Configuration effects of H-bonded sites and rigid core lengths on H-bonded banana-shaped liquid crystalline supramolecules consisting of symmetric trimers and asymmetric heterodimers

Ling Yung Wang, I. Hung Chiang, Po Jen Yang, Wan Sheung Li, I. To Chao, Hong-Cheu Lin*

*Corresponding author for this work

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

Several series of novel banana-shaped H-bonded symmetric trimers (with two H-bonds) and asymmetric heterodimers (with one H-bond) were self-assembled by appropriate molar ratios of proton donors (H-donors) and acceptors (H-acceptors). The influences of H-bonded linking positions and aromatic ring numbers (4-8 aromatic rings in the rigid cores) as well as the chain lengths (n, m ) 12 or 16, respectively, in the flexible parts) on the mesomorphism and the switching behavior of the bent-core supramolecules were evaluated and theoretically analyzed. Except for the supramolecular structures with longer rigid cores or shorter flexible chains possessing the rectangular columnar (Colr or B1) phase, the SmCAPA phase was revealed in most supramolecular asymmetric heterodimers and switched to the SmCSPF phase by applying electric fields. The polar smectic C phase was dominated for those with H-bonded sites apart from the core center. Interestingly, the SmA and nematic phases were observed in H-bonded asymmetric dimers with H-bonded sites close to the core center, which theoretically proved that the polar smectic C phase was disfavored due to an unfavorable bend angle (smaller than the lower limit of 110°) in the lowest-energy H-bonded conformer. Compared with the fully covalently bonded analogue, lower transition temperatures and lower threshold voltages were developed in the H-bonded asymmetric dimers with the polar smectic C phase. On the basis of the theoretical calculations of molecular modeling, the existence of polar switching behavior in the polar smectic C phase of asymmetric heterodimers was proven to be associated with their configurations with higher dipole moments and suitable bend angles. Furthermore, the lack of polar switching behavior in supramolecular symmetric trimers, which exhibited the regular SmC phase with weak electrical stabilities, was related to their configurations with smaller dipole moments and confirmed by theoretical calculations.

Original languageEnglish
Pages (from-to)14648-14660
Number of pages13
JournalJournal of Physical Chemistry B
Volume113
Issue number44
DOIs
StatePublished - 11 May 2009

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