Study of some defects observed in the hexagonal liquid crystals
Description
A polarising microscopy study of the disclinations in an hexagonal discotic liquid crystal (hexa-pentoxy-triphenylene) allows us to confirm the theory of the developable domains and the existence of the disclinations as involute of the circle. The absence of the lines S = 1 leads us to propose a model of core in which the energetic instability of these lines is emphasized. The nature of the core is discussed: it is probably filled with hexagonal liquid crystal. Moreover the birefringence Δn is measured and a first estimate of the anchoring energies of the discotic both on the glass and in contact with the air is given. The Michelson interferometry study of the interaction between the disclinations and the free surface has allowed to observe a strong anisotropy of the interfacial tension. At last a study of the walls leads to a classification according to the matching angle and to a first estimate of the penetration distance λ. A similar study has been undertaken in an inverse middle liquid crystalline phase (Na dioctylsulfosuccinate). A strong dependence of the elastic constants with the water concentration is observed. The micellar → hexagonal transition is studied. (author)
Abstract (French)
L'etude au microscope polarisant des lignes diedre dans un cristal liquide hexagonal discotique (hexapentoxytriphenylene) a permis de confirmer la theorie des domaines developpables et de montrer l'existence des lignes diedre S = 1/2 en developpantes de cercle. L'absence de ligne S = 1 a conduit a developper un modele de coeur dans lequel l'instabilite energetique de ces lignes est mise en evidence. La nature du coeur est discutee: il est probablement rempli de cristal liquide hexagonal pur. D'autre part, la birefringence Δn est mesuree et nous donnons une premiere estimation des energies d'ancrage du discotique sur le verre non traite et au contact de l'air. C'est en etudiant en interferometrie Michelson l'interaction des disinclinaisons avec la surface libre que nous avons pu mettre en evidence une forte anisotropie de la tension interfaciale. Enfin une etude de parois a permis de les classifier en fonction de l'angle de raccordement et de donner une premiere estimation de la distance de penetration λ. Une etude analogue a ete entreprise dans un hexagonal inverse lyotrope (dictylsulfosuccinate de sodium). La forte dependance des constantes elastiques avec la concentration en eau est mise en evidence. La transition micellaire → hexagonal est etudiee. (auteur)Files
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Additional details
Additional titles
- Original title (French)
- Etude de quelques defauts observes dans les cristaux liquides hexagonaux
Identifiers
Publishing Information
- Imprint Pagination
- 87 p.
- Report number
- CEA-N--2233
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 45084302
- Subject category
- S75: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- BIREFRINGENCE; CRYSTAL DEFECTS; DOMAIN STRUCTURE; ELASTICITY; ENERGY DENSITY; HCP LATTICES; INCLINATION; LIQUID CRYSTALS; MICHELSON INTERFEROMETER; PENETRATION DEPTH; SURFACE TENSION; TRIPHENYLENE
- Descriptors DEC
- AROMATICS; CONDENSED AROMATICS; CRYSTAL LATTICES; CRYSTAL STRUCTURE; CRYSTALS; FLUIDS; HEXAGONAL LATTICES; HYDROCARBONS; INTERFEROMETERS; LIQUIDS; MEASURING INSTRUMENTS; MECHANICAL PROPERTIES; ORGANIC COMPOUNDS; REFRACTION; SURFACE PROPERTIES
Optional Information
- Notes
- 20 refs.; Available from the INIS Liaison Officer for France, see the 'INIS contacts' section of the INIS website for current contact and E-mail addresses: http://www.iaea.org/inis/Contacts/