Adhesion and
nanotribology of biofibres
Niklas Nordgren, Hanna Lönnberg, Eva Malmström, Linn
Carlsson and Mark W. Rutland
Royal Institute of Technology Stockholm Sweden
And YKI, Institute for Surface Chemistry, Sweden
[email protected]
CENTRUM FÖR BIOMIMETISK FIBERTEKNOLOGI
KTH Biotechnology
Umeå Plant Science Center
KTH Fiber and Polymer
KTH Surface and Corrosion Science
Innventia
The Colloidal Probe Technique
Photodetector
Laser
Cantilever
Probe
Piezo-scanner
Ducker, W. A.; Senden, T. J.; Pashley, R. M. Nature (London, United Kingdom) 1991, 353, 239-41.
Atomic Force Microscope
Cantilever functionalisation
• Fibre-Fibre geometry
• SiO2, polymers
• Gold
H. Mizuno, M. Kjellin, N. Nordgren, T. Pettersson, V. Wallqvist, M.
Fielden, M.W. Rutland, Australian Journal of Chemistry 59 (2006)
390-393.
Cellulose
Rutland, M. W., A. Carambassis, G. A. Willing and R. D. Neuman (1997). "Surface force measurements between cellulose surfaces using scanning probe
microscopy." Colloids and Surfaces, A: Physicochemical and Engineering Aspects 123-124: 369-374.
Superlubricity using repulsive vdW forces
“Switching off friction”
Effects of xyloglucan adsorption to cellulose
XG added
Without XG
• Increase adhesion between “fibres”
• Xyloglucan reduces friction up to 75%
Improved paper strength
Improved paper formation
Stiernstedt, J.; Brumer, H., III; Zhou, Q.; Teeri, T. T.; Rutland, M. W. Biomacromolecules 2006, 7, 2147-2153.
Christiernin, M.; Henriksson, G.; Lindström, M. E.; Brumer, H.; Teeri, T. T.; Lindström, T.; Laine, J.
Nordic Pulp & Paper Research Journal 2003, 18, 182-187.
But what do we mean by adhesion?
Work of adhesion W123
The work required to separate two different materials (1 and 3) in a
medium 2. Two unit surfaces are created and one destroyed.
W123= γ12 + γ23 - γ13
1
1
γ
12
γ
13
3
“van der Waals forces”
2
3
So how can adhesion be time dependent?
•Molecular rearrangement at interface - polymer diffusion
•Mechanical effects/Viscoelastic efects (rate of separation)
•Slow Deformation – increased contact area.
A. Plunkett and M. W. Rutland. Dynamic adhesion of grafted polymer surfaces as studied by surface force measurements.
urnal of Adhesion Science and Technology 16, 983-996 (2002)
A. Plunkett, S. Rodner, L. Bergstrom and M. W. Rutland. Surface forces and characterization of glass surfaces bearing grafted polymers: solvent dependence.
rnal of Adhesion Science and Technology 16, 965-981 (2002)
Bridging Adhesion
The case of xyloglucan modified cellulose surfaces (collab with Brumer, Teeri)
1
epulsive steric
orce as surfaces
pproach
2
Adsorbed
molecules
compressed
3
Some molecules
attach to 2
surfaces
4
Adhesion on
separation due
to bridging
What sort of adhesion mechanisms occur in Bio-nanocomposites?
epends on nature of interface!
•Unmodified cellulose - polymer matrix -> well defined interface -> van der Waals.
No mechanical contribution to adhesion.
fibril modified with matrix compatibilising polymer then better adhesion, but no
onger have a “surface”!!!
n this case the adhesion is provided by penetration of the compatibilising
olymer into the surrounding matrix
Sacrificial bonds and hidden lengths in natural biocomposite materials
Shell
Bone
Teeth
Schematic figure of the internal microstructure of a gastrolith. The mineral (calcium
carbonate) content has been reduced to emphasize the organic matrix (chitin and
proteoglycans) more clearly.
Analysis of adhesion data reveals mechanisms
mechanisms
Representative SEM images together with the chemical composition, estimated from EDS data
of the native gastrolith (A) and after 1 (B) and 16 (C) hours of demineralization
Mizuno, Pai, Thormann, Rutland, Bergström
Manuscript
1a)
2a)
Native
Native
1b)
2b)
Heavily demineralized
1c)
Deposited proteoglyc
Heavily demineralized
2c)
Deposited proteoglyc
Interfacial properties for cellulose based nanocomposites
•
Study the role of chemical grafting on adhesion and friction between fibre
and matrix material.
Grafting of poly(ɛ-caprolactone) (PCL
via Ring Opening Polymerization
Nordgren, N.; Lönnberg, H.; Hult, A.; Malmström, E.; Rutland, M. W., ACS Applied Materials and Interfaces 2009, 1, 2098-2103
Time and Temperature - end grafted from PCL on cellulose
20 °C
60 °C
Increased chain-chain entanglements
Stronger fiber-fiber bonding!
Adhesion energy
Diffusion controlled chain interactions
Higher Rate at increased Temperature – higher polymer mobility
Problem solved!!!
• Adhesion depends on penetration of grafted chains
into matrix.
• Depends on both time in contact AND temperature more mobile chains penetrate further.
• NO BRAINER…….
Follow up study:
Linn Carlsson and Niklas Nordgren
3 different Mw have been successfully grafted from the cellulose spheres (confirme
by ATR-FTIR).
Monomer conversion
Mw
(NMR)
(THF-SEC)
31%
9163
1.2
66%
34205
1.5
95%
54900
1.9
Investigate the effect of PCL graft length
(Mw) on the dynamic adhesion. Are the
thermal trends retained?
PDI
(THF-SEC)
Problem solved?
Define Dmax
Maximum pull-out distance
•Dmax increases with graft
length
•ie related to contour length?
Polymer diffusion- entanglement effects
Primitive path fluctuations
Pinned reptation
Also known as “breathing modes”
Except……..
20°
Dmax increases with T for a
given MW!!
•The number of bridges
increases with T but their
length is the same at each T.
•Not consistent with random
penetration of coils.
60°
Tentative explanation
• The polymer is not purely amorphous but has
crystalline and amorphous regions below the melting
point and above Tg.
• As the temperature is raised the size of the
amorphous regions increases, and penetration into the
matrix is determined by the size of the amorphous
region.
• This appears to be physically reasonable and would
explain the results but may lead to history effects the sizes of the domains may well depend on number
of heating cycles, heating rates etc
• An alternative, and related explanation is that it is the
outermost layer of the matrix which is amorphous and
the thickness of this layer controls the penetration
depth.
Probing polymer/grafted surfaces
Effect of chitosan
pH 3
with chitosan
neat cellulose
Effect of chitosan
pH 3
Amonton’s law:
μ = FFriction / FLoad
3/5-fold reduction in
with chitosan
Hydrated “cushion”
II
neatI cellulose
Route for top-down grafting of XG to gold
QCM crystal
Acknowledgments
Collaborators
Niklas Nordgren
Harry Brumer, Monika Österberg, Derek G. Gray, Janne
Laine, Paula Eronen, Hanna Lönnberg, Anders Hult,
Hiroyasu Mizuno, Mikael Kjellin, Adam Feiler, Qi Zhou,
Torbjörn Pettersson, Jens Eklöf, Johanna Stiernstedt, Lars
Wågberg and Eva Malmström
Funding
Swedish Research Council, Swedish Foundation for Strategic
Research (SSF) and Biomime, the Swedish Centre for Biomimetic
Fiber Engineering, BiMaC, the Biofibre Materials Centre at KTH.
Xyloglucan in the cellwall
Xyloglucan (XG)
Xylogl
ucan
beta(1-4) glucan-based polysaccharide
XET
Jocelyn K.C. Rose and Alan B. Bennett
trends in plant science
reviews
May 1999, Vol. 4, No. 5
Xyloglucan endotransglycosylase (XET)
catalyses cleavage and re-attachment of XG-chains
Interaction forces
Cellulose sphere
Cellulose sphere
Spincoated NMMO/DMSO film
Spincoated NMMO/DMSO film
annealed
Nanocrystalline film
Friction
25
a)
20
Friction force (nN)
a)
b)
c)
b)
c)
15
d)
e)
Cellulose colloid
Spincoated NMMO/DMSO
Spincoated NMMO/DMSO
annealed
Nanocrystalline film
Silica
d)
10
e)
Does the change in friction depend
on surface roughness or the
chemical nature of the substrates?
5
0
0
5
10
15
20
Load (nN)
25
30
35
Effect of xyloglucan adsorption
no additive
with xyloglucan
The effect on friction arising from either changes in surface chemistry
or roughness can be decoupled!
Top-down grafting of XG monitored by QCM
XG-SH (20ppm)
neat XG (20ppm)
Structure of the xyloglucan layer
XG
XG-SH
Enzymatic hydrolysis of XG monitored by QCM
grafting
digestion
endo-xyloglucanase (100ppm)
Friction between cellulose and model surface
After digestion
Gold
+ Xyloglucan
Imaging and surface roughness
Gold
2 × 2 µm
+ Xyloglucan
2 × 2 µm
rms = 0.93 nm
µ = 0.49
After digestion
2 × 2 µm
rms = 0.67 nm
µ = 0.317
rms= 3.1 nm
µ = 0.57
Surface roughness vs Friction
no additive
with xyloglucan
• Increasing friction of the digested brush due to increase in roughness
Adhesion
• Cellulose specificity retained