Polymorphisme d'un Composé Nématique Dérivé de' I'Acide Cinnamique

Hochapfel, A.; Berchet, D.; Perron, Roger; Petit, J

doi:10.1080/15421407108084961

Cited by 7 publications

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References 5 publications

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“…carried out on an adiabatic calorimeter [8] in the Such polymorphic behaviour of solid phases of temperature range from 100 K to 340 K. The sample substances forming liquid crystals was reported also for mass amounted to 62.05 g (0.232 1 mole). PAA [4,5], , and for the esterpropyl-p-IR absorption spectra were measured on Zeiss UR-10 methoxybenzylidene -p -amino -a -methyl -cinnamic and Unicam SP-1200 spectrophotometers in the wave acid [7]. number range from 400 cm 1 to 3 600 cm 1 , and in the This paper presents a more detailed analysis of the temperature range from 80 K to 320 K. The resolution phase situation in MBBA and, in particular, a prelimi-was 3 cm -1 and 1 cm -1 for the first and second nary investigation of the kinetics of the monotropic spectrophotometer respectively.…”

Section: Introduction -Calorimetricmentioning

confidence: 99%

Calorimetric and Infra-Red Study of the Phase Situation in Solid Mbba

Janik

Mayer

et al. 1975

J. Phys. Colloques

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If MBBA is solidified by decreasing the temperature of the nematic phase, one obtains a metastable solid, whose specific heat vs. temperature curve has been measured by adiabatic calorimetry. This curve shows a sharp rise at melting. It also shows a quasi-second-order type of behaviour at about 210 K. If the metastable form of solid MBBA is kept for a few hours at a temperature not far below melting, it spontaneously transforms into the stable form, whose specific heat vs. temperature curve has also been measured. This curve lies below that of the metastable form and has a monotonic behaviour and a sharp rise at melting, which now occurs at a slightly higher temperature. Infra-red and far-infrared spectra of the two modifications of solid MBBA were also measured. In the internal vibration wave number region the spectra are significantly different in the whole temperature range. The quasi-second-order phase transition discovered in the metastable MBBA by calorimetry does not show up in IR. Differences between the spectra of the two modifications are greatest in the lattice vibration region, i. e. between 20 cm-1 and 100 cm-1. Preliminary powder X-ray diffraction data, obtained for the two modifications, show patterns typical of crystalline materials. The X-ray pattern changes significantly when the metastable MBBA transforms into the stable modification.

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Section: Introduction -Calorimetricmentioning

confidence: 99%

Calorimetric and Infra-Red Study of the Phase Situation in Solid Mbba

Janik

Mayer

et al. 1975

J. Phys. Colloques

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show abstract

“…Polymorphism of mesophase materials has been investigated (160) and factors influencing the results were discussed. Nematic compounds derived from cinnamic acid (149), aldonitrones (361), and Schiff bases (315) have been investigated. Decomposition temperatures for 19 amino acids have been determined (244) and polymorphism in several ^-substituted naphthalene derivatives was determined (237).…”

Section: Heats Of Fusion Have Been Measuredmentioning

confidence: 99%