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Designer Ionic Liquid Crystals Based on Congruently Shaped Guanidinium Sulfonates
Author(s) -
Butschies Martin,
Frey Wolfgang,
Laschat Sabine
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201101925
Subject(s) - mesophase , alkyl , crystallography , differential scanning calorimetry , sulfonate , iodide , ionic liquid , chemistry , bilayer , ionic bonding , mesogen , ion , inorganic chemistry , organic chemistry , polymer , liquid crystalline , sodium , phase (matter) , membrane , catalysis , thermodynamics , biochemistry , physics
Ionic liquid crystals are mesogenic compounds that consist of cations and anions, usually rod‐like cations and spherical anions. Herein we report a new method for the synthesis of ionic liquid crystals by using cations and anions of the same molecular shape with oppositely charged head groups. Thus, 4‐alkoxyphenylpentamethylguanidinium 4‐alkoxyphenylsulfonate ion pairs have been synthesised. 4‐Alkoxyphenylpentamethylguanidinium iodides were also prepared to determine the influence of congruently shaped anions, in comparison with their spherical counterparts, on mesophase behaviour, which was investigated by differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X‐ray diffraction (XRD). All the liquid crystalline salts exhibit smectic A mesophases with strongly interdigitated bilayer structures. The guanidinium sulfonate ion pairs show mesomorphic properties from shorter alkyl chain lengths (≥C 9 ) and lower melting points (≈10 K), whereas the corresponding guanidinium iodides are liquid crystalline for longer alkyl chain lengths (≥C 14 ). For chains with ≥C 18 , however, the mesophase range decreases for the sulfonate ion pairs, but not for the iodide salts.