engleski

Solid phase transitions of n-alkylammonium cholates

Novel series of catanionic surfactants n-alkylammonium cholates (the number of carbon atoms per chain being n = 10, 12, 14, 16) was prepared and characterized by elemental and thermogravimetric analysis, IR and NMR spectroscopy. The influence of the alkyl chain length on the structural and thermal properties was investigated by means of polarizing microscopy, differential scanning calorimetry and X-ray diffraction. All compounds exhibited a complex polymorphism and thermotropic mesomorphis from the stable crystalline form to the isotropic phase. On heating two main phase transition transition were observed for all compounds: solid to liquid crystalline phase transition and isotropization. The liquid crystalline phases exhibited textures characteristic for smectic A phase (SA). The extent of crystallinity, temperatures of phase transitions, thermodynamic parameters, and basic lamellar thickness varied linearly with the increase of the alkylammonium chain length.

catanionic surfactants; solid phase transitions

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