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- Organització i estructura
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Afegeix-ho a l'agenda (iCal)
Conferenciant: Dr. Diana Ciolacu “Petru Poni”, Institute of Macromolecular Chemistry, Iasi, Romania
Cellulose is a very important and fascinating biopolymer and an almost inexhaustible and renewable raw material. The degree of knowledge on the structure of cellulose has evolved along with the progress made in the field of polymers, cellulose being the first macromolecular compound that was extensively studied during implementation and development of the concept of a macromolecule. Even though cellulose was isolated over 180 years ago, the study of this natural polymer has still remained of interest to scientists.
The presentation will be focused on the polymorphism of cellulose which still intrigue us through the non-elucidated aspects regarding both the obtaining and the structural organization of the allomorphic forms of cellulose. The interconversions between the allomorphic structures can be performed by the action of chemical reagents or thermal treatments. The use of the X-rays diffraction method of investigation permitted us to observe that each cellulose allomorph presents a specific roentgenogram. The allomorphs of cellulose are different from the supramolecular structure point of view, such as the dimensions of monoclinic unit cell, densities of intra- and intermolecular bonds, polarity, and the packing degrees of macromolecular chains.
The accessibility is a structural parameter that depends on the nature of the interactions that take place between a reactant and the cellulosic substrate. These interactions are influenced by the availability of the inner surface, by the supramolecular organization and by the fibrillar architecture. The assessment of the accessibility of cellulosic materials will be explained through the water vapor sorption method and the enzymatic hydrolysis process.