Mesomorphism of a new series of catanionic 4-(1- pentylheptyl)benzenesulfonates

Tomašić, Vlasta; Mihelj, Tea; Zhang, Ruibin; Liu, Feng; Ungar, Goran (2014) Mesomorphism of a new series of catanionic 4-(1- pentylheptyl)benzenesulfonates. Soft matter, 10 . pp. 7887-7896. ISSN 1744-683X

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Abstract

The effect of cationic chemical structure on the mesophase behavior, and self-assembly of catanionic compounds is studied through a systematic structure variation of six cationic surfactants with anionic sodium 4-(1- pentylheptyl)benzenesulfonate surfactant. A series of cationic surfactants are selected with increasing number of n-dodecyl chains on the same ammonium headgroup (from one to three), and with increasing number of ammonium headgroups (from two to four). Thermal and phase behavior of the synthesized products were examined by thermogravimetry, polarizing microscopy, differential scanning calorimetry, powder and grazing incidence X-ray diffraction, and molecular simulation. The compounds are complexes of high thermal stability. Most of the thermotropic mesophases are smectic, although the hexagonal mesophase is also observed. Introduction of the third dodecyl chain into the cationic part causes pronounced lower melting temperatures and eradicates mesomorphism, while the addition of a fourth ammonium headgroup leads to a catanionic benzenesulfonate that decomposes simultaneously with melting. Melting and crystallization temperatures show nonlinear dependence on the total number of alkyl chains, and on the number of headgroups in the molecule. Molecular dynamics simulation of the smectic phase points to separated hydrophilic and hydrophobic layers, favoring head-to-head packing of antiparallel molecules. On the other hand, there are two ion pairs in the column cross- section of the hexagonal LC phase of didodecyldimethylammonium-4-(1- pentylheptyl)benzenesulfonate.

Item Type:	Article
Uncontrolled Keywords:	catanionic surfactant ; thermotropic mesomorphism ; small angle X-ray scattering ; 4-(1-pentylheptyl)benzenesulfonate
Subjects:	NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Chemistry > Physical Chemistry
Divisions:	Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Surfactants, processes in solutions and at interfaces (Površinski aktivne tvari, procesi u otopinama i na međupovršinama)- Maja Dutour Sikirić 098-0982915-2949 MZOS
Depositing User:	Tea Mihelj
Date Deposited:	01 Dec 2015 08:16
URI:	http://fulir.irb.hr/id/eprint/2344
DOI:	10.1039/C4SM01356E

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