Ball-milling Promoted Chemical Bonding between Cellulose and Plastics - Ball Milling Towards Green Synthesis: Applications, Projects, Challenges - page 206

Figure 9.2 Average structures of each solute over the initial (above) and the last
(below) 100 ps in the 1 ns calculation time. From left to right, malto
(from M1 to M6) and cello-oligosaccharides (from C1 to C6) from
monomer to hexamer, respectively.
Reprinted from ref. 3 with permission of Elsevier.
Intramolecular hydrogen bonding exerts a primary effect on stabilization
of the conformations of malto- and cello-oligosaccharides. Two definitions
of hydrogen bonds, (1) a distance between two oxygens of r 0.35 nm and (2)
an angle O-H O of 120-1801, make it possible to calculate the total number
of intramolecular inter-residue hydrogen bonds for the conformations of
malto- and cello-oligosaccharides (DP ¼ 2-6). Inter-residue hydrogen bonds
of interest occur more frequently with less fluctuation in cello- than in
malto-oligosaccharides, in accordance with the results of conformational
flexibility. Dominant hydrogen bonding between inter-residue O5-O3 0 , with
an occupancy rate of 65%, causes the rigid conformation of cello-oligo-
saccharides at the glycosidic linkage. In contrast, malto-oligosaccharides
have two modes of inter-residue hydrogen bonding of O2-O3 0 and O6-O6 0 ,
with occupancy rates of 35% and 8.3%, respectively, in accordance with a
helical conformation with a higher fluctuation on the side of O6 than
O2 or O3.
The rigid conformation of cello-oligosaccharides is further assisted
through the 1.3-1.5-times greater number of double hydrogen-bonded water
molecules as compared to malto-oligosaccharides. The double hydrogen-
bonded water molecules are located more around glycosidic linkages in
cello- than in malto-oligosaccharides. Therefore, conformations of cello- and