Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.21/709
Título: Shear-induced lamellar ionic liquid-crystal foam
Autor: Ferreira, A. J.
Cruz, C.
Godinho, M. H.
Kulkarni, P. S.
Afonso, C. A. M.
Teixeira, Paulo Ivo Cortez
Palavras-chave: Liquid foams
Ionic liquid crystals
Data: 2010
Editora: Taylor & Francis LTD
Citação: Ferreira A J, Cuz C, Godinho M H, Kukkarni P S, Afonso C A M, Teixeira P I C. Shear-induced lamellar ionic liquid-crystal foam. Liquid Crystals. 2010; 37 (4): 377-382.
Relatório da Série N.º: 4;
Resumo: n a recent paper we reported an experimental study of two N-alkylimidazolium salts. These ionic compounds exhibit liquid crystalline behaviour with melting points above 50 degrees C in bulk. However, if they are sheared, a (possibly non-equilibrium) lamellar phase forms at room temperature. Upon shearing a thin film of the material between microscope slides, textures were observed that are strikingly similar to liquid (wet) foams. The images obtained from polarising optical microscopy (POM) were found to share many of the known quantitative properties of a two-dimensional foam coarsening process. Here we report an experimental study of this foam using a shearing system coupled with POM. The structure and evolution of the foam are investigated through the image analysis of time sequences of micrographs obtained for well-controlled sets of physical parameters (sample thickness, shear rate and temperature). In particular, we find that there is a threshold shear rate below which no foam can form. Above this threshold, a steady-state foam pattern is obtained where the mean cell area generally decreases with increasing shear rate. Furthermore, the steady-state internal cell angles and distribution of the cell number of sides deviate from their equilibrium (i.e. zero-shear) values.
Peer review: yes
URI: http://hdl.handle.net/10400.21/709
ISSN: 0267-8292
Aparece nas colecções:ISEL - Física - Artigos

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