Induced Smectic-G Phase through Intermolecular Hydrogen Bonding, Part XII: Thermal and Phase Behaviour of p-aminobenzonitrile: p-n-alkoxybenzoic acids

Abstract

IntroductionSupramolecular liquid crystals, obtained through hydrogen-bonding of complementary molecules, have extensively been investigated in recent years. Following the well-established examples of liquid crystal formation through dimerization of aromatic carboxylic acids [1,2], several classes of compounds have been reported, including conventional liquid crystals [3][4][5][6][7][8][9], supramolecular polymer networks [10][11][12][13], and ferroelectric liquid crystals [14][15][16][17] formed by the interaction of complementary molecules, the liquid crystalline behaviour of which is crucially dependent on the structure of the resulting supramolecular system. It is now well-established that for the formation of liquid crystalline materials through hydrogen bonding, the complementarity of the interacting components coupled with the directionality of the hydrogen bonds are the main (but not the only) factors contributing to liquid crystallinity [18]. In fact, it has been widely accepted that the proton donor and acceptor capabilities of the atoms of the functional groups involved in the hydrogen bonding contribute remarkably to the occurrence of new phases and their thermal stability. Despite their low bond activation energies, these non-covalent interactions show a profound impact on thermal and physical properties such as melting points, heats of vaporization, mesomorphic behaviour, etc.In continuation of our systematic investigation of Hbonded liquid crystals comprising different proton and acceptor groups [19][20][21][22][23], the present communication deals with the synthesis and phase behaviour of a new series of liquid crystalline systems involving intermolecular hydrogen bonding between p-n-alkoxybenzoic acids (nABA) and p-aminobenzonitrile (ABN). The molecular structure of the ABN:nABA series is represented in Figure 1. New liquid crystalline compounds involving intermolecular hydrogen bonding between mesogenic p-n-alkoxybenzoic acids (nABA) (where n denotes the alkoxy carbon number varying from propylto decyl-and dodecyl-) and p-aminobenzonitrile (ABN) are synthesized. The thermal and phase behaviour of these materials is studied by Thermal Microscopy and Differential Scanning Calorimetry. A detailed IR spectral investigation in solid and solution states confirms the formation of H-bonding between cyano and -COOH groups of ABN and nABA, respectively. Comparative thermal analyses of both free p-n alkoxybenzoic acids and H-bonded complexes suggest the induction of smectic-G phase in all the complexes.

Induced crystal G phase of liquid crystalline amide through inter molecular hydrogen bonding

“…2 shrinking the nematic phase from its isotropic state. The natural layered texture of crystal G phase [13][14][15][16][17] indicates the ordered crystalline nature. In the higher members of complexes 6-10 and 12 exhibit nematic droplets and transformed 1393 3370 3168 771 3 1672 1410 3367 3166 2956 687 4 1671 1399 3376 3167 2964 688 5 1674 1423 3371 3165 2948 692 6 1672 1398 3371 3167 2941 688 7 1669 1394 3371 3167 2935 687 8 1675 1402 3371 3167 2935 688 9 1672 1401 3373 3165 2928 697 10 1671 1398 3375 3169 2925 687 12 1672 1399 3372 3172 2924 687 Table 2 Thermal behavior of free p-n-alkoxy benzoic acids (nAOBA).…”

“…The formation of these hydrogen bonds played crucial role in self assembling process and building organized molecular structures [5,6]. In previous studies many liquid crystalline materials were synthesized with either mesomorphic or non-mesomorphic [7][8][9][10] compounds cross linked by non-covalent interactions [11,12] and with inducement of phases [13][14][15][16][17] attracted more interest that hold promise in potential applications [9] leading to supramolecular structures [18] due to its stability and directionality [19]. With untiring efforts and quest in the development, new liquid crystals are attributed between the p-n-alkoxy benzoic acids and cinnamamide.…”

Influence of hydrogen bonding on phase abundance in ferroelectric liquid crystals

“…Although the first reports of H-bonding in LCs date back to the 1960s [3,4], much research took place in the last two decades of the twentieth century [5][6][7][8][9][10][11][12][13][18][19][20][21][22]. It was noticed that their lower bonding and activation energies showed a profound influence on their thermal properties, viz.…”

Induced Smectic A Phase through Intermolecular Hydrogen Bonding: Part XVIII: Influence of p-n-Alkyl Benzoic Acids on Thermal and Phase Behavior οf Hydrogen-Bonded Liquid Crystals

“…The role of H-bonding interactions in the formation and/or stabilization of liquid crystalline phases has also been recognized [6]. Novel series of liquid crystalline materials involving interactions of intermolecular H-bonding between mesogens [7], mesogens and non-mesogens [8,9] and non-mesogens [10] have been synthesized. In determining the structural packing, properties of molecular assemblies [11] and the variation of mesogenic behavior of molecules [12], these non-covalent H-bonding interactions between functional groups play a critical role [13].…”