Annual Report 2012 - Latvijas Universitātes Cietvielu fizikas institūts

exposure, show that the slow diffusion of particles at low effective temperatures (where
the attractions are much higher than the thermal energy) results in the formation of
small, ‘‘kinetically frozen’’ aggregates. On the other hand, aggregation does not occur at
high effective temperatures, where the attractions are comparable to the thermal energy.
In the intermediate range of effective temperatures, ‘‘fluctuating’’ aggregates form that
can be stabilized by applying light pulses of specific lengths and frequencies. The
aggregate sizes increase by increasing the packing fraction and the aggregates undergo
transition to a percolated ‘‘network’’ at high packing fractions. Light-control of interparticle
interactions can either inhibit or promote nucleation and growth, and can reduce
gel and glass formation.
THE KINETIC MONTE CARLO SIMULATIONS OF FLOW-ASSISTED
POLYMERIZATION
V.N. Kuzovkov,
Prateek K. Jha and M. Olvera de la Cruz (Northwestern University, Evanston, USA)
In collaboration with Northwestern University, Evanston, USA, we performed kinetic
Monte Carlo simulations on a model of a polymerization process in the presence of a
periodic oscillatory flow to explore the role of mixing in polymerization reactors.
Application of an oscillatory flow field helps overcome the diffusive limitations that
develop during a polymerization process due to an increase in the molecular weights of
polymer chains, thereby giving rise to high rates of polymerization. A systematic
increase in the flow strength results in a “dynamic” coil−stretch transition, leading to an
elongation of polymer chains. Reactive ends of stretched (polymer) chains react more
frequently than the reactive ends of coiled chains, which are screened by other
monomers of the same chain. There exists a critical flow strength for the efficiency of
polymerization processes. The kinetic Monte Carlo simulation scheme developed here
exhibit great promise for the study of dynamic properties of polymer systems.
Fig.16. Cover page of the ACS Macro Letters with the presentation of this paper.
70