Workshop on Soft Matter Self Assembly and Dynamics, January 910th, 2014 Hyderabad.
Simple models of competitive interactions in
soft-matter: re-entrant liquids and gels on
heating
Francesco Sciortino
http://glass.phys.uniroma1.it/sciortino/
Outline of the talk
Unconventional Gas-Liquid Phase
Behaviors. Re-entrant liquids (J. Russo,
L. Rovigatti, J. Tavares, Texeira, M. Telo
da Gama)
A patchy particle model that gels on
heating (S. Roldan, F. Smallenberg, W.
Kob)
A possible DNA implementation (F.
Romano)
Unconventional (gas-liquid) phase diagrams
standard
valence-dominated
Bianchi et al, PRL 97, 168301, 2006,
Gas-dominated
FS et al PRL 103, 237801 (2009)
liquid-dominated
Russo et al PRL 1a06, 085703 (2011);
Rovigatti et al Phys.Rev.Lett. 111, 168302 (2013)
Competitive Interactions
Modulate the entropy-enthalpy balance to stabilize
different local structures:
In this talk, the entropy-enthalpy balance promotes the
emergence of a structure controlled by energy (stable at
low T) which competes with a structure stabilized by
entropy at intermediate T.
Dipolar Hard Spheres…
Tlusty-Safram,
Science (2000)
competition between chaining and branching
Camp et al PRL (2000)
Can we reproduce this “pinched”
phase diagram with a simple
patchy model ?
Well defined pair-interaction potential
Exploit the Wertheim theory as a tool
J. M. Tavares, et al Mol. Phys. 107, 453
2009, Phys. Rev. E 80, 021506 2009
PATCHY PARTICLES THAT FORM CHAINS:
AA
PATCHY PARTICLES THAT FORM CHAINS:
AA
ADD BRANCHING POSSIBILITIES
AB
How the ground state looks like ?
Start from an infinite chain of AA bonds
How the ground state looks like ?
Start from an infinite chain of AA bonds
Splitting the chain in two parts costs AA
How the ground state looks like ?
Start from an infinite chain of AA bonds
Splitting the chain in two parts costs AA
Joining the two newly created ends provides a gain of -2AB
E=AA -2AB >0
AB/AA=0.5
Chaining wins
at low T
Chains win
at low T
Branching wins
even at low T
Branching wins
even at low T
Branching at finite T ?
Entropy !
Which Entropy ?
Bonding Volume Entropy and “configurational” Entropy
A patchy model with a “pinched” phase diagram
B/A =0.37
Russo et al PRL 106,
085703 (2011);
J. Russo, et al
Reentrant Phase Diagram of Network Fluids
Phys. Rev. Letts. 106, 085703 (2011)
Evolution of the phase diagram on modulating the branching strength AB
Effective temperature valence
Part II
How do we form an equilibrium gel ?
reducing “valence”
Small Valence
The essence of
the gel state of
matter
How do we break a gel ?
Competing interactions….
Add a new species that compete for the bonding sites
Network
Blocked particle
4AB
2AA
AB < AA /2
How to stabilize the network: Entropy
Bonding volume AA >> Bonding volume AB
Forming and melting the gel !
Gel bonds
Blocking bonds
Low and high T
Intermediate T
Projection in the 4-1 composition ratio (stochiometric mixture)
Can we design a system that does it ?
Experiments: DNA Hydrogels
Phase behavior of DNA hydrogels
Can we realize this with the Biffi et al DNA particles ?
STAR-ARM-3’(TGA)GCGTACGC(AAT)-5’
3’-ATTGCG-5’
3’-CGCTCA-5’
AA-bonding: 8 bases paired
STAR-ARM-3’(TGA)GCGTACGC(AAT)-5’
STAR-ARM-3’(TGA)GCGTACGC(AAT)-5’
AB-bonding:
12 bases paired
5’-ACTCGC-3’
STAR-ARM-3’-TGAGCGTACGCAAT-5’
5’-GCGTTA-3’
(Flavio Romano)
AA-bonding: 8 bases paired
AB-bonding:
12 bases paired
Nupack Evaluations: www.nupack.org
DNA
Gel bonds
Patchy model
Blocking bonds
Gel bonds
Blocking bonds
Conclusions
Competitive interactions: very powerful
concept for designing sensitive
structured materials
DNA constructs are
very versatile in this respect.
Hopefully, DNA re-entrant gels will be realized.
Waiting for experimental realization
(Milan-Rome)
Thanks to…
Emanuela Bianchi, Piero Tartaglia, Emanuela
Zaccarelli – Valence Phase Diagram
Flavio Romano (Oxford) - DNA gels
Walter Kob, (Montpellier), Sandalo Roldan, Frank
Smallenburg - Gel on heating
John Russo , J. M. Tavares, P. I. C. Teixeira, M. Telo da
Gama(Lisbon) - Chaining and Branching
Lorenzo Rovigatti - 2D SUS
Tommaso Bellini, Roberto Cerbino, Silvia Biffi, Francesca
Bomboi – experiments on DNA