Cholesteric textures observed by transmission electron microscopy in diffraction contrast

Pierron, Jean; Böudet, Alain M.; Sopéna, P.; Mitov, Michel; Sixou, P.

doi:10.1080/02678299508031977

Cited by 23 publications

(30 citation statements)

References 21 publications

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“…3b). The structure shows up as parallel lines alternatively bright and dark, regularly spaced in a periodic arrangement, as already seen in our previous study on bulky SB samples [3]. Here these lines are very well oriented all over the section, parallel to the outer boundary delimited by the glass slide.…”

Section: Transmission Electron Microscopysupporting

confidence: 51%

“…The visible light transmission spectrums from these films stated the efficiency of the process. In the present paper, we demonstrate that this efficiency is related to the particular structure of the cholesteric films, by means of observations by transmission electron microscopy, which was proven to provide well-contrasted images of the cholesteric structure [3].…”

Section: Cholesteric Films With Extended Bandwidth Light Reflectionmentioning

confidence: 99%

“…In the subsequent and present study, the observations were conducted in TEM on thin slices regularly sectioned in the specimen by ultramicrotomy. This technique was chosen because it has proven to give excellent images in previous studies, well contrasted and reproducible [3,12,13]. The investigations were carried out on the morphology of liquid-crystal polymers and polymer-dispersed liquid crystals.…”

Section: Cholesteric Films With Extended Bandwidth Light Reflectionmentioning

confidence: 99%

“…The investigations were carried out on the morphology of liquid-crystal polymers and polymer-dispersed liquid crystals. In reference [3], the origin of the contrast of a cholesteric substance, analogous to that studied here, made of alternated bright and dark lines, was investigated and discussed. Two types of the origin of contrast were analysed, diffraction contrast and irradiation contrast.…”

Section: Cholesteric Films With Extended Bandwidth Light Reflectionmentioning

confidence: 99%

“…The observations were carried out in a transmission electron microscope Philips CM12 performed at room temperature and in normal conditions. This means that the dose of electrons received by the specimen is well higher than the critical dose deleting the diffraction contrast, and that the images are produced by a thickness diffusion contrast subsequent to irradiation [3]. The contrast was enhanced by a slight defocus.…”

Section: Transmission Electron Microscopymentioning

confidence: 99%

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Microstructure of variable pitch cholesteric films and its relationship with the optical properties

et al. 2000

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A way to make cholesteric films reflecting in a broad wavelength band consists in associating different cholesteric pitches in the same film. In two previous papers, we proposed an efficient method to produce variable pitch films, based on a thermal processing, and we studied the optical properties of these films with respect to the time of processing. In the present paper, we study the microstructure of such films with respect to the processing time by means of transmission electron microscopy. The cholesteric phase is shown to be very well ordered. Within a wide range of annealing times, its periodicity is progressive from one face to the other of the film. A description of the evolution of the structure with respect to the processing time is given, and classified in three stages, corresponding to the three stages already stated from the optical properties. The relationship between the evolution of the structure and the optical properties is discussed. PACS. 61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures -61.30.-v Liquid crystals -61.16.Bg Transmission, reflection and scanning electron microscopy (including EBIC)

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Section: Transmission Electron Microscopysupporting

confidence: 51%

Section: Cholesteric Films With Extended Bandwidth Light Reflectionmentioning

confidence: 99%

Section: Cholesteric Films With Extended Bandwidth Light Reflectionmentioning

confidence: 99%

Section: Cholesteric Films With Extended Bandwidth Light Reflectionmentioning

confidence: 99%

Section: Transmission Electron Microscopymentioning

confidence: 99%

See 3 more Smart Citations

Microstructure of variable pitch cholesteric films and its relationship with the optical properties

et al. 2000

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Small Organic Molecules and Higher Homologs

Kolb

Gorelik

2012

Handbook of Nanoscopy

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Cholesteric Liquid Crystals with a Broad Light Reflection Band

2012

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The cholesteric-liquid-crystalline structure, which concerns the organization of chromatin, collagen, chitin, or cellulose, is omnipresent in living matter. In technology, it is found in temperature and pressure sensors, supertwisted nematic liquid crystal displays, optical filters, reflective devices, or cosmetics. A cholesteric liquid crystal reflects light because of its helical structure. The reflection is selective - the bandwidth is limited to a few tens of nanometers and the reflectance is equal to at most 50% for unpolarized incident light, which is a consequence of the polarization-selectivity rule. These limits must be exceeded for innovative applications like polarizer-free reflective displays, broadband polarizers, optical data storage media, polarization-independent devices, stealth technologies, or smart switchable reflective windows to control solar light and heat. Novel cholesteric-liquid-crystalline architectures with the related fabrication procedures must therefore be developed. This article reviews solutions found in living matter and laboratories to broaden the bandwidth around a central reflection wavelength, do without the polarization-selectivity rule and go beyond the reflectance limit.

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Cholesteric textures observed by transmission electron microscopy in diffraction contrast

Cited by 23 publications

References 21 publications

Microstructure of variable pitch cholesteric films and its relationship with the optical properties

Microstructure of variable pitch cholesteric films and its relationship with the optical properties

Small Organic Molecules and Higher Homologs

Cholesteric Liquid Crystals with a Broad Light Reflection Band

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