  We examine the interactions between polyelectrolytes (PEs) and uncharged
substrates at conditions corresponding to a dielectric discontinuity between
the aqueous solution and the substrate. To this end, we vary the relevant
system characteristics, in particular the substrate dielectric constant
$\varepsilon_{\rm s}$ under different salt conditions. We employ coarse-grained
molecular dynamics simulations with rodlike PEs in salt solutions with explicit
ions and implicit water solvent with dielectric constant $\varepsilon_{\rm w} =
80$. As expected, at low salt concentrations, PEs are repelled from the
substrates with $\varepsilon_{\rm s} < \varepsilon_{\rm w}$ but are attracted
to substrates with a high dielectric constant due to image charges. This
attraction considerably weakens for high salt and multivalent counterions due
to enhanced screening. Further, for monovalent salt, screening enhances
adsorption for weakly charged PEs, but weakens it for strongly charged ones.
Multivalent counterions, on the other hand, have little effect on weakly
charged PEs, but prevent adsorption of highly charged PEs, even at low salt
concentrations. We also find that correlation-induced charge inversion of a PE
is enhanced close to the low dielectric constant substrates, but suppressed
when the dielectric constant is high. To explore the possibility of a PE
monolayer formation, we examine the interaction of a pair of like-charged PEs
aligned parallel to a high dielectric constant substrate with $\varepsilon_{\rm
s} = 8000$. Our main conclusion is that monolayer formation is possible only
for weakly charged PEs at high salt concentrations of both monovalent and
multivalent counterions. Finally, we also consider the energetics of a PE
approaching the substrate perpendicular to it, in analogy to polymer
translocation.
