Evidence of Counterion Size Effect on the Stability of Columnar Phase of Ionic Liquid Crystals Based on Pyridinium Salts Derived from <i>N</i>-3,4,5-Tri(alkyloxy)-benzyl-4-pyridones
Isabela Dumitru,
Florentina L. Chiriac,
Monica Ilis,
Iuliana Pasuk,
Doina Manaila-Maximean,
Marin Micutz,
Teodora Staicu,
Viorel Cîrcu
Affiliations
Isabela Dumitru
Department of Inorganic Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd., 030018 Bucharest, Romania
Florentina L. Chiriac
Department of Inorganic Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd., 030018 Bucharest, Romania
Monica Ilis
Department of Inorganic Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd., 030018 Bucharest, Romania
Iuliana Pasuk
National Institute of Materials Physics, P.O. Box MG-7, 077125 Magurele, Romania
Doina Manaila-Maximean
Department of Physics, University Politehnica of Bucharest, Spl. Independentei 313, 060042 Bucharest, Romania
Marin Micutz
Department of Physical Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd., 030018 Bucharest, Romania
Teodora Staicu
Department of Physical Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd., 030018 Bucharest, Romania
Viorel Cîrcu
Department of Inorganic Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd., 030018 Bucharest, Romania
The synthesis and characterization of novel ionic liquid crystals based on pyridinium salts with Br− and PF6− counterions are described in this work. These pyridinium salts were derived from 4-hydroxypyridine, both by N- and O-alkylation. The 3,4,5-tri(alkyloxy)-benzyl mesogenic unit was attached to the nitrogen atom of the pyridinium ring. Alkyl chains with a different number of carbon atoms (6, 8, 10, 12 and 14) were employed in order to show the effect on the stability of mesophase. The POM (polarizing optical microscopy) and XRD (powder X-ray diffraction) studies indicated that bromide salts with shorter chains C6, C8 and C10 do not show mesomorphic properties, while longer chain analogues with C12 and C14 exhibit two enantiotropic columnar phases. Surprisingly, the pyridinium salts with the larger size PF6− counterion do not exhibit liquid crystal properties.
