Dimethyldioctadecylammonium bromide (also dioctadecyldimethylammonium bromide or DODAB) is a double-chained quaternary ammonium
surfactant
Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word ''surfactant'' is a Blend word, blend of "surface-active agent",
coined in ...
that forms unilamellar
vesicles
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane
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In a neuron, synaptic vesicles (or neurotransmitter vesicles) s ...
(ULVs) in water. Among various preparation methods, the ‘‘hot-water” method offers a simple procedure to prepare DODAB
cationic
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
vesicles by simply dissolving the DODAB in hot water above 50 °C, i.e., chain melting (main)
transition, Tm.
In general, the
DSC DSC or Dsc may refer to:
Education
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thermograms of the unsonicated DODAB
dispersions are dominated by two endotherms; the pre- (35–36 °C) and main transition (42.7–45 °C) peaks. Moreover, in literature reported the presence of a third
endotherm (post transition) at 52.2 °C.
The main transition (Tm) is ascribed to
gel to liquid-crystalline phase transition in which the alkyl chains transform from solidlike to liquid-like state.
The 10 mM DODAB is a critical
concentration
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'', ...
, below which the dispersions consist of large polydispersed unilamellar vesicles (ULVs) that exhibit a local (chain melting) transition at 43 °C, beyond which a structural transition occurs: ULVs --> MLVs (multilamellar vesicles) as indicated by the sudden increase in the dynamic moduli. However, above 10 mM DODAB, the dispersions are mostly formed by ULVs in coexistence with lamellar fragments resulting in a network that shows a rheogram similar to that of hexagonal liquid-crystalline phase.
[Coppola L. , Youssry M. , Nicotera I. , Gentile L. , " Rheological investigation of thermal transitions in vesicular dispersion". Journal of Colloid and Interface Science, 2009, Vol. 338, n. 2, pp. 550–557]
Abstract
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See also
* Cetyl trimethylammonium bromide (CTAB) a.k.a. hexadecyl trimethyl ammonium bromide,
* Cetyl trimethylammonium chloride (CTAC)
* Dimethyldioctadecylammonium chloride
Dimethyldioctadecylammonium chloride (also commonly distearyl dimethyl ammonium chloride or distearyldimonium chloride) is an organic compound classified as quaternary ammonium salt. The nitrogen center substituted with two methyl groups and two ...
– corresponding chloride salt
* Didecyldimethylammonium chloride – shorter di-C10 analogue
References
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Colloidal chemistry
Soft matter
Ammonium compounds
Bromides
Cationic surfactants