Electrostatic interaction is widely
considered to be the main driving
force of the adsorption of polyelectrolytes (PEs) on an oppositely
charged surface. Therefore, the alteration of charge distribution
as a result of varying PE chain structures will directly affect the
performance of the adsorption behaviors in the system at a certain
monomer concentration. In this work, we studied the effects of chain
structure (chain length, N
m) as well as
sequence variables including charge fraction and blockiness on the
adsorption behaviors of block-PEs on an oppositely charged planar
surface in the salt-free system using PE-Poisson–Boltzmann
equations. Due to the complicated competitions among the translational
entropies of PEs and counterions, the conformational entropy of PEs,
and the surface attractive interactions, we find that the adsorption
amounts show rich behaviors. First, the adsorption amounts of charged
ζc and neutral ζn monomers both
show two-stage behaviors, that is, ζc and ζn drastically increase with N
m for
short chains but moderately increase to an asymptotic value for relatively
long chains. Second, the adsorption amounts of charged monomers show
non-monotonic behaviors (increase first then decrease) with charge
fraction. However, the adsorption amounts of neutral monomers monotonically
decrease with charge fraction. Finally, when chain length and charge
fraction are unchanged, the adsorption amounts of both neutral and
charged monomers are independent of blockiness. Moreover, we find
that overcharging can only appear when the bare surface charge density
is low enough, while charge reversal and inversion can be observed
in the entire range of the bare surface charge density with appropriate
conditions. Additionally, our results indicate that the strength of
charge reversal and inversion increases monotonically with chain length
and charge fraction, while it changes non-monotonically with blockiness.