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

Johanna MajoinenCécile BouilhacPatrice RannouRedouane Borsali
Published in: ACS macro letters (2022)
We designed and synthesized high χ-low N -maltoheptaose-(triazolium + /N(SO 2 CF 3 ) 2 - )-polyisoprene-(triazolium + /N(SO 2 CF 3 ) 2 - )-maltoheptaose ABA triblock elastomers featuring triazolium + /N(SO 2 CF 3 ) 2 - (TFSI - ) counteranion ionic interfaces separating their constituting polymeric sub-blocks. Spin-coated and solvent-vapor-annealed (SVA) MH 1.2k -(T + /TFSI - )-PI 4.3k -(T + /TFSI - )-MH 1.2k 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 MH 1.2k -(T + /TFSI - )-PI 4.3k -(T + /TFSI - )-MH 1.2k and pristine triBCP analogous thin films revealed sub-10 nm block copolymer (BCP) self-assembly and unidirectionally aligned nanostructures developed over several μm 2 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.
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