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Pei Chen - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and mesomorphic properties of the Nematic Mesophase benzoxazole derivatives with big twist angle of difluoro-biphenyl unit
2018Co-Authors: Qiang Weng, Aiai Gao, Pei Chen, Longyan Duan, Xinbing ChenAbstract:Modifying the position and numbers of lateral fluorine substituent is a common method to design and adjust the Mesophase of liquid crystal compounds. Here, a series of 2-(2,2ʹ-difluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-5-substituted benzoxazole with both non-polar (H, CH3) and polar (NO2) groups (coded as nPF(2)PF(2)Bx) is synthesised and characterised. All of the compounds show a conspicuous inter-ring twist angle of 38° compared with corresponding reference compounds I and II which are calculated by density functional theory method, and it is interesting to note that the final compounds nPF(2)PF(2)Bx show only Nematic Mesophase during heating or cooling. Meanwhile, the UV-vis absorption bands and photoluminescence emission peaks both display remarkable blue-shifted. The aforementioned results reveal that lateral difluoro substituents play a key role to stable the Nematic Mesophase by increasing the dihedral angle of biphenyl.
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synthesis and properties of allyloxy based tolane liquid crystals with high negative dielectric anisotropy
Liquid Crystals, 2017Co-Authors: Ran Chen, Zhongwei An, Xinbing Chen, Liang Zhao, Pei ChenAbstract:ABSTRACTA series of tolane liquid crystals (LCs) containing 2,3-difluorophenyl and allyloxy terminal groups have been synthesised via multi-step reactions. Their thermotropic Mesophases, birefringences and dielectric anisotropy properties are discussed by comparison with the non-fluorinated analog. The results show that the allyloxy-based tolane LC 3TOV reveals a high value of the birefringence (0.29), negative dielectric anisotropy (−4.44) and a broad Nematic Mesophase with a low melting point and high clearing point. The effects of the terminal alkyl chains, the lateral fluoro substituents, the allyloxy terminal group and alkyne bridge on the mesomorphic and physical properties were also discussed. Meanwhile, Density Functional Theory (DFT) calculations of molecular conformation and polarisability were used to correlate the experimental findings.
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improved Nematic Mesophase stability of benzoxazole liquid crystals via modification of inter ring twist angle of biphenyl unit
Liquid Crystals, 2016Co-Authors: Dingqian Shi, Pei Chen, Ran Chen, Aiai Gao, Xinbing ChenAbstract:ABSTRACTA series of Nematic heterocyclic liquid crystals, 2-(2ʹ-fluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(2)PBx) bearing hydrogen (nPF(2)PBH), methyl (nPF(2)PBM) and nitro (nPF(2)PBN) terminal groups, respectively, are developped and investigated. The results show that the Nematic Mesophase stability is obviously improved via a slightly increase in the inter-ring twist angle between the planes of two phenyl rings in the biphenyl unit, where modification of the twist angle can be achieved by adjusting the position of the lateral monofluorine substituent from the outer to the inter ring of the biphenyl mesogenic core unit. Meanwhile, the inter-ring lateral fluorine substituent results in a decrease in both melting and clearing points but only a Nematic Mesophase with an acceptably wide Mesophase range for nPF(2)PBx, and thus a potential application in liquid crystal display mixtures is expected, especially for the compounds nPF(2)PBM and nPF(2)PBN. The reduced π–π interactio...
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Nematic Mesophase enhanced via lateral monofluorine substitution on benzoxazole liquid crystals
Liquid Crystals, 2016Co-Authors: Dingqian Shi, Pei Chen, Ran Chen, Aiai Gao, Xinbing ChenAbstract:ABSTRACTFluorine is widely used as a lateral substituent to modify the physical properties of liquid crystals. Here, laterally monofluorinated compounds, 2-(4ʹ-alkoxy-2-fluorobiphenyl-4-yl)-benzoxazole derivatives (nPPF(2)Bx) bearing different substituents (H, CH3, NO2, coded as nPPF(2)BH, nPPF(2)BM and nPPF(2)BN, respectively) at 5-position, were synthesised and characterised. It is interesting to note that these only display enantiotropic Nematic Mesophases with Mesophase ranges of 12–28°C and 13–45°C on heating and cooling for nPPF(2)BH, 46–97°C and 62–120°C for nPPF(2)BM and 82–108°C and 87–113°C for nPPF(2)BN, which are very different from the corresponding monofluorine-substituted analogue (compounds I) with enantiotropic smectic or smectic/Nematic Mesophases. The enhanced Nematic Mesophase is attributed to the reduced π–π interaction/conjugation resulting from the twisted structure of the molecule caused by the introduction of a fluorine atom into the inter-ring of the biphenyl unit. These results ...
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dielectric and optical anisotropy enhanced by 1 3 dioxolane terminal substitution on tolane liquid crystals
Journal of Materials Chemistry C, 2015Co-Authors: Ran Chen, Zhongwei An, Xinbing Chen, Yi Jiang, Jian Li, Pei ChenAbstract:Four series of 1,3-dioxolane-terminated liquid crystals were prepared via multi-step reactions based on 4-alkylcyclohexanecarboxylic acids. Their structures were confirmed by infrared spectrometry (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS). Their properties were measured by differential scanning calorimetry (DSC), polarising optical microscopy (POM), X-ray diffraction (XRD), Abbe refractometer and an electrical constants instrument. The results show that the positive dielectric anisotropy and birefringence of the tolane-liquid crystals are increased significantly by an introduction of 1,3-dioxolane as a terminal group. The application of the 1,3-dioxolane-terminated liquid crystals in the mixture was investigated and the results show that lower threshold voltage, wider Nematic range and higher birefringence are obtained when compared to the mixture containing liquid crystals with buty-3-enyl as a terminal group. The lateral fluoro substituent, alkyne-bridge and 1,3-dioxolane terminal group enhance the stability of the Nematic Mesophase and the solubility of the corresponding compounds in the common host liquid crystal mixture. Meanwhile, DFT calculations of dipole moments and molecular polarizabilities were used to correlate the experimental findings.
Xinbing Chen - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and mesomorphic properties of the Nematic Mesophase benzoxazole derivatives with big twist angle of difluoro-biphenyl unit
2018Co-Authors: Qiang Weng, Aiai Gao, Pei Chen, Longyan Duan, Xinbing ChenAbstract:Modifying the position and numbers of lateral fluorine substituent is a common method to design and adjust the Mesophase of liquid crystal compounds. Here, a series of 2-(2,2ʹ-difluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-5-substituted benzoxazole with both non-polar (H, CH3) and polar (NO2) groups (coded as nPF(2)PF(2)Bx) is synthesised and characterised. All of the compounds show a conspicuous inter-ring twist angle of 38° compared with corresponding reference compounds I and II which are calculated by density functional theory method, and it is interesting to note that the final compounds nPF(2)PF(2)Bx show only Nematic Mesophase during heating or cooling. Meanwhile, the UV-vis absorption bands and photoluminescence emission peaks both display remarkable blue-shifted. The aforementioned results reveal that lateral difluoro substituents play a key role to stable the Nematic Mesophase by increasing the dihedral angle of biphenyl.
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synthesis and properties of allyloxy based tolane liquid crystals with high negative dielectric anisotropy
Liquid Crystals, 2017Co-Authors: Ran Chen, Zhongwei An, Xinbing Chen, Liang Zhao, Pei ChenAbstract:ABSTRACTA series of tolane liquid crystals (LCs) containing 2,3-difluorophenyl and allyloxy terminal groups have been synthesised via multi-step reactions. Their thermotropic Mesophases, birefringences and dielectric anisotropy properties are discussed by comparison with the non-fluorinated analog. The results show that the allyloxy-based tolane LC 3TOV reveals a high value of the birefringence (0.29), negative dielectric anisotropy (−4.44) and a broad Nematic Mesophase with a low melting point and high clearing point. The effects of the terminal alkyl chains, the lateral fluoro substituents, the allyloxy terminal group and alkyne bridge on the mesomorphic and physical properties were also discussed. Meanwhile, Density Functional Theory (DFT) calculations of molecular conformation and polarisability were used to correlate the experimental findings.
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improved Nematic Mesophase stability of benzoxazole liquid crystals via modification of inter ring twist angle of biphenyl unit
Liquid Crystals, 2016Co-Authors: Dingqian Shi, Pei Chen, Ran Chen, Aiai Gao, Xinbing ChenAbstract:ABSTRACTA series of Nematic heterocyclic liquid crystals, 2-(2ʹ-fluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(2)PBx) bearing hydrogen (nPF(2)PBH), methyl (nPF(2)PBM) and nitro (nPF(2)PBN) terminal groups, respectively, are developped and investigated. The results show that the Nematic Mesophase stability is obviously improved via a slightly increase in the inter-ring twist angle between the planes of two phenyl rings in the biphenyl unit, where modification of the twist angle can be achieved by adjusting the position of the lateral monofluorine substituent from the outer to the inter ring of the biphenyl mesogenic core unit. Meanwhile, the inter-ring lateral fluorine substituent results in a decrease in both melting and clearing points but only a Nematic Mesophase with an acceptably wide Mesophase range for nPF(2)PBx, and thus a potential application in liquid crystal display mixtures is expected, especially for the compounds nPF(2)PBM and nPF(2)PBN. The reduced π–π interactio...
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Nematic Mesophase enhanced via lateral monofluorine substitution on benzoxazole liquid crystals
Liquid Crystals, 2016Co-Authors: Dingqian Shi, Pei Chen, Ran Chen, Aiai Gao, Xinbing ChenAbstract:ABSTRACTFluorine is widely used as a lateral substituent to modify the physical properties of liquid crystals. Here, laterally monofluorinated compounds, 2-(4ʹ-alkoxy-2-fluorobiphenyl-4-yl)-benzoxazole derivatives (nPPF(2)Bx) bearing different substituents (H, CH3, NO2, coded as nPPF(2)BH, nPPF(2)BM and nPPF(2)BN, respectively) at 5-position, were synthesised and characterised. It is interesting to note that these only display enantiotropic Nematic Mesophases with Mesophase ranges of 12–28°C and 13–45°C on heating and cooling for nPPF(2)BH, 46–97°C and 62–120°C for nPPF(2)BM and 82–108°C and 87–113°C for nPPF(2)BN, which are very different from the corresponding monofluorine-substituted analogue (compounds I) with enantiotropic smectic or smectic/Nematic Mesophases. The enhanced Nematic Mesophase is attributed to the reduced π–π interaction/conjugation resulting from the twisted structure of the molecule caused by the introduction of a fluorine atom into the inter-ring of the biphenyl unit. These results ...
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dielectric and optical anisotropy enhanced by 1 3 dioxolane terminal substitution on tolane liquid crystals
Journal of Materials Chemistry C, 2015Co-Authors: Ran Chen, Zhongwei An, Xinbing Chen, Yi Jiang, Jian Li, Pei ChenAbstract:Four series of 1,3-dioxolane-terminated liquid crystals were prepared via multi-step reactions based on 4-alkylcyclohexanecarboxylic acids. Their structures were confirmed by infrared spectrometry (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS). Their properties were measured by differential scanning calorimetry (DSC), polarising optical microscopy (POM), X-ray diffraction (XRD), Abbe refractometer and an electrical constants instrument. The results show that the positive dielectric anisotropy and birefringence of the tolane-liquid crystals are increased significantly by an introduction of 1,3-dioxolane as a terminal group. The application of the 1,3-dioxolane-terminated liquid crystals in the mixture was investigated and the results show that lower threshold voltage, wider Nematic range and higher birefringence are obtained when compared to the mixture containing liquid crystals with buty-3-enyl as a terminal group. The lateral fluoro substituent, alkyne-bridge and 1,3-dioxolane terminal group enhance the stability of the Nematic Mesophase and the solubility of the corresponding compounds in the common host liquid crystal mixture. Meanwhile, DFT calculations of dipole moments and molecular polarizabilities were used to correlate the experimental findings.
Ran Chen - One of the best experts on this subject based on the ideXlab platform.
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synthesis and properties of allyloxy based tolane liquid crystals with high negative dielectric anisotropy
Liquid Crystals, 2017Co-Authors: Ran Chen, Zhongwei An, Xinbing Chen, Liang Zhao, Pei ChenAbstract:ABSTRACTA series of tolane liquid crystals (LCs) containing 2,3-difluorophenyl and allyloxy terminal groups have been synthesised via multi-step reactions. Their thermotropic Mesophases, birefringences and dielectric anisotropy properties are discussed by comparison with the non-fluorinated analog. The results show that the allyloxy-based tolane LC 3TOV reveals a high value of the birefringence (0.29), negative dielectric anisotropy (−4.44) and a broad Nematic Mesophase with a low melting point and high clearing point. The effects of the terminal alkyl chains, the lateral fluoro substituents, the allyloxy terminal group and alkyne bridge on the mesomorphic and physical properties were also discussed. Meanwhile, Density Functional Theory (DFT) calculations of molecular conformation and polarisability were used to correlate the experimental findings.
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improved Nematic Mesophase stability of benzoxazole liquid crystals via modification of inter ring twist angle of biphenyl unit
Liquid Crystals, 2016Co-Authors: Dingqian Shi, Pei Chen, Ran Chen, Aiai Gao, Xinbing ChenAbstract:ABSTRACTA series of Nematic heterocyclic liquid crystals, 2-(2ʹ-fluoro-4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(2)PBx) bearing hydrogen (nPF(2)PBH), methyl (nPF(2)PBM) and nitro (nPF(2)PBN) terminal groups, respectively, are developped and investigated. The results show that the Nematic Mesophase stability is obviously improved via a slightly increase in the inter-ring twist angle between the planes of two phenyl rings in the biphenyl unit, where modification of the twist angle can be achieved by adjusting the position of the lateral monofluorine substituent from the outer to the inter ring of the biphenyl mesogenic core unit. Meanwhile, the inter-ring lateral fluorine substituent results in a decrease in both melting and clearing points but only a Nematic Mesophase with an acceptably wide Mesophase range for nPF(2)PBx, and thus a potential application in liquid crystal display mixtures is expected, especially for the compounds nPF(2)PBM and nPF(2)PBN. The reduced π–π interactio...
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Nematic Mesophase enhanced via lateral monofluorine substitution on benzoxazole liquid crystals
Liquid Crystals, 2016Co-Authors: Dingqian Shi, Pei Chen, Ran Chen, Aiai Gao, Xinbing ChenAbstract:ABSTRACTFluorine is widely used as a lateral substituent to modify the physical properties of liquid crystals. Here, laterally monofluorinated compounds, 2-(4ʹ-alkoxy-2-fluorobiphenyl-4-yl)-benzoxazole derivatives (nPPF(2)Bx) bearing different substituents (H, CH3, NO2, coded as nPPF(2)BH, nPPF(2)BM and nPPF(2)BN, respectively) at 5-position, were synthesised and characterised. It is interesting to note that these only display enantiotropic Nematic Mesophases with Mesophase ranges of 12–28°C and 13–45°C on heating and cooling for nPPF(2)BH, 46–97°C and 62–120°C for nPPF(2)BM and 82–108°C and 87–113°C for nPPF(2)BN, which are very different from the corresponding monofluorine-substituted analogue (compounds I) with enantiotropic smectic or smectic/Nematic Mesophases. The enhanced Nematic Mesophase is attributed to the reduced π–π interaction/conjugation resulting from the twisted structure of the molecule caused by the introduction of a fluorine atom into the inter-ring of the biphenyl unit. These results ...
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dielectric and optical anisotropy enhanced by 1 3 dioxolane terminal substitution on tolane liquid crystals
Journal of Materials Chemistry C, 2015Co-Authors: Ran Chen, Zhongwei An, Xinbing Chen, Yi Jiang, Jian Li, Pei ChenAbstract:Four series of 1,3-dioxolane-terminated liquid crystals were prepared via multi-step reactions based on 4-alkylcyclohexanecarboxylic acids. Their structures were confirmed by infrared spectrometry (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS). Their properties were measured by differential scanning calorimetry (DSC), polarising optical microscopy (POM), X-ray diffraction (XRD), Abbe refractometer and an electrical constants instrument. The results show that the positive dielectric anisotropy and birefringence of the tolane-liquid crystals are increased significantly by an introduction of 1,3-dioxolane as a terminal group. The application of the 1,3-dioxolane-terminated liquid crystals in the mixture was investigated and the results show that lower threshold voltage, wider Nematic range and higher birefringence are obtained when compared to the mixture containing liquid crystals with buty-3-enyl as a terminal group. The lateral fluoro substituent, alkyne-bridge and 1,3-dioxolane terminal group enhance the stability of the Nematic Mesophase and the solubility of the corresponding compounds in the common host liquid crystal mixture. Meanwhile, DFT calculations of dipole moments and molecular polarizabilities were used to correlate the experimental findings.
Orlando J Rojas - One of the best experts on this subject based on the ideXlab platform.
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quantitative calorimetric studies of the chiral Nematic Mesophase in aqueous cellulose nanocrystal suspensions
Langmuir, 2020Co-Authors: Emily G Facchine, Soo Ah Jin, Richard J Spontak, Saad A Khan, Orlando J RojasAbstract:Aqueous suspensions of cellulose nanocrystals (CNCs) can spontaneously form a chiral Nematic Mesophase at a critical concentration (c*). Unfortunately, no current analytical technique permits rapid detection of c*. Herein, we introduce a facile and accurate approach to assess c* rapidly (<2 h) from a small sample volume and compare our results with those obtained by conventional methods. Our strategy employs isothermal titration calorimetry (ITC) to measure the heat associated with interactions in the suspension, which can identify the onset of Mesophase formation as the heat signature is sensitive to the suspension viscosity and thus capable of detecting small changes in the suspension environment. We measure c* for CNC samples differing in surface charge and aspect ratio, and find that both lower aspect ratios and higher surface charges increase c*. Our ITC results reveal the role of CNC interactions prior to the visual observation of Mesophase formation and elucidate mesomorphic effects related to nanocrystals and their suspensions.
A. V. Doshi - One of the best experts on this subject based on the ideXlab platform.
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dependence of molecular structure on mesomorphic behavior with special reference to central bridge
Molecular Crystals and Liquid Crystals, 2015Co-Authors: Brijesh H Patel, Ankita A Doshi, A. V. DoshiAbstract:A novel homologous series of liquid crystalline 4-(4′-n-alkoxy cinnamoyloxy)-4″-methoxy benzyl cinnamates was synthesized and studied with a view to understand and establish the effects of molecular structure on liquid crystal behavior. The series consists of eleven members of the series. None of the homologue derivatives are either nonliquid crystal or smectogenic, i.e. all the eleven members of the novel homologous series are enantiotropcially nematogenic only. Transition and melting temperatures as well as textures of the Nematic Mesophase were determined on an optical polarizing microscope equipped with a heating stage. The transition curves of the phase diagram show phase behavior in a normal expected manner. An odd-even effect is observed for the Nematic-isotropic transition curve. The textures of the Nematic Mesophase are threaded or Schlieren as determined a by miscibility method. Analytical and spectral data confirm the molecular structures of the homologues. The average thermal stability for nem...
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synthesis and mesomorphic properties of a novel ester homologous series 4 4 n alkoxy benzoyloxy benzyl cinnamates
Molecular Crystals and Liquid Crystals, 2015Co-Authors: Brijesh H Patel, A. V. DoshiAbstract:A novel homologous series 4-(4′-n-alkoxy benzoyloxy) benzyl cinnamates was synthesized and studied with a view to understanding and establishing the relationships between mesomorphism and molecular structure. The novel series consists of eleven members with the commencement of mesomorphism from the pentyloxy homologue onwards to the hexadecyl homologue. The remaining homologues are nonmesomorphic. All the mesomorphic homologues exhibit smectogenic mesomorphism in addition to nematogenic mesomorphism for a definite temperature range in an enantiotropic manner, except for the pentyloxy homologue, which exhibits only a nematogenic Mesophase in an enantiotropic manner without the formation of a smectic phase. The texture of the Nematic Mesophase is of the threaded or Schlieren type and the smectic Mesophase is of the type A or C texture, as determined by a miscibility method. Transition temperatures were observed through an optical polarizing microscope equipped with a heating stage. The transition curves of ...
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novel cinnamate esters synthesis and mesomorphic properties in relation to molecular structure
Molecular Crystals and Liquid Crystals, 2014Co-Authors: Brijesh H Patel, A. V. DoshiAbstract:A novel homologous series 4-[4′-n-alkoxy cinnamoyloxy] benzyl cinnamates consisting of 11 homologs was synthesized and studied with a view to understanding and establishing the relation between molecular structure and mesomorphic behavior of a substance. Mesomorphic behavior of the series commences from the third homolog and then continues until the last hexadecyloxy homolog. The first and second members of a series are non-mesomorphic. Nematogenic Mesophase formation is observed from the propoxy homolog to the hexadecyloxy homolog, but the smectogenic Mesophase formation is observed from the hexyloxy homolog to the tetradecyloxy homolog. All mesomorphic transitions are enantiotropic in nature. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. The textures of the Nematic Mesophase are threaded or Schlieren in type and that of the smectic Mesophases are focal conic fan shaped of the smectic A or smectic C type. A phase diagram of the series shows a n...
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synthesis and liquid crystal behavior of a novel ester homologous series
Molecular Crystals and Liquid Crystals, 2014Co-Authors: B. H. Patel, A. V. DoshiAbstract:A novel ester homologous series of 4-[4’-n-alkoxy cinnamoyloxy] benzyl benzoates has been synthesized. The series consists of 12 homologues. Liquid crystal properties commence from the sixth member to the last member of the series with the exhibition of an enantiotropic Nematic phase without the exhibition of any smectogenic Mesophase. The remaining homologues do not exhibit liquid crystal behavior. The texture of the Nematic phase is of the threaded or Schlieren type. The solid-Nematic or isotropic transition curve adopts a zigzag path and the Nematic-isotropic transition curve steeply rises and then falls in the phase diagram and behaves in normal manner. An odd–even effect is absent in the Nematic-isotropic transition curve with an alteration of transition temperatures. The average thermal stability for the Nematic Mesophase is 153.1°C, and the nematogenic temperature ranges vary from 12°C to 50°C. Analytical data confirm the molecular structures of the homologues. The Liquid Crystal properties and tra...
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determination of latent transition temperatures of nonmesomorphs by extrapolation method in binary systems
Molecular Crystals and Liquid Crystals, 2012Co-Authors: A. V. Doshi, U C Bhoya, J J TravadiAbstract:Eight binary systems consisting of mesomorphs and nonmesomorphs (A1 or A2, + B1, B2, … B7, B8) were studied with a view to determine the latent transition temperature (LTT) for the nonmesomorphic component (B) of a binary system by an extrapolation method. Encouraging results supporting earlier views and LTT values were obtained for seven binary systems. Instead of reporting a single value of LTT, the range of temperature or two or three values are reported herewith depending upon the possible paths of extrapolation. LTT reported earlier for nonmesomorphs lie within the range of temperature determined presently. Though the “group slope value” differs from the earlier reported value, the group efficiency order remains the same. Thus, the present investigation raises the credibility of an extrapolation method to determine LTT and group efficiency order for Nematic Mesophase. Component A1 and A2 are nematogenic, namely, p-(p′-n-propyloxy benzoyloxy) anisole (A1) (90.0 to 116.0) and p-(p′-n-butyloxy benzoylox...
