Naslov
Effect of the Spacer Length on the Solid Phase Transitions of Asymmetric Gemini Surfactants

Autori
Sikirić, Maja ; Šmit, Ivan ; Tušek-Božić, Ljerka ; Primožič, Ines ; Filipović-Vinceković, Nada

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
XVIII. Hrvatski skup kemičara i kemijskih inženjera : sažeci / Zrnčić, Hrvoje - Zagreb : Hrvatsko društvo kemijskih inženjera i tehnologa (HDKI) ; Hrvatsko kemijsko drustvo, 2003, 29-29

ISBN
953-65894-08-4

Skup
XVIII. Hrvatski skup kemičara i kemijskih inženjera

Mjesto i datum
Zagreb, Hrvatska, 16.02.2003. - 19.02.2003

Vrsta sudjelovanja
Poster

Vrsta recenzije
Domaća recenzija

Ključne riječi
gemini surfactants ; thermal properties ; polymorphism ; thremotropic liquid crystals

Sažetak
Three quaternary, asymmetric, dimeric surfactants with two hydrocarbon chains differing in length (tetradecyl and dodecyl) and with different polymethylene spacers N, N, N&cent , N&cent -tetramethylethane (12-2-14), N, N, N&cent , N&cent -tetramethylehexane (12-6-14) and N, N, N&cent , N&cent - tetramethyldecane (12-10-14) were prepared. Their solid phase and thermal behavior were examined by X-ray diffraction, spectral, thermal and optical microscopic studies. Structure of 12-2-14 contains interdigitated alkyl chain layers, 12-6-14 monolayers of molecules with tilted alkyl chains, while 12-10-14 exhibits liquid crystalline structure even at room temperature. Molecules with a shorter spacer are all in cis-configuration, while those with longer ones are all in trans-configuration. On heating all compounds exhibited the conformational disordering of the alkyl chain during phase transitions in the solid state at lower temperatures and the bidimensional disordering of the ionic layers during the solid crystalline to liquid crystalline transitions. Phase transitions in the solid state include structural varieties, polymorphs and smectic liquid crystals. Crystal structure, number of phase transitions and thermodynamic parameters strongly depend on the spacer length ; i.e., on the global configuration of molecules. Temperatures of the first solid state, solid crystal &#8211 liquid crystal and liquid crystal &#8211 isotropic melt transitions exhibit maximum for s = 6. Polarizing microscopy revealed characteristic textures of the smectic phases in the case of 12-2-14 and 12-10-14.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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