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Francesco Sciortino

Gelling on heating. A patchy particle story. Francesco Sciortino. http://glass.phys.uniroma1.it/sciortino/. Outline of the talk Mini-review on competitive interactions (chaining/branching, intra-inter bonding) A patchy particle model that gels on heating (S. Roldan, F. Smallenberg, W. Kob)

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Francesco Sciortino

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  1. Gelling on heating. A patchy particle story Francesco Sciortino http://glass.phys.uniroma1.it/sciortino/

  2. Outline of the talk Mini-review on competitive interactions (chaining/branching, intra-inter bonding) A patchy particle model that gels on heating (S. Roldan, F. Smallenberg, W. Kob) A possible DNA implementation (F. Romano)

  3. 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.

  4. Long range repulsion – short range attraction (charged colloids in the presence of a depletant) Suppress the phase separation in favor of a cluster phase A. Stradner, H. Sedgwick2, F. Cardinaux, W.C. K. Poon, S. U. Egelhaaf & P. Schurtenberger Nature 432, 492-495 (2004) | Campbell, A. I.; Anderson, V. J.; van Duijneveldt, J.; Bartlett, P. Phys. ReV. Lett. 2005, 94, 208301. S. Mossa, FS, P. Tartaglia, E. Zaccarelli Ground-state clusters for short-range attractive and long-range repulsive potentials Langmuir 20, 10756-10763, 2004

  5. Tlusty-Safram, Science (2000) Dipolar Hard Spheres… competition between chaining and branching Camp et al PRL (2000)

  6. 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 Chains win at low T Branching wins even at low T Chains win at low T Branching wins even at low T

  7. Branching at finite T ? Entropy ! Which Entropy ? Bonding Volume Entropy and “configurational” Entropy

  8. A patchy model with a “pinched” phase diagram B/A =0.37 J. Russo, et al Reentrant Phase Diagram of Network Fluids Phys. Rev. Letts. 106, 085703 (2011)

  9. How do we form an equilibrium gel ? reducing “valence” Small Valence The essence of the gel state of matter

  10. E. Bianchi, J. Largo, P. Tartaglia, E. Zaccarelli, FS Phase diagram of patchy colloids: towards empty liquids Phys. Rev. Lett. 97, 168301, 2006 Stable also against crystallization ! (limited valence + flexibility)

  11. DNA gels (Cerbino, Rovigatti talks) Limited valence + flexibility

  12. How do we break a gel ? Competing interactions…. Add a new species that compete for the bonding sites Network Blocked particle 2AA 4AB AB< AA /2

  13. How to stabilize the network: Entropy Bonding volume AA >> Bonding volume AB

  14. Forming and melting the gel ! Gel bonds Blocking bonds

  15. Low and high T Intermediate T

  16. Wertheim theory... different densities.... Parameter-free Theory Simulation

  17. Two-component phase-diagram .... Wertheim theory (black)... MC simulation (2SUS) (red)

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

  19. Can we realize this with the Biffi et al DNA particles ? (Roberto Cerbino’s talk) STAR-ARM-3’-CGATCG-5’ (Flavio Romano)

  20. Can we realize this with the Biffi et al DNA particles ? STAR-ARM-3’-CGATCGGG-5’ 3’-CCCG-5’ Blocking sequence AA-bonding: 6 bases paired STAR-ARM-3’-CGATCGGG-5’ STAR-ARM-3’-CGATCGGG-5’ AB-bonding: 4 bases paired STAR-ARM-3’-CGATCGGG-5’ 3’-CCCG-5’ (Flavio Romano)

  21. Nupack Evaluations: www.nupack.org Blocking bonds Gel bonds Gel bonds Blocking bonds

  22. How can we increase the entropic cost of blocking ? 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’ 5’-ACTCGC-3’ STAR-ARM-3’-TGAGCGTACGCAAT-5’ AB-bonding: 12 bases paired 5’-GCGTTA-3’ (Flavio Romano)

  23. AA-bonding: 8 bases paired AB-bonding: 12 bases paired

  24. Nupack Evaluations: www.nupack.org Gel bonds Blocking bonds

  25. 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)

  26. 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

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