword><keyword><style  face="normal" font="default" size="100%">aromatic isocyanates</style></keyword><keyword><style  face="normal" font="default" size="100%">kinetic study</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus suber L.</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><publisher><style face="normal" font="default" size="100%">CENTRALES AGRAR ROHSTOFF MKT &amp; ENTWICKLUNG NETZWERK</style></publisher><pub-location><style face="normal" font="default" size="100%">TECHNOL PK 13, D-97222 RIMPAR, GERMANY</style></pub-location><pages><style face="normal" font="default" size="100%">386-389</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The synthesis and characterization of novel family of polyurethanes prepared by the polycondensation of suberin from Quercus suber L. with aliphatic and aromatic isocyanates are reported. A preliminary kinetic study, conducted with the aim of establishing the reactivity of suberin with different mono-, di- and polyisocyanates, showed that the kinetics of these condensations followed the classical second-order behaviour up to conversion of about 90%. The reactivity of different isocyanates followed patterns that could be readily rationalized in terms of steric hindrance and electronic factors, associated with each specific structure. The investigation was then extended to the synthesis of the new polymers which were characterized by FTIR and NMR spectroscopy and DSC. These suberin-based polyurethanes were a mixture of linear, branched and crosslinked structures. The proportion of the latter (insoluble fraction) being the highest for thr syntheses carried out in stoichiometric conditions, viz. \{[\}NCO](o) = \{[\}OH](o). The Tg of these materials depended of the diisocyanates used and correlated with their structural stiffness.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Neto, C P</style></author><author><style face="normal" font="default" size="100%">Cordeiro, N</style></author><author><style face="normal" font="default" size="100%">Seca, A</style></author><author><style face="normal" font="default" size="100%">Domingues, F</style></author><author><style face="normal" font="default" size="100%">Gandini, A</style></author><author><style face="normal" font="default" size="100%">Robert, D</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Isolation and characterization of a lignin-like polymer of the cork of Quercus suber L.</style></title><secondary-title><style face="normal" font="default" size="100%">HOLZFORSCHUNG</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork</style></keyword><keyword><style  face="normal" font="default" size="100%">lignin-like polymer</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus Suber L</style></keyword><keyword><style  face="normal" font="default" size="100%">suberin</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><publisher><style face="normal" font="default" size="100%">WALTER DE GRUYTER &amp; CO</style></publisher><pub-location><style face="normal" font="default" size="100%">GENTHINER STRASSE 13, D-10785 BERLIN, GERMANY</style></pub-location><volume><style face="normal" font="default" size="100%">50</style></volume><pages><style face="normal" font="default" size="100%">563-568</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A lignin-like polymer was successfully extracted from the cork of Quercus suber L. using an organosolv-based technique. This material was characterized by elemental analysis, functional group analysis, nitrobenzene oxidation followed by HPLC analysis of the oxidation products, FTIR and liquid C-13 NMR. The evidence thus obtained indicated that the extracted material was composed mainly of a lignin-like polymer covalently bound to residual aliphatic structures which are not present in common lignins and which have been assigned to suberin. The latter is likely to be attached to the oxygenated side chains of the phenolic polymer but bonding through the aromatic ring can also be envisaged. No residual carbohydrates were detected. The phenolic polymer, composed mainly of guaiacyl-type units and small amounts of syringyl-type units, had a low methoxy content and a high degree of condensation. This polymer showed the presence of a fraction containing C6Cn units with n &lt; 3 or even n &lt; 2.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cordeiro, N</style></author><author><style face="normal" font="default" size="100%">Neto, C P</style></author><author><style face="normal" font="default" size="100%">Gandini, A</style></author><author><style face="normal" font="default" size="100%">Naceur Belgacem, M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Characterization of the cork surface by inverse gas chromatography</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of colloid and interface science</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cork</style></keyword><keyword><style  face="normal" font="default" size="100%">Inverse Gas Chromatography (IGC)</style></keyword><keyword><style  face="normal" font="default" size="100%">surface properties (PG)</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">174</style></volume><pages><style face="normal" font="default" size="100%">246-249</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Inverse gas chromatography (IGC) at infinite dilution has been used to study the surface properties of cork from Quercus suber. The dispersive component of its surface energy was determined at different temperatures using n-alkanes as probes, and a GDS value of 38+-1mJ.m-2 at 40ºC was obtained. The surface acid (A)/base(B) properties were also evaluated by using polar probes and the results indicate that cork has an amphoteric character, with a KA/KB=1.1. The advantages of IGC, compared with the technique of contact angle measurements in the characterization of the cork surface, are discussed</style></abstract></record></records></xml>