Hemicelluloses at Interfaces: Some Aspects of the Interactions - The Nanoscience and Technology of Renewable Biomaterials - page 154

et al . 2003). The most widely used calibration methods determine the change in the
resonance frequency due to added mass (Cleveland et al . 1993), record the thermal
noise (Hutter and Bechhoefer 1993), or use an accurately calibrated reference cantilever
(Torii et al . 1996). The distance between the tip and the sample cannot be determined
directly. For presenting the interaction force as a function of tip-sample separation, the
distance is inferred from the raw data by adding the cantilever deflection to the sample
position. In this way the force can be plotted as a function of relative separation in a
force curve.

6.4 Experimental

6.4.1 Materials

6.4.1.1 Adsorption Experiments

QCM-D crystals. The sensor crystals used as a substrate for the model film coatings
and in the QCM-D experiments were AT-cut quartz crystals supplied by Q-sense AB,
Gothenburg, Sweden with a resonance frequency f 0 ≈ 5 MHz and a sensitivity constant

0 . 177 mg m − 2 Hz − 1 . The crystals were spin-coated with polystyrene by the sup-
plier. The polystyrene surface was hydrophobic, the contact angle values of pure water
on the crystal surface were 95 ◦ ±

C ≈

2 ◦ (Tammelin et al . 2006b).

Cellulose model film. Trimethylsilyl cellulose (TMSC) dissolved in chloroform was
deposited on the polystyrene coated QCM-D crystal using Langmuir-Schaefer technique
as described by Tammelin et al . (2006b). TMSC was hydrolyzed back to cellulose with
acid hydrolysis according to Schaub et al . (1993).

Mixture of dissolved hemicelluloses. Hemicelluloses used in the adsorption experiments
were isolated from the hexane extracted TMP by using the procedure described by
Thornton et al . (1994). Dissolved hemicellulose fractions were isolated from unbleached
and peroxide bleached TMP. The monosaccharide composition of the aqueous hemicel-
lulose fractions determined by gas chromatography is listed in Table 6.1. The fractions
from unbleached and bleached TMP were anionic with a charge density of 0.51 meq g − 1
and 1.38 meq g − 1 , respectively. Charge densities were determined by titration with a
cationic polyelectrolyte (1 meq l − 1 pDADMAC, M w < 300 kDa), using a particle charge
detector (M utek PCD 03, Germany) to indicate the end-point.

GGM (charge density 0.09 meq g − 1 , weight average

O-acetyl-galactoglucomannan.

M w ≈ 50 kDa with unimodal M w distribution analyzed by size exclusion chromatogra-

phy (SEC) was isolated from the mixture of TMP derived dissolved hemicelluloses by
the ultrafiltration technique described by Willfor et al . (2003).

Pectin. Pectin samples with a M w comparable to pectin found in spruce were pre-
pared from commercial citrus fruit pectin (Sigma-Aldrich Chemie BmbH, Germany) by
alkaline hydrolysis. The reaction mixtures were cooled to room temperature, acidified,
concentrated in a vacuum rotor-evaporator and freeze-dried. The charge density of the
final product was 2.1 meq g − 1 . The weight average M w was

≈ 12 kDa with a unimodal

M w distribution analyzed by SEC.