OPOMNIK: IJS KOLOKVIJ, četrtek, 07. 05. 2015; ob 13. uri; prof. dr. Nigel B. Wilding

[Tanja Debevec]

Vabimo vas na 18. predavanje iz sklopa "Kolokviji na IJS" v letu 2014/15, ki bo v četrtek, 07. maja 2015, ob 13. uri v Veliki predavalnici Instituta »Jožef Stefan«  na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete tudi na naslovu http://www.ijs.si/ijsw/Koledar_prireditev, posnetke preteklih predavanj pa na http://videolectures.net/kolokviji_ijs. 

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prof. dr. Nigel B. Wilding

Univerza v Bathu, Bath, Velika Britanija

 

 

Samozdruževanje in fazno obnašanje vdrtih koloidov

Okrogli koloidni delci z majhno vdrtino lahko tvorijo verigaste skupke, pri čemer se vdrta stran enega delca tesno prilega izboklini drugega. V raztopini majhnih polimernih klobk, ki inducirajo deplecijsko interakcijo ter s tem nastanek vezi, pride do spontanega združevanja takih delcev. Prestavili bomo simulacije in teoretične raziskave tega procesa znotraj dveh modelov. V prvem smo študirali eksplicitno mešanico vdrtih koloidov v raztopini manjših kroglic. Morfologija nastalih verig je močno odvisna od velikosti vdrtine, pri čemer manjše spodbujajo razvejenost. V nasprotju s kroglicami s privlačnimi mesti tu perturbacijska termodinamična Wertheimova teorija ne ponudi kvantitativnega opisa polimerizacijskega prehoda. To pomanjkljivost smo povezali z zanemaritvijo pakiranja delcev in nato razvili popravljeno teorijo, ki bolje zajame obliko delcev in vodi do izboljšanega ujemanja s simulacijami. Nato smo simulacije mešanice preslikali na zelo poenostavljen model, ki omogoča študij sistema z mnogo delci. Z naraščanjem razmerja usmerjenih in neusmerjenih vezi postanejo kapljevinaste faze zelo nitaste, kritične točke pa se pomaknejo proti zelo majhnim gostotam. Dobljene kapljevine imajo bogato odprto strukturo z zanimivimi perkolacijskimi lastnostmi.

Predavanje bo v angleščini.

Lepo vabljeni!

 

 

 




We invite you to the 18th Institute colloquium in the academic year 2014/15. The colloquium will be held on Thursday, May 07, 2015 at 1 PM in the main Institute lecture hall, Jamova 39, Ljubljana. To read the abstract click  http://www.ijs.si/ijsw/Koledar_prireditev. Past colloquia are posted on  http://videolectures.net/kolokviji_ijs.

 

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prof. dr. Nigel B. Wilding

University of Bath, Bath, United Kingdom

 

 

Self-Assembly and Phase Behaviour of Indented Colloids

 

Spherical colloids with an indentation can chain via the process of lock-key binding whereby the indented side of one particle (the lock) fits neatly into the convex side of another (the key). Assembly occurs spontaneously when the colloids are immersed in a sea of much smaller  polymers leading to depletion interactions which promote bond formation. We report simulation and theoretical studies of this process in two models. Firstly we have considered an explicit mixture of indented colloids in a bath of much smaller hard spheres. The morphology of the chains that are formed depends sensitively on the size of the colloidal indentation, with smaller values additionally permitting chain branching. In contrast to the case of spheres with attractive patches, Wertheim's thermodynamic perturbation theory fails to provide a fully quantitative description of the polymerization transition. We trace this failure to a neglect of packing effects and we introduce a modified theory that accounts better for the shape of the colloids, yielding improved agreement with simulation. Secondly we have mapped simulations of the full mixture to a greatly simplified model allowing us to study the phase behaviour of large systems. As the ratio between directional and non-directional binding increases the liquid phases become very stringy with the critical points moving to very low density. The resulting liquids have a rich, open structure with interesting percolation properties.

 

Cordially invited!

 

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