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

Inelastic Brillouin Light Scattering

H.Kriegs(2003)

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

Scattering Geometry

-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