STUDIES OF NATIVE CELLULOSE
STRUCTURE USING X-RAY RIETVELD ANALYSIS.
L.A. Lugovskaya, L.A.
Aleshina, A.S. Filatov, A.D. Fofanov, S.V. Glazkova and M.V. Podoinikova
Petrozavodsk State University, pr. Lenina 33, 185640
Petrozavodsk, Russia (LiubovL@psu.karelia.ru)
In this work the Rietveld method has been used for
analysis of structure of wood cellulose (pine and fir-trees), cotton cellulose,
and semi-finished items made of pine and fir wood. The X-ray experiments were
carried out using two diffraction geometries: transmission and reflection.
Diffraction patterns were obtained with Fe, Cu and МоKa radiation in automatic mode.
Calculated X-ray patterns were computed for four
models of the cellulose I structure: triclinic cell (Ia cellulose) and monoclinic cell (Ib cellulose)
with parallel up, parallel down and anti-parallel positional relationship of
two molecules.
Table: Unit cell parameters for theoretical models the calculated x-ray
patterns of which in the best way describe the experimental profiles.
|
Sample |
a, |
b, |
c, |
a¡, b¡, g¡ |
Model |
|
Cotton cellulose |
8,06 |
8,33 |
10,34 |
90, 90, 97,0 |
b1, antiparallel |
|
Pine
late wood, tangential section, |
8,09 |
8,17 |
10,34 |
90, 90, 96.4 |
b1, antiparallel |
|
Pine early wood, tangential section, |
7,91 |
8,17 |
10,34 |
90, 90, 97.0 |
b1, parallel down |
|
Bleached sulphate cellulose, (Finland) |
6,74 |
5,97 |
10,35 |
117, 113, 81.3 |
a1, parallel |
|
Bleached sulphate cellulose (FlashORION) |
6,74 |
5,94 |
10,36 |
117, 113, 81.3 |
a1 parallel |
|
Unbleached bisulphate fur-tree cellulose |
8,02 8,03 |
8,17 8,16 |
10,35 10,33 |
90, 90, 96.3 90, 90, 96.3 |
b1, parallel down b1, parallel up |
|
Unbleached sulphate pine cellulose |
6,72 |
5,97 |
10,37 |
117, 113, 81.8 |
a1 parallel |
It is shown that the structures of early and late
cellulose from pine wood is best described by a monoclinic unit cell. However
the packing of molecules in the cell and the values of the lattice periods are
different. The semi-finished items obtained from pine wood by sulphate cooking
are characterized by a single-chain triclinic elementary unit cell, of lower
symmetry. Consequently, the two-chain monoclinic elementary unit cell decays
during sulphate cooking. Bisulphate cooking does not result in a lowering of
symmetry, i.e. a two-chained monoclinic elementary unit cell is retained.
This study was financially supported by the Russian Foundation for Basic Research, Project No. 02-02-97504