Polymer and Colloid ScienceGroup
• People• Research Activities• Collaborations• Output• Funding• Selected Presentations
IESL:03/ 2006
• MS-Students:N. Gomopoulos, N. Koumakis, P. Voudouris
• Five diploma work Students
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,
• 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: – 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
• Examples of
Over the Globe
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)
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. Marranzas5. Demokritos: T. Vourlinos D. N. Theodorou
international national collaborations
Selected Presentations
1. Polymers• Responsive Brushes• Control Processing (through macromolecular
architecture)
2. Colloids• Vitrification and flow of colloidal glasses
and gels• Hypersonic phononic crystals
Light scattering in the evanescent geometry
ki=kev
kfq
Z
Intensity
ki=kev
kfq
Z
Intensity
PS brushes in good solvent
Polymer Brush Dynamics
G. F., Science 1996
Responsive Brushes
Bad
Good
PS brushes in marginal solvent(cyclohexane)
T
10-6 10-5 10-4 10-3 10-2 10-1 100 1010.0
0.5
1.0
C(q
,t)
t [s]
32 36 40 440
2
410-5
10-3
10-1
I1
I2
1
2
I (a
. u.)
T (oC)
(s)
G. Yakubov, PRL 2004
V.Michailidou Macromolecules 2005
Rheology of Branched Polymers
• Seniority Rules: Outer branches relax first. Separated in time relaxation processes.
• Mean Field tube model.
-2 0 2 4 6 82
3
4
5
6
7
-1
0
1
2
3
log(aT/(rad s-1))
log(
G'/P
a,G
"/P
a)
Arms RelaxationBackbone Relaxation
log(tan)Seg
men
tal R
elax
atio
n
Vitrification and flow of colloidal glasses and gels
Effects of Interparticle InteractionsFrom Hard Spheres to Repulsive (soft) and Attractive Systems
Hard spheres Attractive spheres (Depletion attraction: Hard sphere-polymer mixtures)
Soft Spheres Multiarm stars
Light Scattering Echo + RheologyDynamic Light scattering under oscillatory
shear
t=0 t=T/2 t=T
Peaks in g(2)(t) (echoes) => elastic (reversible) response of the sample
0.00 0.01 0.02 0.03 0.04 1.30 1.32 1.340.0
0.5
1.0
no shear
Hars sphere glass
t (s)10-4 10-2 100 102
1.0
1.5
2.0
g(2) (
t)
t (s)
No shear (multispeckle) 1 Hz Shear
8% 45% 100% 200%
G. Petekidis et al. Faraday Discuss. (2003)
vertical liftingdeposition
dry colloidal crystal
liquid infiltration
blow off excess liquid
infiltrated colloidal crystal
self-assembling and infiltration procedures
J.Wang,U.Jonas
0.000 0.005 0.010 0.015 0.020 0.0250
1
2
3
4
5
6
7
8
256 nm 307nm
q (nm-1)
Fre
qu
en
cy (
GH
z)
Bragg gap
0.0
0.4
0.8
1.2
LL
a/2c
-15 -10 -5 0 5 10 150,0
0,2
0,4
0,6
0,8
1,0
1,2
Inte
nsity
(a.
u.)
f (GHz)
PS opals Size around 260nm
1.Dry Opals particle vibrations(elastic constants)
W. Cheng J.C.P (2005),M.Faatz Langmuir(2005)
Music of Spheres
Perspectives (research character)
Molecular Objects
Design Desired Function
Advanced Fields
eg. PolymersColloids
Antagonistic Forces,
Selection
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