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Helical networks of π‐conjugated rods – A robust design concept for bicontinuous cubic liquid crystalline phases with achiral Ia 3⎯⎯3¯d and chiral I23 lattice

DOI: 10.1002/adfm.202004353 DOI Help

Authors: Christian Dressel (Martin Luther University Halle‐Wittenberg) , Tino Reppe (Martin Luther University Halle‐Wittenberg) , Silvio Poppe (Martin Luther University Halle‐Wittenberg) , Marko Prehm (Martin Luther University Halle‐Wittenberg) , Huanjun Lu (University of Sheffield) , Xiangbing Zeng (University of Sheffield) , Goran Ungar (University of Sheffield; Xi'an Jiaotong University) , Carsten Tschierske (Martin Luther University Halle‐Wittenberg)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Functional Materials , VOL 23

State: Published (Approved)
Published: August 2020

Open Access Open Access

Abstract: Bicontinuous cubic liquid crystalline phases of π‐conjugated molecules, representing self‐assembled 3D‐ordered interpenetrating networks with cubic symmetry, are receiving increasing attention due to their capacity for charge transport in all three dimensions and their inherent spontaneous helicity. Herein, a robust general design concept for creating bicontinuous cubic phases is reported. It is based on a nonsymmetric‐substituted π‐conjugated 5,5′‐diphenyl‐2,2′‐bithiophene platform with one end containing three out‐fanning flexible chains and with a range of substituents at the other end (the apex). The cubic phases are stable over broad temperature ranges, often down to ambient temperature, and tolerate a wide range of apex substitution patterns, allowing structural diversity and tailoring of the cubic phase type and application‐relevant properties. With an increasing number and size of apex substituents, a sequence of three different modes of cubic self‐assembly is observed, following an increasing helical twist. Thus, two ranges of the achiral double network Ia 3⎯⎯ 3 ¯ d phase range can be distinguished, a long pitch and a short pitch, with the chiral triple network I23 cubic phase in the intermediate pitch range. The findings provide a new prospect for the directed design of cubic phase‐forming functional materials based on spontaneously formed helical network liquid crystals with tunable application specific properties.

Journal Keywords: bicontinuous cubic phases; chirality; helical superstructures; liquid crystals; mirror symmetry breaking; self‐assembly; supramolecular networks

Subject Areas: Materials, Chemistry

Instruments: I22-Small angle scattering & Diffraction

Other Facilities: B28 at ESRF