Unidirectional Perpendicularly Aligned Lamella-Structured Oligosaccharide (A) ABA Triblock Elastomer (B) Thin Films Utilizing Triazolium⁺/TFSI⁻Ionic Nanochannels

We designed and synthesized high χ-low N-maltoheptaose-(triazolium⁺/N(SO2CF3)2⁻)-polyisoprene-(triazolium⁺/N-(SO2CF3)2⁻)-maltoheptaose ABA triblock elastomers featuring triazolium⁺/N(SO2CF3)2⁻(TFSI⁻) counteranion ionic interfaces separating their constituting polymeric sub-blocks. Spin-coated and solvent-vapor-annealed (SVA) MH1.2k-(T⁺/TFSI⁻)-PI4.3k-(T⁺/TFSI⁻)-MH1.2k thin films demonstrate interface-induced charge cohesion through ca. 1 nm “thick” ionic nanochannels which facilitate the self-assembly of a perpendicularly aligned lamellar structure. Atomic force microscopy
(AFM) and (grazing-incidence) small-angle X-ray scattering ((GI)-SAXS) characterizations of MH1.2k-(T⁺/TFSI⁻)-PI4.3k-(T⁺/TFSI⁻)-MH1.2k and pristine triBCP analogous thin films revealed sub-10 nm block copolymer (BCP) self-assembly and unidirectionally aligned nanostructures developed over several μm2 areas. Solvated TFSI⁻ counterions enhance the oligosaccharide sub-block packing during SVA. The overall BCP phase behavior was mapped through SAXS characterizations comparing di- vs triblock polymeric architectures, a middle PI sub-block with two different molecular masses, and TFSI⁻or I⁻ counteranion effects. This work highlights the benefits of inducing single-point electrostatic interactions within chemical structures of block copolymers to master the long-range self-assembly of prescribed morphologies.