Synthetic characterization and Structural Properties of Nanocellulose from Moringa oleifera seeds

In this research, nanocellulose is isolated from Moringa oleifera seed using acid hydrolysis and the structural properties were determined. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used for the characterization of the isolated nanocellulose. The most noticeable peak is observed at and the value of the crystallinity index () from the XRD pattern is 63.1%. The calculated values of hydrogen bond intensity (HBI), lateral order index (LOI) and total crystalline index (TCI) are 0.93, 1.17and 0.94 respectively exhibited high degree of crystallinity and well arranged cellulose crystal structure. The isolated nanocellulose has an average length and diameter of 14.3 and 36.33 respectively. Furthermore, the FTIR peaks revealed the presence of C-H bending, C-O stretching and O-H stretching functional groups.

On cellulose spatial organization and interactions as unraveled by diffraction and spectroscopic methods throughout the 20th century

This contribution attempts to describe the path towards determination of cellulose crystal structure down to atomic coordinates, towards the determination of its molecular conformation, as well as towards the details of the intricate pattern of hydrogen bonds and their dynamics. This path started at the beginning of the 20th century with X-ray diffraction, continued with electron diffraction, infrared and Raman spectroscopy, and significant knowledge was gained by methods of NMR spectroscopy. Towards the end of the 20th century and at the beginning of the 21st century, X-ray diffraction in conjunction with neutron diffraction provided the position of hydrogens, which led to detailed description of the geometry of hydrogen bonding network in cellulose. Quantum chemical and molecular dynamics calculations, polarized infrared spectroscopy and sum frequency generation vibrational spectroscopy were used to identify the origins of the vibrational modes in cellulose and to describe their extensive coupling mediated by hydrogen bonds. The role of amphiphilic character of cellulose macromolecule (and consequent hydrophobic interactions) in cellulose properties and behavior has been gaining more recognition in the 21st century.

Interaction Effects between Cellulose and Water in Nanocrystalline and Amorphous Regions: A Novel Approach Using Molecular Modeling

The hydrophilic/hydrophobic nature of cellulose is based on its structural anisotropy. Cellulose chains are arranged in a parallel manner and are organized in sheets stabilized by interchain OH–O hydrogen bonds, whereas the stacking of sheets is stabilized by both van der Waals (vdW) dispersion forces and weak CH–O hydrogen bonds. Cellulose has a strong affinity to itself and materials containing hydroxyls, especially water. Based on the preponderance of hydroxyl functional groups, cellulose polymer is very reactive with water. Water molecular smallness promotes the reaction with the cellulose chains and immediately formed hydrogen bonds. Besides that, vdW dispersion forces play an important role between these two reactive entities. They stabilize the cellulose structure according to the considerable cohesive energy in the cellulose network. Hydrogen bonding, electrostatic interactions, and vdW dispersion forces play an important role in determining the cellulose crystal structure during the cellulose-water interactions. As a result of these interactions, the volume of cellulose undergoes a meaningful change expressed not only by an exponential growth in amorphous regions, but also by an expansion in nanocrystalline regions. In addition, the volume change is associated with the swelling material expressed as a weight gain of the cellulose polymer. Molecular modeling using Accelrys Materials Studio allowed us to open a new horizon and is helpful for understanding cellulose-water interactions.