Dependence of Block Copolymer Domain Spacing and Morphology on the Cation Structure of Ionic Liquid Additives

Abstract

We find that the topology of phase diagrams for block copolymer/ionic liquid (IL) blends and the scaling of the phase-separated domains are significantly influenced by the cation structure of the IL. We have varied the cation structure of bis(trifluoromethane sulfonyl)imide ILs and investigated the influence of these changes on the thermodynamics of blends with polystyrene-b-poly(methyl methacrylate). Effective χ parameters (χ eff ) were determined and used to plot phase diagrams, where significant differences were observed, suggesting that the balance of Coulombic and van der Waals interactions was influencing the topology of the phase diagrams. The relationship between IL structure and scaling of domain spacing was also investigated. These important findings shed additional light on the thermodynamic-driven properties of IL-containing block copolymers and have practical implications for how they can be used in nanotemplating or block copolymer lithography applications.

Microphase Separation of Ionic Liquid-Containing Diblock Copolymers: Effects of Dielectric Inhomogeneity and Asymmetry in the Molecular Volumes and Interactions between the Cation and Anion

“…For weakly charged polyelectrolytes with small inorganic ions, the effect of electrostatic screening was also incorporated into the theory of Leibler . This model predicts decreases in the incompatibility between two blocks upon the addition of small amounts of ILs, but experimental observations for a mixture of a diblock copolymer and an IL suggest that the two blocks become significantly immiscible. − Moreover, the volume of ILs is comparable to or even larger than the monomer volumes, but this feature has been largely ignored in existing theories for small inorganic ions. Thus, clarification of the driving force for the phase separation of IL-containing block copolymers is greatly needed and is likely to bridge the gap between theory and experiment.…”

Sub-10 nm Feature Sizes of Disordered Polystyrene-block-poly(methyl methacrylate) Copolymer Films Achieved by Ionic Liquid Additives with Selectively Distributed Charge Interactions

“…In addition, the power law dependence of domain spacing on the composition of BCP/IL blends was used widely. But the power-law index depends irregularly on the selectivity of IL, the morphology of block copolymer, and the compositional block ratio within the same morphology, without clear physical meaning. − …”

“…These authors found that the topology of the phase diagrams of the block copolymer/IL blends and the scaling of the phase-separated domains are significantly influenced by the cation structure of the IL. The balance of Coulombic and van der Waals interactions also influences the topology of the phase diagrams …”

“…The balance of Coulombic and van der Waals interactions also influences the topology of the phase diagrams. 22 In previous studies, Nealey et al developed a procedure to fabricate chemical prepatterns that has been implemented on a 300 mm production line. The tools and process employed in the procedure were industry-friendly.…”

Polarization of ionic liquid and polymer and its implications for polymerized ionic liquids: An overview towards a new theory and simulation

“…All these features that do not exist or are less common in the case of inorganic salts may tarnish the reputation of the existing thermodynamic theories for polymer electrolytes. Among others, the development of the theoretical frameworks and computationally tractable thermodynamic models that consider the microphase separation of IL‐containing block copolymers would be expected to come according to future perspectives regarding smart materials with a mixture of ILs and block copolymers 33 and to surging reports from various experimental groups 10,34–58 …”