Yu Cao*^ab, Tejal Nirgude^c, Frédéric Dubois^d, Dharmendra Pratap Singh*^d, Fengcheng Xi^a, Feng Liua^b, Mohamed Alaasar*^ce. J. Mater. Chem. C, 2026,14, 1799-1804

π-conjugated liquid crystals, due to their unique combination of order and mobility, have emerged as versatile platforms for applications such as electronics and photonics. The incorporation of specific functional groups and structural units into liquid crystals can significantly modulate their self-assembly behavior and physical properties. Introducing a bent shape into the conjugated core represents an efficient approach to create novel assembly structures. The bent-core strategy is also closely linked to polarity and ferroelectricity, making it a crucial topic in functional liquid crystals. However, a clear paradigm for controlling the physical properties of bent-core liquid crystal molecules remains elusive, and elucidating their structure-property relationships is a key approach for such liquid crystal materials.

Figure 1. Two typical self-assembled structures of the novel bent-core liquid crystal molecules and their SCLC results

In this work, we designed bent-core molecules based on a 4-bromoresorcinol core. By introducing a bromine substituent at the apex of the bent-core structure and fluorinating the aromatic core at different positions (AHH, AFH, AFF), we modulated the open angle, packing mode, and conductive properties of the molecules. Fluorination at specific sites on the conjugated core enabled us to systematically tune the arrangement between conjugated cores through both the steric effect (weakening conjugation) and the electron-withdrawing effect (strengthening conjugation) of the fluorines. As shown in Figure 1a-b, the peripherally fluorinated molecule AFH, induced by steric effects, adopts a novel assembly mode for bent-core molecules. This mode combines both columnar phases and micellar structures, representing a new type of assembly intermediate between columnar and micellar phases. In contrast, the non-fluorinated and fully fluorinated molecules AHH and AFF form conventional hexagonal columnar structures (Figure 1d-e), indicating the significant role of core fluorination in modulating the assembly structure. This change in assembly mode is directly reflected in the functional properties of the materials. The influence of fluorination on hole mobility was determined using the space-charge-limited current (SCLC) technique. AFH exhibited the lowest hole mobility, 2.48x10^-5 cm²V^-1s^-1, as shown in Figure 1c, due to limited hole transport pathways within its three-dimensional structure. In contrast, AHH, benefiting from conjugation effects and one-dimensional channels within the columnar phase, showed a more than 1000 times boosting at most in Figure 1f, reaching mobilities as high as 2.68Í10^-2 cm²V^-1s^-1 and 2.65Í10^-3 cm²V^-1s^-1.

In summary, this work constitutes a modulation strategy based on conjugated core fluorination for the functionalization of bent-core molecules and the expansion of phase behavior in liquid crystal systems. Besides, the work enables a significant enhancement in hole mobility. This exhibits broad application prospects in fields such as flexible electronics, organic field-effect transistors, and photodetectors.

First Author: Assoc. Prof. Cao Yu, Xi’an Jiaotong University

Correspondence Authors: Assoc. Prof. Cao Yu; Assoc. Prof. Dharmendra Pratap Singh, Universite’ du Littoral Cote d’Opale; Assoc. Prof. Mohamed Alaasar, Cairo University

Full Text Link: https://doi.org/10.1039/D5TC03932K