Polymer and Colloid Science
Group
•
•
•
•
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People
Research Activities
Collaborations
Output
Funding
Selected Presentations
IESL:03/ 2006
PEOPLE
(current state)
• B. Loppinet, G. Petekidis (Researcher’s)
• G. Fytas, D. Vlassopoulos (Dept. Mat. Sci. Faculty Members)
• A. Larsen : Physics Technician
• Post Docs:
E. van Ruymbeke,
• PhD Students: M. Gianneli, M. Kapnistos, V. Michailidou,
M. Stiakakis, Cheng Wei,
• MS-Students:N. Gomopoulos, N. Koumakis,
P. Voudouris
• Five diploma work Students
• Visiting Scientists: T. Caremans (Leuven), E. Filippidi (Harvard),
J. Gapinski (Poznan), A. Kröger (Mainz),
K. Pham (Edinburgh), S. Roberts (N. Zealand),
E. Sanders (Eindhoven), T.Sanders (Eindhoven),
J. Stellbrink (Jülich)
Research Activities
• Problems:
–
–
–
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Soft Colloids: effective interactions, dynamics and rheology
Dynamics and non-linear rheology of colloidal glasses and gels
Dynamics of surface tethered polymers
Macromolecular architecture, self assembly and relaxation in
polymeric systems
– Laser induced concentration gradients in transparent polymer
solutions
– Phonons in soft structures
• Development of Experimental Tools
 EWDLS and combination with SPR
 Combination of DLS-Echo and Rheology
 FCS in Polymer Science
 BS of soft structures
Collaborations
Over the Globe
• Examples of
international
1. P. N. Pusey, Edinburgh (Faraday
Disc. 2004)
2. C. Likos, Düsseldorf (PRL 2003)
3. J. Rühe, IMTEK Freiburg (PRL 2004)
4. E. L. Thomas, MIT (PRL 2005)
5. MPIP (Mainz)
national collaborations
1. E. N. Economou, IESL (PRL 2003)
2. N. Vainos, EIE (Science 2002, JACS
2005)
3. N. Hadjichristidis (Macromolecules…)
4. ICEHT Patras: S. Yannopoulos,
B. Marranzas
5. Demokritos: T. Vourlinos
D. N. Theodorou
Selected Presentations
1. Polymers
• Responsive Brushes
• Control Processing
(through macromolecular architecture)
2. Colloids
• Vitrification and flow of colloidal glasses and gels
• Hypersonic phononic crystals
Polymer Brush Dynamics
Light scattering in the evanescent
geometry
PS brushes in good solvent
C(q,t)
1.0
PS-3
PS-5
PS-8
10
3.5
2.2
0.5
0.0
PS-3
PS-8
PS-5
-4
10
10
t(s)
G. F., Science 1996
-3
10
 (s)
Responsive Brushes
-1
10
-3
10
-5
1
2
I1
4
I (a. u.)
PS brushes in marginal solvent
(cyclohexane)
10
1.0
I2
2
0
32
36
o
40
44
Bad
C(q,t)
T ( C)
0.5
T
0.0
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
10
1
10
t [s]
Good
G. Yakubov, PRL 2004
V.Michailidou Macromolecules 2005
Rheology of Branched Polymers
log(G'/Pa,G"/Pa)
6
5
4
2
1
0
3
2
Segmental Relaxation
3
Backbone Relaxation Arms Relaxation
-2
0
2
4
-1
log(aT/(rad s ))
6
-1
8
log(tan)
• Seniority Rules: Outer
branches relax first.
Separated in time
relaxation processes.
• Mean Field tube model.
7
Vitrification and flow of colloidal
glasses and gels
Effects of Interparticle Interactions
From Hard Spheres to Repulsive (soft) and Attractive Systems
Hard spheres
Soft Spheres
Multiarm stars
Attractive spheres
(Depletion attraction:
Hard sphere-polymer mixtures)
Light Scattering Echo + Rheology
Dynamic Light scattering under oscillatory shear
t=0
t=T/2
t=T
Peaks in g(2)(t) (echoes) => elastic (reversible) response of the sample
Hars sphere glass
1.0
2.0
no shear
1.5
(2)
0.5
g (t)
No shear (multispeckle)
1 Hz Shear
8%
45%
100%
200%
0.0
0.00 0.01 0.02 0.03 0.04
1.30
t (s)
1.32
1.34
1.0
-4
10
-2
10
0
10
t (s)
2
10
G. Petekidis et al. Faraday Discuss. (2003)
self-assembling and infiltration procedures
vertical lifting
deposition
dry colloidal
crystal
liquid
infiltration
blow off
excess
liquid
infiltrated
colloidal
crystal
J.Wang,U.Jonas
Inelastic Brillouin Light Scattering
H.Kriegs(2003)
8
a/2c
1.2
Bragg gap
0.8
0.4
Frequency (GHz)
7
6
0.0

L
L
5
4
3
2
1
0
0.000
256 nm
307nm
0.005
0.010
0.015
-1
q (nm )
0.020
0.025
Scattering Geometry
Music of Spheres
1,2
PS opals
Size around 260nm
Intensity (a.u.)
1,0
0,8
0,6
0,4
0,2
0,0
-15
-10
-5
0
5
10
15
f (GHz)
1.Dry Opals
particle vibrations
(elastic constants)
W. Cheng J.C.P (2005),
M.Faatz Langmuir(2005)
Perspectives (research character)
Molecular
Objects
Design
eg. Polymers Antagonistic
Forces,
Colloids
Selection
Desired
Function
Advanced
Fields
Appropriate
Morphology,
Recognition
Phononic
Devices,
Sensors,
Motors
Future directions/needs
• Bio-functional surface architecture
(external collaboration: J. Rühe, J. Knoll)
• Understanding of self-assembly and
functions of bio-related systems
(collaborations: K. Tokatlidis, A. Mitraki, University of Crete)
• Single Macromolecule probing and
manipulation
Needs:
• Soft Matter theory/simulation
• Experimentalist in biorelated systems