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

Autori
Mihelj, Tea ; Popović, Jasminka ; Skoko, Željko ; Tomašić, Vlasta

Izvornik
Thermochimica acta (0040-6031) 591 (2014); 119-129

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
catanionic dodecylsulfates; thermotropism; basic lamellar thickness; tilt angle; multi-charged cationic surfactant; multi-tailed cationic surfactant

Sažetak
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.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA