The Effect of Terminal Alkyl Chain Length on Mesomorphic Properties of 4-Alkoxyphenyl-4'-Alkylbenzoates

Neubert, Mary E.; Carlino, L. T.; Fishel, D. L.; D’Sidocky, Richard

doi:10.1080/00268948008071427

“…Additionally, as shown in Figure 2 and A previous study showed that the liquid crystal compounds can exhibit a systematic oddeven periodic pattern on phase transition properties according to the carbon number in the terminal alkyl chains. [56][57][58][59][60] Through closer examinations, we noticed that the changes in melting points, clearing points, and enthalpies exhibit similar odd-even pattern as shown in Figure 2 and 3.…”

Section: Phases Transition Temperatures and Enthalpies Of Compounds 4a-4gmentioning

confidence: 67%

Synthesis of 4-Chloro-1,3-Diazobenzene Bent-Cores Liquid Crystal and Characterizations of Its Mesogenic Behaviors and Photosensitivity

Lü

¹

,

Zhang

²

,

Yan³

et al. 2021

Preprint

0

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Azobenzene-based bent-core liquid crystals demonstrate a variety of mesomorphic behaviors and photochromic properties which are desirable for optical switching. In this study, a series of novel compounds were synthesized by adding azo functional groups and chlorine substituent to the central bent-cores to form a 4-chloro-1,3-dizaophenylene bent-core. Fouriertransform infrared spectroscopy (FTIR), 1 H and 13 C nuclear magnetic resonance (NMR), mass spectrometry (MS), differential scanning calorimetry (DSC), polarized optical microscopy (POM), and ultraviolet-visible spectroscopy (UV-Vis) were performed to evaluate the structure, mesogenic properties, and photosensitivity of these synthesized compounds. The experimental results show that these compounds exhibit a broad temperature window up to 63.8 °C for nematic phase. In addition, the enhancement of photonic properties of these compounds was exemplified by the high conversion ratio and the rapid rate of trans -cis photoisomerization of compound 4c. The cis fraction of 4c can reach 0.81. At 95 °C, 4c in nematic phase became isotropic liquid under UVirradiation in 3 seconds and can be restored to nematic under natural visible light in 5 seconds. At room temperature, 4c when dissolved in ethyl acetate solution can reach photostationary state in 10 seconds. Quantum mechanics modeling confirms that using azos instead of esters as the central linkages can effectively reduce the molecular dipole moment, which appears to promote favorable mesogenic behaviors and photonic characteristics. Moreover, varying the carbon number in the terminal alkyl chains can alter molecular dipole, especially the polarizability anisotropy, of which the variation is strongly correlated with the phase transition temperature and temperature range of nematic phase. These findings suggest that 1) changing azo group position can effectively alter the molecular dipole; 2) reducing molecular dipole interaction can promote favorable photonic properties of azobenzene bent-core liquid crystal. This study linking the mechanistic details with mesogenic behaviors provides a novel approach to improve the material design for photonic applications.

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“…Additionally, as shown in Figure 2 A previous study showed that the liquid crystal compounds can exhibit a systematic oddeven periodic pattern on phase transition properties according to the carbon number in the terminal alkyl chains. [56][57][58][59][60] Through closer examinations, we noticed that the changes in melting points, clearing points, and enthalpies exhibit similar odd-even pattern as shown in Figure 2 and 3.…”

Section: Phases Transition Temperatures and Enthalpies Of Compounds 4a-4gmentioning

confidence: 67%

Synthesis of 4-Chloro-1,3-Diazobenzene Bent-Cores Liquid Crystal and Characterizations of Its Mesogenic Behaviors and Photosensitivity

Zhang

¹

,

Lü²,

Yan³

et al. 2021

Preprint

0

View full text Add to dashboard Cite

In this study, a series of novel compounds were synthesized by adding azo functional groups and chlorine substituent to the central bent-cores to form a 4-chloro-1,3-dizaophenylene bent-core. The structure, mesogenic properties, and photosensitivity of these synthesized compounds were evaluated experimentally. The results show that these compounds exhibit a broad temperature window up to 63.8 °C for nematic phase and fast <i>trans – cis</i> photoisomerization in seconds with 80% conversion. Quantum mechanics modeling confirms that using azos as the central linkages can effectively reduce the molecular dipole moment, which appears to promote favorable mesogenic behaviors and photonic characteristics. Moreover, varying the carbon number in the terminal alkyl chains can alter molecular dipole, especially the polarizability anisotropy, of which the variation is strongly correlated with the phase transition temperature and temperature range of nematic phase. These findings suggest that reducing molecular dipole can promote favorable mesogenic and photonic properties.

show abstract

“…Additionally, as shown in Figure 2 A previous study showed that the liquid crystal compounds can exhibit a systematic oddeven periodic pattern on phase transition properties according to the carbon number in the terminal alkyl chains. [57][58][59][60][61] Through closer examinations, we noticed that the changes in melting points, clearing points, and enthalpies exhibit similar odd-even pattern as shown in Figure 2 and 3.…”

Section: Phases Transition Temperatures and Enthalpies Of Compounds 4a-4gmentioning

confidence: 67%

Synthesis, Characterization, and Effects of Molecular Structure on Phase Behavior of 4-Chloro-1,3-Diazobenzene Bent-Core Liquid Crystals with High Photosensitivity

Lü

¹

,

Yan

²

,

Zhang

³

et al. 2021

Preprint

0

View full text Add to dashboard Cite

In this study, a series of novel compounds were synthesized by adding azo functional groups and chlorine substituent to the central bent-cores to form a 4-chloro-1,3-dizaophenylene bent-core. The structure, mesogenic properties, and photosensitivity of these synthesized compounds were evaluated experimentally. The results show that these compounds exhibit a broad temperature window up to 63.8 °C for nematic phase and fast <i>trans – cis</i> photoisomerization in seconds with 80% conversion. Quantum mechanics modeling confirms that using azos as the central linkages can effectively reduce the molecular dipole moment, which appears to promote favorable mesogenic behaviors and photonic characteristics. Moreover, varying the carbon number in the terminal alkyl chains can alter molecular dipole, especially the polarizability anisotropy, of which the variation is strongly correlated with the phase transition temperature and temperature range of nematic phase. These findings suggest that reducing molecular dipole can promote favorable mesogenic and photonic properties.

show abstract

The Effect of Terminal Alkyl Chain Length on Mesomorphic Properties of 4-Alkoxyphenyl-4'-Alkylbenzoates

Cited by 38 publications

References 9 publications

Synthesis of 4-Chloro-1,3-Diazobenzene Bent-Cores Liquid Crystal and Characterizations of Its Mesogenic Behaviors and Photosensitivity

Synthesis of 4-Chloro-1,3-Diazobenzene Bent-Cores Liquid Crystal and Characterizations of Its Mesogenic Behaviors and Photosensitivity

Synthesis of 4-Chloro-1,3-Diazobenzene Bent-Cores Liquid Crystal and Characterizations of Its Mesogenic Behaviors and Photosensitivity

Synthesis, Characterization, and Effects of Molecular Structure on Phase Behavior of 4-Chloro-1,3-Diazobenzene Bent-Core Liquid Crystals with High Photosensitivity

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