We
apply Monte Carlo simulation to explore the adsorption of a
positively charged polyelectrolyte on a lipid monolayer membrane,
composed of electronically neutral, monovalent anionic and mulvitalent
anionic phospholipids. We systematically assess the influence of various
factors, including the intrinsic rigidity of the polyelectrolyte chain,
the bead charge density of the polyelectrolyte, and the ionic strength
of the saline solution, on the interfacial structural properties of
the polyelectrolyte/monolayer complex. The enhancement of the polyelectrolyte
chain intrinsic rigidity reduces the polyelectrolyte conformational
entropy loss and the energy gains in electrostatic interaction, but
elevates the segregated anionic lipid demixing entropy loss. This
energy-entropy competition results in a nonmonotonic dependence of
the polyelectrolyte/monolayer association strength on the degree of
chain rigidity. The semiflexible polyelectrolyte, i.e., the one with
an intermediate degree of chain rigidity, is shown to associate onto
the ternary membane below a higher critical ionic concentration. In
this ionic concentration regime, the semiflexible polyelectrolyte
binds onto the monolayer more firmly than the pancake-like flexible
one and exhibits a stretched conformation. When the chain is very
rigid, the polyelectrolyte with bead charge density <i>Z</i><sub>b</sub> = +1 exhibits a larger tail and tends to dissociate
from the membrane, whereas the one with <i>Z</i><sub>b </sub>= +2 can still bind onto the membrane in a bridge-like conformation.
Our results imply that chain intrinsic rigidity serves as an efficient
molecular factor for tailoring the adsorption/desorption transition
and interfacial structure of the polyelectrolyte/monolayer complex