Francesco SciortinoFrancesco Sciortino

Simple models of competitive interactions in soft-matter: re-entrant liquids and gels on

heating

Simple models of competitive interactions in soft-matter: re-entrant liquids and gels on

heating

http://glass.phys.uniroma1.it/sciortino/http://glass.phys.uniroma1.it/sciortino/

Workshop on Soft Matter Self Assembly and Dynamics, January 9-10th, 2014 Hyderabad.

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

Gas-dominatedliquid-dominated

valence-dominated

Bianchi et al, PRL 97, 168301, 2006,

Russo et al PRL 1a06, 085703 (2011); Rovigatti et al Phys.Rev.Lett. 111, 168302 (2013)FS et al PRL 103, 237801 (2009)

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…

competition between chaining and branching

Tlusty-Safram, Science (2000)

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

Splitting the chain in two parts costs AA

How the ground state looks like ? Start from an infinite chain of AA bonds

Chains win at low T

Branching winseven at low T

Splitting the chain in two parts costs AA

How the ground state looks like ? Start from an infinite chain of AA bonds

AB/AA=0.5

Chaining wins at low T

Branching winseven at low T

E=AA -2AB >0

Joining the two newly created ends provides a gain of -2AB

Branching at finite T ?

Entropy !

Which Entropy ?

Bonding Volume Entropy and “configurational” Entropy

B/A =0.37

J. Russo, et alReentrant Phase Diagram of Network FluidsPhys. Rev. Letts. 106, 085703 (2011)

A patchy model with a “pinched” phase diagram

Russo et al PRL 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 ValenceThe essence ofthe gel state ofmatter

How do we break a gel ?

Competing interactions….

Add a new species that compete for the bonding sites

AA AB

AB AA /2

Network Blocked particle

How to stabilize the network: Entropy

Bonding volume AA >> Bonding volume AB

Gel bonds

Blocking bonds

Forming and melting the gel !

Low and high T

Intermediate T

Projection in the 4-1 composition ratio (stochiometric mixture)

Slower

Slower

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’

STAR-ARM-3’-TGAGCGTACGCAAT-5’ 5’-GCGTTA-3’

5’-ACTCGC-3’

STAR-ARM-3’(TGA)GCGTACGC(AAT)-5’ STAR-ARM-3’(TGA)GCGTACGC(AAT)-5’

AA-bonding: 8 bases paired

AB-bonding: 12 bases paired

(Flavio Romano)

AA-bonding: 8 bases paired

AB-bonding: 12 bases paired

Nupack Evaluations: www.nupack.org

Gel bonds

Blocking bonds

Blocking bonds

Gel bonds

Patchy model

DNA

Conclusions

Competitive interactions: very powerfulconcept 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