Hemicelluloses at Interfaces: Some Aspects of the Interactions - The Nanoscience and Technology of Renewable Biomaterials - page 155

Table6.1 Monosaccharidecompositions(%)of the
dissolvedhemicellulosesderivedfromunbleachedand
peroxidebleachedspruceTMP.

Unbleached Bleached

Arabinose 2.7 3.7

Xylose 3.0 8.9

Rhamnose 3.2 9.0

Mannose 47.1 14.0

Galactose 14.3 10.6

Glucose 14.6 5.7

Galacturonic acid 14.2 46.7

Glucuronic acid 0.9 0.7

4- O -Me-glucuronic acid 0 0.6

Xylan. Xylan was commercial birch xylan from Roth (4- O -methylglucuronoxylan,

M w ≈ 100 as reported by the supplier) and it contained 7.8% 4- O -methyl-

α -D-glucuronic acid side groups. The same xylan was used in the cellulose-xylan force
measurements.
All other chemicals were of p.a. grade if not otherwise specified.

14 kDa, DP ≈

6.4.1.2 Force Measurements

Cellulose beads for the force measurements. The cellulose surfaces employed in the
AFM force measurements were crosslinked cellulose beads obtained from Kanebo Co.
(Japan). The degree of crystallinity of the beads was 5-35% and they consisted mainly
of type II cellulose (Carambassis and Rutland 1999). The diameter of the cellulose
beads changed by 5% to 20% during swelling (Paananen et al . 2003) and hence, fully
swollen beads were used in the experiments. The surface roughness of wet cellulose

m 2 beads was determined from AFM images (3 × 3 µ ×

with 512 512 pixels) and was

approximately 30 nm.

6.4.2 Methods

6.4.2.1 QCM-D Adsorption

QCM-D instrument. Adsorption of hemicelluloses (fractions isolated from unbleached
TMP and bleached TMP as well as pure GGM, pectin and xylan) on cellulose was studied
using a QCM-D instrument from Q-Sense, Gothenburg, Sweden (Rodahl et al . 1995).
Hemicellulose adsorption took place in an axial flow chamber (Q-Sense D300 system).
With QCM-D the changes in frequency and dissipation can be followed simultaneously
at the fundamental resonance frequency (5 MHz) and its overtones (15, 25 and 35 MHz).

Sample preparation. To avoid pH fluctuations in the QCM-D chamber during the
adsorption experiments, the samples of hemicelluloses except xylan samples were pre-
pared using an aqueous sodium acetate/acetic acid buffer solution with the ionic strength
of 10 mM (NaAc/HAc, pH 5.6).