Thermotropic phase transitions of catanionic dodecylsulfates with multi-charged and multi-tailed quaternary ammonium centers

Mihelj, Tea; Popović, Jasminka; Skoko, Željko; Tomašić, Vlasta (2014) Thermotropic phase transitions of catanionic dodecylsulfates with multi-charged and multi-tailed quaternary ammonium centers. Thermochimica acta, 591 . pp. 119-129. ISSN 0040-6031

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Abstract

Five novel anhydrous catanionic dodecylsulfates containing multi-charged and multi-tailed quaternary ammonium centers were synthesized and examined with light microscopy, differential scanning calorimetry and X-ray powder diffraction. This study is an attempt to explain the relationship between chemical structure, resulting molecular architecture, phase transition energetics, and intermolecular interactions of the individual amphiphiles that ultimately lead to mesomorphic product. All examined compounds are of typical layered structure at room temperature. The dimeric didodecylsulfate crystallizes in monoclinic, while trimeric tridodecylsulfate in triclinic crystal system, as obtained by X-ray powder diffraction. The long spacing, d/Å, decreases linearly with the increase of the ionic head number, and of n-dodecyl chain number. The thermal analysis of the samples indicates rich thermal behavior with thermotropic mesomorphism and polymorphism for all examined catanionics, as well as isotropisation accompanied by decomposition for three-headed and three-tailed dodecylsulfates. Their thermal behavior is greatly promoted by the quaternary ammonium centers. Examined catanionics show thermotropic phases over a broader temperature range due to the ability to accommodate chain disorder and strong ionic interactions. Maltese crosses, oily streaks textures, stepped drops and fan-shaped textures affirmed the existence of various smectic mesophases.

Item Type:	Article
Uncontrolled Keywords:	catanionic dodecylsulfates ; thermotropism ; basic lamellar thickness ; tilt angle ; multi-charged cationic surfactant ; multi-tailed cationic surfactant
Subjects:	NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Chemistry > Physical Chemistry
Divisions:	Division of Materials Physics Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Structure and properties of selected nanomaterials obtained by modern techniques (Struktura i svojstva posebnih nanomaterijala dobivenih suvremenim tehnikama)- Antun Tonejc 119-0982886-1009 MZOS Mathematical description of molecular structure, dinamics and reactivity (Razvoj matematičkih metoda za opis strukture, dinamike i reaktivnosti molekula)- Darko Babić 098-0982915-2942 MZOS
Depositing User:	Tea Mihelj
Date Deposited:	30 Nov 2015 15:39
URI:	http://fulir.irb.hr/id/eprint/2337
DOI:	10.1016/j.tca.2014.07.024

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