Synthesis and Characterization of Supramolecular Hydrogen-Bonded Liquid Crystals Comprising of p-n-Alkyloxy Benzoic Acids with Suberic Acid and Pimelic Acid

Subhapriya, P.; Vijayanand, P. S.; Mohan, M. L. N. Madhu

doi:10.1080/15421406.2012.741338

Cited by 21 publications

(6 citation statements)

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“…To provide insight into the molecular interactions underlying the formation of heterodimers of C4BA/C5CA (50/50 mol%), we performed IR spectroscopy ( Figure 3 a) to characterize the C=O stretching vibration (see Table 1 for a summary of the peak assignments). Past studies have established that the C=O vibrations are distinct for dimeric and monomeric carboxylic acid groups [ 22 ]. As shown in Figure 3 a, we first measured the IR spectra of pure C5CA and C4BA, revealing C=O peaks at 1693 and 1680 cm −1 , respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Our design of a LC phase formed through hydrogen bonding was guided by past reports [ 21 , 22 ] that benzoic acids dimerize through intermolecular hydrogen bonding, leading to the formation of supramolecular mesogenic species that form LC phases [ 21 , 22 , 23 ]. In addition, a range of benzoic acid derivatives have been explored, including mixtures with pyridyl or aliphatic groups, and many were shown to form hydrogen bonding LCs through dimerization [ 24 , 25 , 26 , 27 ].…”

Section: Introductionmentioning

confidence: 99%

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Design of Chemoresponsive Soft Matter Using Hydrogen-Bonded Liquid Crystals

Wang

Szilvási

et al. 2021

Materials

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Soft matter that undergoes programmed macroscopic responses to molecular analytes has potential utility in a range of health and safety-related contexts. In this study, we report the design of a nematic liquid crystal (LC) composition that forms through dimerization of carboxylic acids and responds to the presence of vapors of organoamines by undergoing a visually distinct phase transition to an isotropic phase. Specifically, we screened mixtures of two carboxylic acids, 4-butylbenzoic acid and trans-4-pentylcyclohexanecarboxylic acid, and found select compositions that exhibited a nematic phase from 30.6 to 111.7 °C during heating and 110.6 to 3.1 °C during cooling. The metastable nematic phase formed at ambient temperatures was found to be long-lived (>5 days), thus enabling the use of the LC as a chemoresponsive optical material. By comparing experimental infrared (IR) spectra of the LC phase with vibrational frequencies calculated using density functional theory (DFT), we show that it is possible to distinguish between the presence of monomers, homodimers and heterodimers in the mixture, leading us to conclude that a one-to-one heterodimer is the dominant species within this LC composition. Further support for this conclusion is obtained by using differential scanning calorimetry. Exposure of the LC to 12 ppm triethylamine (TEA) triggers a phase transition to an isotropic phase, which we show by IR spectroscopy to be driven by an acid-base reaction, leading to the formation of ammonium carboxylate salts. We characterized the dynamics of the phase transition and found that it proceeds via a characteristic spatiotemporal pathway involving the nucleation, growth, and coalescence of isotropic domains, thus amplifying the atomic-scale acid-base reaction into an information-rich optical output. In contrast to TEA, we determined via both experiment and computation that neither hydrogen bonding donor or acceptor molecules, such as water, dimethyl methylphosphonate, ethylene oxide or formaldehyde, disrupt the heterodimers formed in the LC, hinting that the phase transition (including spatial-temporal characteristics of the pathway) induced in this class of hydrogen bonded LC may offer the basis of a facile and chemically selective way of reporting the presence of volatile amines. This proposal is supported by exploratory experiments in which we show that it is possible to trigger a phase transition in the LC by exposure to volatile amines emitted from rotting fish. Overall, these results provide new principles for the design of chemoresponsive soft matter based on hydrogen bonded LCs that may find use as the basis of low-cost visual indicators of chemical environments.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Design of Chemoresponsive Soft Matter Using Hydrogen-Bonded Liquid Crystals

Wang

Szilvási

et al. 2021

Materials

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“…Earlier studies reported that increasing the terminal alkyl group gives rise to supramolecular hydrogen-bonded complexes with 4-alkoxybenzoic acid liquid crystal which has lower melting point, greater mesophase and thermal stability. Additionally, alkyl chain length is a very important parameter which influences the properties of mesogen molecules [19,20]. Depending on the detailed literature investigation of alkoxybenzoic acid and 4-alkoxybenzoic acid liquid crystals, it seems that most of the studies are focused on liquid crystal properties and crystal structure [21][22][23][24][25]15], and thermodynamic and spectroscopic properties [26][27][28][29][30][31]17,18].…”

Section: Introductionmentioning

confidence: 99%

Solvatochromic fluorescence of 4-alkoxybenzoic acid liquid crystals: Ground and excited state dipole moments of monomer and dimer structures determined by solvatochromic shift methods

Sıdır

2015

Journal of Molecular Liquids

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“…Мезо-генные димеры -самая простая архитектурная форма супрамолекулярных жидких кристаллов, они наиболее распространены и изучены [8,9]. Однако наиболее многочисленными являются суп-рамолекулярные мезогены, формирование которых происходит за счет процессов межмолекулярного узнавания соединений различного строения.…”

Section: Introductionunclassified