Force Regulation by Sequence-Defined Polyelectrolytes

Abstract

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.

Nanoscale Hierarchical Structures Formed by Sequence-Defined Polycations and Homopolyanions for High Salt-Tolerance Adhesives

“…In this section, we will consider three types of representative SDPCs with fixed block numbers ( N b = 10), i.e., alternating [A], tapered [T], and reversely tapered [R] sequences. In the absence of short HPA chains, the peel force F peel induced by [A]-sequence PCs is the highest among those three types of SDPCs (Figure a) due to the formation of the most stable bridges between the surfaces . When the PEM structure is formed with the addition of short HPA chains (Figure c,d), the peel force is significantly enhanced (Figure b).…”

“…Moreover, a denser LBL structure will lead to a stronger adhesion. Due to the weakest decentralization effect of electrostatic attraction, , the monomer density profiles of both [T]-sequence PCs and HPA chains show the highest peaks (Figure d), which indicates that the most compact PEM structure is formed in this system. Therefore, the peel force induced by the [T]-sequence PCs and HPA mixtures is the largest.…”

“…Among the three types of SDPCs mentioned above, the systems with alternating sequence polycation ([A]-PC) can induce the strongest adhesion due to their ability to form stable multibridge conformations . In order to further improve the adhesive performance, the short HPA chains are added to the systems with 10­[A]-PC (reference to [A]-PC with a fixed block number of N b = 10).…”

“…Eqs , and are solved using Picard iteration. The more detailed theoretical formulas and numerical implementation can be found in Supporting Information and our previous work. , Once a solution is obtained, the grand potential of the system can be calculated as β W = F normale normalx − ∑ p = 1 P ∑ m = 0 N p ∫ normald boldr ρ p m ( r ) [ β Z p m e 0 ϕ false( boldr false) + δ scriptF e x / δ ρ p m false( boldr false) + 1 / N p ] + ∑ α ∫ normald boldr ρ α ( r ) [ β Z α e 0 ϕ false( boldr false) + δ scriptF e x / δ ρ α false( boldr false) + 1 ] …”

“…Eqs , and are solved using Picard iteration. The more detailed theoretical formulas and numerical implementation can be found in Supporting Information and our previous work. , Once a solution is obtained, the grand potential of the system can be calculated as …”