"Step polymerization in various solvent conditions. A computer simulation approach using "Patchy Brownian Cluster Dynamics""
Who: Jean-Christophe Gimel (Micro and Nano-medicine laboratory, University Hospital in Angers)
Place: Donostia International Physics Center (DIPC). Paseo Manuel de Lardizabal, 4, Donostia
Date: Wednesday, 25 March 2015, 12:00
" Step polymerization in various solvent conditions. A computer simulation approach using "Patchy Brownian Cluster Dynamics" "
I will present a novel simulation technique derived from Brownian cluster dynamics used so far to study the isotropic colloidal aggregation . It now implements irreversible patchy interactions between particles . This technique gives access to static properties, dynamics and kinetics of the system, even far from the equilibrium. Particle thermal motions are modeled using billions of independent small random translations and rotations, constrained by the excluded volume and the connectivity. This algorithm, applied to a single polymer chain leads to correct static and dynamic properties, in the framework where hydrodynamic interactions are ignored.
By varying patch angles, various local chain flexibilities can be obtained. We have used this new algorithm to model step-growth polymerization under various solvent qualities. The polymerization reaction is modeled by an irreversible aggregation between patches while an isotropic finite squarewell potential is superimposed to mimic the solvent quality. In bad solvent conditions, a competition between a phase separation (due to the isotropic interaction) and polymerization (due to patches) occurs. Surprisingly, an arrested network with a very peculiar structure appears. It is made of strands and nodes. Strands gather few stretched chains that dip into entangled globular nodes. These nodes act as reticulation points between the strands. The system is kinetically driven and we observe a trapped arrested structure. That demonstrates one of the strengths of this new simulation technique. It can give valuable insights about mechanisms that could be involved in the formation of stranded gels.
 Babu, S., Gimel, J.-C., and Nicolai, T., Phase separation and percolation of reversibly aggregating spheres with a square-well attraction potential. Journal of Chemical Physics, 2006. 125(19): p. 184512.
 Prabhu, A., Babu, S.B., Dolado, J.S., and Gimel, J.-C., Brownian cluster dynamics with short range patchy interactions: Its application to polymers and step-growth polymerization. Journal of Chemical Physics, 2014. 141(2): p. 024904.
Host: Silvina Cerveny