  In this work we investigated the question of how the molecular nature of the
dielectric media and the polymer-solvent dielectric mismatch affect the
collapse of a polyelectrolyte chain in solution by means of dissipative
particle dynamics simulations. First, we studied whether the explicit treatment
of dielectric media as polar beads instead of homogeneous dielectric background
results in a different system behavior. We showed that the explicit treatment
of polar beads facilitates the chain collapse, i.e. it occurs at smaller values
of the electrostatic strength parameter values ${\lambda}^2 \sim
Q^2/({\epsilon}kT)$. We believe that the main reason for such behavior is that
the dielectric response is in fact a collective effect, and the "effective"
dielectric permittivity is different from the bulk value when the charges are
close to each other and/or the density of the charges is high enough. This
implies that the value of ${\lambda}$ does not have a universal meaning due to
the small-scale effects related to the presence of polar species; therefore,
changing the total unit charge $Q$ or the temperature $kT$ is not equivalent to
changing ${\epsilon}$. Next, we investigated how the difference of the
dielectric permittivities of the polymer chain and solvent affects the
collapse. We showed the polar chain adapts less swollen conformations in the
polyelectrolyte regime and collapses easier compared to the case of non-polar
chain; the possible reasons for such behavior are discussed.
