Modulating Microphase Separation of Lamellae-Forming Diblock Copolymers via Ionic Junctions

Abstract

We present a molecular dynamics simulation study investigating the phase behavior of lamellae-forming diblock copolymers with a single ionic junction on the backbone. Our results show qualitative agreement with experimental findings regarding enhanced microphase separation with the introduction of an ionic junction at the conjunction point, while further revealing nonmonotonic changes in domain spacing and order–disorder transition as a function of the electrostatic interaction strength. This highlights the dominant roles of entropic and binding effects of counterions under weak and strong ionic correlations, respectively. The location of the ionic junction is found to effectively modulate the charge distribution and chain conformation in the ordered domains; its presence in the middle of a block promotes folding of the block, leading to a smaller domain size. These findings demonstrate the interplay of ionic coupling with steric hindrance and chain end effects, which enhances our understanding of the delicate control over the microphase domain features.

Molecular Dynamics Simulations of Ion-Containing Polymers Using Generic Coarse-Grained Models

“…In one example, an ionic bead was added between the two blocks (Figure 4c). 152 This work aimed to provide guidelines for designing novel such systems that can be created experimentally with advanced synthesis strategies. Given the ions were part of the polymer chains and the effects of dielectric contrast were not the focus, there were no selective solvation interactions included; as in much of the prior ionomer work discussed above, the ionic bead connecting the two blocks was treated the same as a monomer bead except that it was charged, though in this case there were two chemical types of monomer beads.…”

“…(c) Bead–spring model of block copolymer with an ionic bead between two blocks as well as their morphologies and domain spacings at different Bjerrum lengths. Adapted with permission from ref . (d) Conductivity versus the fraction of low-polarity polymer in polymer blend electrolytes predicted by CG simulations and the corresponding simulation snapshots.…”

“…Bead–spring MD simulations have also recently been applied to study BCPs that include ions within their chains. In one example, an ionic bead was added between the two blocks (Figure c) . This work aimed to provide guidelines for designing novel such systems that can be created experimentally with advanced synthesis strategies.…”

Sub-3-Nanometer Domain Spacings of Ultrahigh-χ Multiblock Copolymers with Pendant Ionic Groups

“…Ion-containing polymer systems are a promising strategy for preparing high-χ multiblock copolymers, because the presence of ionic groups effectively increases the segregation strength between the blocks. ,− For example, our previous studies examined the phase behaviors of polyethylene-based sodium sulfosuccinate (PES x Na) multiblock copolymers, which contain short polar blocks with pendant Na + SO 3 – groups and nonpolar polyethylene blocks of x carbons ( x = 10–48). − Notably, these ion-containing multiblock copolymers microphase separate into ordered morphologies such as lamellar, gyroid, and hexagonally packed cylinder morphologies, and the smallest domain spacing is ∼2.2 nm in the lamellar and hexagonal morphologies of PES10Na. These results suggest that the nonpolar polyethylene blocks are highly incompatible with the polar ionic blocks, indicating a high χ in these PES x Na polymers.…”

Topological Effects Near Order–Disorder Transitions in Symmetric Diblock Copolymer Melts

“…Moreover, the ρ(z) of the systems could be To understand the effects of chain topology on the underlying conformational changes near the transition, we calculated the gyration tensor. 34 In Figure 3a− parameter 35,36 and defined as…”