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Francesco Sciortino

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

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Francesco Sciortino

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  1. Workshop on Soft Matter Self Assembly and Dynamics, January 9-10th, 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/

  2. 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)

  3. Unconventional (gas-liquid) phase diagrams standard valence-dominated Bianchi et al, PRL 97, 168301, 2006, liquid-dominated Gas-dominated Russo et al PRL 1a06, 085703 (2011); Rovigatti et al Phys.Rev.Lett. 111, 168302 (2013) FS et al PRL 103, 237801 (2009)

  4. 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.

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

  6. 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, 4532009, Phys. Rev. E80, 021506 2009

  7. PATCHY PARTICLES THAT FORM CHAINS: AA

  8. PATCHY PARTICLES THAT FORM CHAINS: AA ADD BRANCHING POSSIBILITIES AB

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

  10. How the ground state looks like ? Start from an infinite chain of AA bonds Splitting the chain in two parts costs AA

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

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

  13. 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)

  14. Evolution of the phase diagram on modulating the branching strength AB

  15. Effective temperature valence

  16. Part II

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

  18. 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

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

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

  21. Low and high T Intermediate T

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

  23. Can we design a system that does it ?

  24. Experiments: DNA Hydrogels

  25. Phase behavior of DNA hydrogels

  26. 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’ 5’-ACTCGC-3’ STAR-ARM-3’-TGAGCGTACGCAAT-5’ AB-bonding: 12 bases paired 5’-GCGTTA-3’ (Flavio Romano)

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

  28. Nupack Evaluations: www.nupack.org DNA Gel bonds Patchy model Blocking bonds Gel bonds Blocking bonds

  29. 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)

  30. 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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