The Design and Investigation of the Self-Assembly of Dimers with two Nematic Phases

TL;DR

This study synthesizes non-symmetric dimers with varied mesogenic groups, investigates their nematic phases using multiple techniques, and proposes models for their self-assembly in the Nx phase.

Contribution

It introduces new non-symmetric dimer molecules, systematically studies their phase behavior, and develops models for their self-assembly mechanisms in nematic phases.

Findings

Identification of two nematic phases in synthesized dimers

Correlation between molecular structure and phase properties

Proposed models for Nx phase self-assembly

Abstract

A series of non-symmetric dimers were synthesised containing either cyanobiphenyl or difluoroterphenyl moieties on one side and a range of long, short, bent, polar or apolar mesogens on the other side of the molecules. The dielectric anisotropy of the mesogens was varied systematically. The systems were characterised by differential scanning calorimetry (DSC), optical polarizing microscopy (OPM) and detailed X-ray diffraction (XRD) studies, both in the nematic and the Nx phase. The results are compared and structure properties relationships are discussed. A model for the assembly in the Nx phase is developed discussing Ntb structures, coaxial helices, swiss roll structures and chiral domain formation.