In order to achieve multifunctional adhesive materials
with water
and salt tolerance, it is crucial to understand the electrostatic
mechanism of nanoconfined polyelectrolytes (PEs) with specific monomer
sequences. Here, using density functional theory (DFT), self-consistent
field theory (SCFT), and molecular dynamics (MD) simulation, we analyzed
the microstructures of sequence-defined PEs confined in a nanoscale
slit and the relationship between sequences and the attractive forces
induced by the nanoconfined PEs. Among three sequence-defined (alternating
[A], tapered [T], and reversely tapered [R] sequence) PEs, due to
the formation of stable multibridge conformations, [A]-sequence PEs
induce the strongest attractive forces even in the case with high
salt concentrations, i.e., the best salt tolerance. It is worth emphasizing
that salt enhancement of attractive forces occurs in systems with
[A]-sequence PEs due to the screening of repulsive interactions between
PE chains. In contrast, in systems with [T]-sequence PEs, the shielding
of the attractive interactions between surfaces and charged monomers
significantly attenuates the attractive forces between surfaces at
high salt concentrations. In addition, the strength of attractive
forces can be regulated by block number N
b. At high charge fractions such as f
c = 0.5, the attractive forces induced by [A]-sequence PEs become
stronger with N
b, while at low charge
fractions such as f
c = 0.2, the attractive
forces vary nonmonotonically with N
b due
to the electrostatic correlations.