Xylan Adsorption on Cellulose Model Films & Influence on Bond Strength Experiments Conducted in Context of My Master Thesis at the Solid State Physics Institute of TU Graz Siegfried Zöhrer szoehrer@sbox.tugraz.at 16.12.2013
FTIR spectroscopy of water-swelled & dried films Cellulose model films Tensile tests with xylan adsorbed films QCM-D analysis of xylan adsorption 2
1. FTIR spectroscopy of water-swelled & dried films Cellulose model films Tensile tests with xylan adsorbed films QCM-D analysis of xylan adsorption 3
1. FTIR spectroscopy of water-swelled & dried films Cellulose model films Tensile tests with xylan adsorbed films 2. QCM-D analysis of xylan adsorption 4
1. FTIR spectroscopy of water-swelled & dried films Cellulose model films 3. Tensile tests with xylan adsorbed films 2. QCM-D analysis of xylan adsorption 5
Cellulose Anhydroglucose units are linked to form a strictly linear homopolymer chain cellulose At the positions 2, 3 and 6 hydroxy groups are attached, which are free for reactions The DP is between 3000 and 15000 Intermolecular hydrogen bonds build crystalline domains 6
Xylan Hemicellulose is a collective term for a mixture of polysaccharids with different configurations Xylose is the main building block for the hemicellulose called xylan In contrast to cellulose, xylan has a branched structure, which makes it amorphous Molecular weight and DP (50 to 200) lower 7
Fabrication of cellulose model films TMSC-toluene solution Concentration: 5 g/l Mixed over night TMSC Source: Micro-crystalline cellulose Degree of substitution: 2.8 to 3 Supplier: OMPG 8
Fabrication of cellulose model films Si-wafer Thickness: (675±25) μm Type: P Dopant: Bor Orientation: <100> Square-cut 1 or 4 cm² pieces Cleaned with Acetone/Isopropanol Regeneration HCl 10 % about 1 ml in small petri dish 10 min Spincoating 3500 to 4000 rpm about 80 or 160 ml 60 s 9
Swelling & drying of model films Swelling Beaker with distilled water About 12 hours Drying Rapid-Köthen sheet dryer 4 hours, 0.1 bar, 92 C Cellulose Silicon Teflon 2 swelled samples Paper 10
FTIR spectroscopy Bruker ifs 66 v/s with a SiC glowbar and a Mercury Cadmium Telluride detector cooled by liquid nitrogen Sample chamber and optical setup evacuated by a rotary vain pump hν 74 P1 & P2 4 model films with 8 stacked cellulose layers ( 180 nm) Sample Measurements of model films in transmission and reflection before and after swelling & drying 30 P1 Background measurements with 1 respectively 2 (on top of each other) blank si-wafer pieces hν Sample P2 11
P-polarized spectra in transmission C-H bending O-H in plane deformation CH2 rocking C-O-C valence vibration C1 C-O-C asymmetric valence vibration C-O valence vibration C6 Ring asymmetric valence vibration Skeletal vibrations involving C-O stretching C-O stretching 12
P-polarized spectra in transmission C-H bending O-H in plane deformation CH2 rocking C-O-C valence vibration C1 C-O-C asymmetric valence vibration C-O valence vibration C6 Ring asymmetric valence vibration Skeletal vibrations involving C-O stretching C-O stretching 13
P-polarized spectra in transmission 14
QCM - introduction The quartz crystal is oscillating in thickness shear mode (shear oscillations parallel to the surface) There are several crystal cuts which have very low temperature dependence (like the AT-cut ) An applied voltage over an AT-cut quartz crystal induces a shear strain in the quartz 15
QCM with dissipation The QCM-D technology measures the frequency (f) and dissipation (D) of the freely oscillating quartz crystal after excitation The dissipation factor quantifies the damping in the system and provides information about conformational changes and softness/rigidity (viscoelasticity) of the molecules studied Output signal 16
Sauerbrey equation The resonance frequency of the mechanical oscillation responds very sensitively to the adsorption of any material upon the resonator surface The Sauerbrey equation correlates changes in the oscillation frequency of the crystal with the mass deposited on it It is valid for rigid and evenly distributed layers if the frequency change is small (Δf / f < 0.05) For quantitative analysis of soft layers, viscoelastic modeling is needed Overtone 17.7 ng Hzˉ¹ cmˉ² for a 5 MHz crystal 17
QCM-D measurement setup 4 quarz crystals with spincoated single layer of cellulose (same routine) Measurement during H2O-D2O exchange Measurement during xylan adsorption Q-Sense E4 with flow module, supports 4 parallel measurements Xylan solution 0.5 g/l, ph=8 IS=1M+1mMol NaCl 18
QCM-D H2O-D2O exchange 19
QCM-D H2O-D2O exchange 20
QCM-D xylan adsorption 21
QCM-D xylan adsorption 22
Xylan adsorption - Sauerbrey mass 23
Tensile tests of xylan adsorbed films 1 layered 1 cm² cellulose model films Swelled in water and xylan solution Dried in sheet dryer - followed by 1 day storage in climate chamber Tensile tests done with a Freeman Technology powder rheometer Before the actual test, the piston slowly moves downwards until 40 N are reached The device records the force and distance 5 times a second Calibration measurement with glued samples in case energies are needed Rheometer piston Socket Double sided tape Sampl e 24
Tensile tests of xylan adsorbed films 25
Tensile tests of xylan adsorbed films 26
Conclusions Binding together 2 cellulose model films through swelling & drying does not change their IR absorption peaks significantly The xylan adsorbed in 30 minutes on a thin (about 25 nm) cellulose model film is in the magnitude of 50 ng per cm² Filtering the solution changes the adsorption behavior, but not the amount of xylan adsorbed after rinsing This type of xylan adsorbed films bound together through swelling & drying can withstand a tensile force up to 18 N Filtering the xylan solution showed no effect in tensile tests 27
Outlook Tensile tests with water rinsed xylan adsorbed films Tensile tests with different parameters (e. g. ph of xylan solution) Estimate the water amount in the model films through viscoelastic modeling 28
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