Preliminary communication - Miscibility of a hydrogen-bonded mesogenic complex with normal liquid crystals

Abstract

Recently, there has been increasing interest in the use liquid crystals for miscibility study. The molecular strucof hydrogen bonding between di erent molecular species tures of these materials are given in ® gure 1. Complex for building new liquid crystals [1± 3]. A variety of low 6O BA /8Py shows a nematic phase from 50 to 31ß C on molar mass liquid crystals [ 4± 7 ], polymeric liquid cooling; a nematic phase is seen for 4-hexyloxybenzoic crystals [8,9 ], and mesogenic networks [10] have acid ( 6O BA ) from 151 to 95ß C on cooling, while been built through intermolecular hydrogen bonds.4-octylpyridine ( 8Py) is an isotropic liquid at room Furthermore, the applicability of hydrogen-bonded temperature and exhibits no mesomorphic behaviour. liquid crystals for electro-optic devices has been studied Upon cooling, compound OPH OB exhibits isotropic± for both smectogenic and nematogenic complexes nematic, nematic± smectic A, and smectic A± crystal [11± 17]. The induction of chiral smectic C phases and transitions at 59, 39, and 11ß C, respectively; compound ferroelectric properties have also been observed for 7C B displays a nematic phase from 40 to 2ß C. hydrogen-bonded complexes derived from chiral molecu-The binary phase diagram for mixtures of 6O BA /8Py lar components [11± 14 ]. Moreover, room-temperature and OPH OB is shown in ® gure 2. The phase transition nematic phases can be achieved for complexes of benzoic behaviour was observed visually on cooling. Complex acid derivatives and simple 4-alkylpyridines [15± 17], 6O BA /8Py is miscible with OPH OB and no phase and alignment on rubbed surfaces and electro-optic separation is observed. The mixtures of these two nemae ects in a twisted nematic cell have been observed for togenic materials exhibit nematic phases over the entire the room temperature nematics [ 16]. range of composition; the I± N transition temperature The applicability of hydrogen-bonded liquid crystals behaviour is almost linear. may be widened if these materials can be used in It is known that in an ideal system the clearing point mixtures with normal liquid crystals that are used for display devices. In the present communication, we report liquid crystalline properties for binary mixtures of a hydrogen-bonded mesogenic complex with normal liquid crystal materials which involve only covalent bonds.We selected a 1 5 1 complex ( 6O BA /8Py) [ 15, 16] consisting of 4-hexyloxybenzoic acid and 4-octylpyridine as a hydrogen-bonded mesogenic complex, and 4-octylphenyl 4-hexyloxybenzoate (OPHOB ) [ 16,18] and 4¾ -heptyl-4-cyanobiphenyl ( 7C B) [19] as normal Figure 1. Structures of the hydrogen-bonded liquid crystal complex and normal liquid crystal materials used in this study.

Synthesis of urea‐containing ABA triblock copolymers: Influence of pendant hydrogen bonding on morphology and thermomechanical properties

“…A commonly utilized noncovalent interaction is hydrogen bonding due to its potential for specificity, directionality, and reversibility. Thus, researchers invoke thermo‐reversible hydrogen bonding as a means to improve mechanical properties, induce microphase separation, impart self‐healing performance, and facilitate liquid crystal formation …”

Self-Assembly of Liquid-Crystalline Polyamide Complexes through the Formation of Double Hydrogen Bonds between a 2,6-Bis(amino)pyridine Moiety and Benzoic Acids

“…Hydrogen bonding has been shown to be useful for the development of liquid-crystalline polymer blends because miscibility and structures can be controlled by the interactions between different polymeric components . A variety of low molecular weight complexes have also been obtained by hydrogen bonds between different − or identical molecules.

1 Schematic illustration of supramolecular liquid-crystalline complexes.

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Hydrogen Bonding for Supramolecular Liquid Crystals

“…Hydrogen bonded rodlike complexes 1, 6, 7, 8 are nematic mesogens. Mesogenic complex 6 composing with only two aromatic rings shows room temperature twisted nematic mesophases (TN) [32][33][34][35][36] with electro-optical response. Complex 1 [18] with longer aromatic cores exhibits a mesophase up to 252°C.…”