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VERSION:2.0
PRODID:icalendar-ruby
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20261016T022846Z
UID:https://www.mpip-mainz.mpg.de/events/34450/536464
DTSTART:20230531T113000Z
DTEND:20230531T123000Z
CLASS:PUBLIC
CREATED:20230503T080322Z
DESCRIPTION: Gels with thermoreversible physical crosslinks show great prom
 ise for designing materials with tuneable rheology and self-healing proper
 ties. However\, many questions remain to be answered before the goal of ta
 iloring a gel’s macroscopic properties by controlling molecular scale pa
 rameters\, can be achieved. We show that considerable progress in this dir
 ection can be made by examining the behaviour of physical gels near the ge
 l transition with the help of Brownian dynamics simulations. Due to the sc
 ale-free and semidilute character of critical gels\, fully capturing their
  structure and dynamics requires the inclusion of associative interactions
  between sticky monomers\, solvent-mediated hydrodynamic interactions betw
 een all the monomers in a large simulation volume\, and time scales spanni
 ng several orders of magnitude. We have adapted Jim Swans’ algorithm for
  the efficient computation of hydrodynamic interactions in colloids to pol
 ymer chains\, making the simulation of the dynamics of physical gels at th
 e transition point tractable for the first time. Rheological properties su
 ch as the zero-shear viscosity and relaxation modulus are investigated sys
 tematically as functions of polymer concentration and binding energy betwe
 en associative sites. We show the structural emergence of a gel as a power
  law distribution of chain cluster sizes\, indicating a divergence of the 
 average cluster size. It is shown that a system-spanning network can form 
 regardless of binding energy at sufficiently high concentration. However\,
  the contribution to the stress sustained by this physical network can dec
 ay faster than other relaxation processes\, even single chain relaxations.
  If the polymer relaxation time scales overlap with short-lived associatio
 ns\, the mechanical response of a gel becomes “evanescent”\, decaying 
 before it can be rheologically observed\, even though the network is insta
 ntaneously mechanically rigid. In our simulations\, the concentration of e
 lastically active chains and the dynamic moduli are computed independently
 . This makes it possible to combine structural and rheological information
  to identify the concentration at which the sol-gel transition occurs as a
  function of binding energy. Further\, it is shown that the competition of
  scales between the sticker dissociation time and the single-polymer relax
 ation time determines if the gel is in the evanescent regime. Finally\, we
  compare the prediction of the concentration at the sol-gel transition by 
 a variety of different static and dynamic signatures of gelation.\nVortrag
 ender: Prof. Ravi Prakash Jagadeeshan
LAST-MODIFIED:20230503T080501Z
LOCATION:Max Planck Institute for Polymer Research\, Raum: Small Lecture Ha
 ll (1.003)
ORGANIZER;CN=Burkhard Duenweg:mailto:duenweg@mpip-mainz.mpg.de
SUMMARY:Evanescent gels and the sol-gel transition in associative polymer s
 olutions
URL;VALUE=URI:https://www.mpip-mainz.mpg.de/events/34450/536464
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