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5th International Discussion Meeting on Relaxations in Complex Systems New results, Directions and Opportunities. Physical Gels and strong liquids. Wednesday … last talk. Francesco Sciortino. Outline. Irreversible (Chemical) Gelation in a simple model Thermoreversible (Physical) Gelation

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physical gels and strong liquids

5th International Discussion Meeting on Relaxations in Complex Systems

New results, Directions and Opportunities

Physical Gels and strong liquids

Wednesday … last talk

Francesco Sciortino

outline
Outline
  • Irreversible (Chemical) Gelation in a simple model
  • Thermoreversible (Physical) Gelation
  • Gels (strong liquids) and Glasses
  • Other gels…..(water, DNA-gels)
ivan hs gel

Irreversible Gelation

Ivan HS gel

Simple Model for Chemical Gels [with HS g(r)]

V(r

)

s

s+D

r

irreversible gelation f q
Irreversible Gelation fq

Signatures of percolation at fixed q

finite lifetime
Finite Lifetime….

V(r

)

s

s+D

r

See also Del Gado works

square well 3 width
Square Well 3% width

What on cooling ?

Generic Phase Diagram for Square Well (3%)

the quest
The quest

The quest for the ideal (thermoreversible) gel….model

1) Long Living (but reversible) bonds

2)No Phase Separation

Are 1 and 2 mutually exclusive ?

Long Bond

Lifetime

LowTemperature

Condensation

surface tension
Surface Tension

How to stay at low T without condensation ?

Reasons for condensation

(Frank, Hill, Coniglio)

Physical Clusters at low T

if

the infinite cluster is the lowest (free)energy state

How to make the surface as stable as the bulk (or more)?

The quest

n max on a bethe lattice
Nmax on a Bethe lattice

Nmax=12

Nmax=5

Nmax=2

E=0

E=-1

E=-Nmax

E=-Nmax

S.Sastry and E. La Nave

maximum valency
Maximum Valency

Geometric Constraint: Maximum Valency

V(r

)

SW if # of bonded particles <= Nmax

HS if # of bonded particles > Nmax

r

phase diagram
Phase Diagram

et al

NMAX-modifiedPhase Diagram

what is the gel dynamics in this model
What is the gel dynamics (in this model) ?
  • Bond lifetime (Arrhenius along isochores)
what is the gel dynamics in this model1
What is the gel dynamics (in this model) ?
  • Bond lifetime
  • R2 vs t (along isochores)
dynamic arrest lines
Dynamic Arrest Lines

The possibility of observing strong-liquid behavior intimately connected to reduction of bonding

colloidal gels molecular gels and dna gels
Colloidal Gels, Molecular Gels, …. and DNA gels

Four Arm Ologonucleotide Complexes as precursors for the generation of supramolecular periodic assemblies

JACS 126, 2050 2004

Palindroms in complementary space

conclusions
Conclusions…..
  • Gel propensity: Initial understanding of the ingredients requested to generate an “ideal” gel
  • Gels and Glasses (two different faces of the arrest dynamics). Percolation not seen…
  • Molecular and Atomic gels - Strong !
  • Interesting questions…. Where is the MCT line ?
slide26

C. De Michele, E. La Nave, P. Tartaglia, E. Zaccarelli (U. La Sapienza, Roma, Italy)I. Saika-Voivod (U. Saskatchewan, Canada)A. Moreno (Donostia International Center, Spain)S. Bulderyev (DMD code) (Yeshiva U., USA) S. Sastry (Bethe) (JNCASR, India)F. Starr (DNA-Gels) (Wesleyan U., USA)