An FT-IR spectroscopic study of the role of hydrogen bonding in the formation of liquid crystallinity for mixtures containing bipyridines and 4-pentoxybenzoic acid

Martínez‐Felipe, Alfonso; Cook, A.G.; Abberley, Jordan P.; Walker, Rebecca; Storey, John M. D.; Imrie, Corrie T.

doi:10.1039/c6ra17819g

Cited by 92 publications

(62 citation statements)

References 62 publications

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“…Consequently, TEMPO-oxidized CNFs and NCC might have strong intra-molecular hydrogen bonds within the polymeric chain network. ( Ching, Rahman, Ching, Sukiman, Cheng, 2015;Martinez-Felipe et al, 2016;Salas, Nypelö, Rodriguez-Abreu, Carrillo, & Rojas, 2014).…”

Section: Effect Of Rapid Cooling On Structural Property Of the Nanocementioning

confidence: 99%

Effect of TEMPO-oxidization and rapid cooling on thermo-structural properties of nanocellulose

Haniffa

Ching

Chuah

et al. 2017

Carbohydrate Polymers

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Recently, surface functionality and thermal property of the green nanomaterials have received wide attention in numerous applications. In this study, microcrystalline cellulose (MCC) was used to prepare the nanocrystalline celluloses (NCCs) using acid hydrolysis method. The NCCs was treated with TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxy radical]-oxidation to prepare TEMPO-oxidized NCCs. Cellulose nanofibrils (CNFs) also prepared from MCC using TEMPO-oxidation. The effects of rapid cooling and chemical treatments on the thermo-structural property studies of the prepared nanocelluloses were investigated through FTIR, thermogravimetric analysis-derivative thermogravimetric (TGA-DTG), and XRD. A posteriori knowledge of the FTIR and TGA-DTG analysis revealed that the rapid cooling treatment enhanced the hydrogen bond energy and thermal stability of the TEMPO-oxidized NCC compared to other nanocelluloses. XRD analysis exhibits the effect of rapid cooling on pseudo 2 helical conformation. This was the first investigation performed on the effect of rapid cooling on structural properties of the nanocellulose.

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Section: Effect Of Rapid Cooling On Structural Property Of the Nanocementioning

confidence: 99%

Effect of TEMPO-oxidization and rapid cooling on thermo-structural properties of nanocellulose

Haniffa

Ching

Chuah

et al. 2017

Carbohydrate Polymers

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“…For the C=O group of the dipyridine, the formation of the complex has an intensive effect on the stretching vibration of the C=O group of the ester linkage of the dipyridine part; its wave number increases by 16 cm −1 from 1727 to 1743 cm −1 . For Fermi resonance vibration bands, it has been reported [22,[58][59][60][61][62][63] that they are an important evidence on the H-bond formation. There are three Fermi bands of the H-bonded OH groups, A-, B-, and C-types.…”

Section: Ft-ir Conformation Of Prepared Smhblcsmentioning

confidence: 99%

New Symmetrical U- and Wavy-Shaped Supramolecular H-Bonded Systems; Geometrical and Mesomorphic Approaches

et al. 2020

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New mesomorphic symmetrical 2:1 supramolecular H-bonded complexes of seven phenyl rings were prepared between 4-n-alkoxyphenylazobenzoic acids and 4-(2-(pyridin-3-yl)diazenyl)phenyl nicotinate. Mesomorphic studies of the prepared complexes were investigated using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands of the formed H-bonded interactions were confirmed by FT-IR spectroscopy. Geometrical parameters for all complexes were performed using the density functional theory (DFT) calculations method. Theoretical results revealed that the prepared H-bonded complexes are in non-linear geometry with U-shaped and wavy-shaped geometrical structures; however, the greater linearity of the wavy-shaped compounds could be the reason for their stability with respect to the U-shaped conformer. Moreover, the stable, wavy shape of supramolecular H-bonded complexes (SMHBCs) has been used to illustrate mesomeric behavior in terms of the molecular interaction. The experimental mesomorphic investigations revealed that all complexes possess enantiotropic smectic C phase. Phases were confirmed by miscibility with a standard smectic C (SmC) compound. A comparison was constructed to investigate the effect of incorporating azophenyl moiety into the mesomeric behavior of the corresponding five-membered complexes. It was found that the addition of the extra phenylazo group to the acid moiety has a great increment of the mesophase stability (TC) values with respect to the monotropic SmC phase of the five aromatic systems to the high stable enantiotropic SmC mesophase.

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“…Moreover, it has been reported [65][66][67][68][69][70][71] that the main evidence of the H-bond formation SMC is the presence of three Fermi resonance of OH group: A-, B-, and C-types. The A-type Fermi band presented at 2917.9 to 2853.3 cm −1 under the C-H peaks.…”

Section: Ft-ir Conformationmentioning

confidence: 99%

Chair- and V-Shaped of H-bonded Supramolecular Complexes of Azophenyl Nicotinate Derivatives; Mesomorphic and DFT Molecular Geometry Aspects

et al. 2020

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New geometrical architectures of chair- and V-shaped supramolecular liquid crystalline complexes were molded through 1:1 intermolecular hydrogen bonding interactions between 4-(4-(hexyloxy)phenylazo)methyl)phenyl nicotinate and 4-alkoxybenzoic acids. The length of terminal alkoxy acid chains varied, n = 6 to 16 carbons. The mesomorphic behaviour of these complexes was examined through differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fourier-transform infrared spectroscopy (FT-IR) was carried out to confirm the presence of Fermi bands that appeared for the hydrogen bonding formation. Enantiotropic nematic phases were observed and covered all lengths of alkoxy chains. The geometrical structures of the prepared supramolecular complexes geometries were estimated by Density functional theory (DFT) calculations. The supramolecular complexes I/An are projected to exhibit a nonlinear geometry with V-shaped and chair-shaped geometry. The chair-shaped conformers of I/An were found to be more stable than V-shaped isomeric complexes. Moreover, the effect of the change of the mesogenic core on the mesophase thermal stability (TC) has been investigated by a comparative study of the present azo supramolecular H-bonding LCs (SMHBCs) I/An and our previously reported their Schiff base analogue complexes, II/An. The findings of the DFT illustrated the high impact of CH=N as a mesogenic core on the mesomorphic behavior in terms of the competitive lateral and terminal intermolecular interactions as well as the molecular electrostatic potential (MEP).

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An FT-IR spectroscopic study of the role of hydrogen bonding in the formation of liquid crystallinity for mixtures containing bipyridines and 4-pentoxybenzoic acid

Abstract: The relationships between liquid crystallinity and hydrogen bonding are studied in mixtures containing 4-pentoxybenzoic acid, 5OBA, and five bipyridines, XBiPy, with spacers having different flexibilities, by Fourier transform infrared spectroscopy.

Cited by 92 publications

References 62 publications

Effect of TEMPO-oxidization and rapid cooling on thermo-structural properties of nanocellulose

Effect of TEMPO-oxidization and rapid cooling on thermo-structural properties of nanocellulose

New Symmetrical U- and Wavy-Shaped Supramolecular H-Bonded Systems; Geometrical and Mesomorphic Approaches

Chair- and V-Shaped of H-bonded Supramolecular Complexes of Azophenyl Nicotinate Derivatives; Mesomorphic and DFT Molecular Geometry Aspects

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