Structural Parameters of Lamellar Phases Formed by the Self-Assembly of Dialkyldimethylammonium Bromides in Aqueous Solution

Ferreira, Guilherme A.; Loh, Watson

doi:10.5935/0103-5053.20150297

Cited by 15 publications

(33 citation statements)

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“…DODAB arranges itself into a swollen lamellar phase (d sp = 126 Å) when heated above its melting temperature, resulting in a bilayer thickness of 30 Å and a surfactant molecule area of 68 Å 2 . This is in line with the expected decrease from a “solid-like” to “fluid-like” hydrocarbon state, assuming that all chains are in an all-trans conformation, and are perpendicular to the interface in the L β phase, and are in a liquid hydrocarbon state and perpendicular to the interface in the L α phase [ 45 , 46 ].…”

Section: Resultssupporting

confidence: 80%

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

2021

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Double-chain amphiphilic compounds, including surfactants and lipids, have broad significance in applications like personal care and biology. A study on the phase structures and their transitions focusing on dioctadecyldimethylammonium chloride (DODAC), used inter alia in hair conditioners, is presented. The phase behaviour is dominated by two bilayer lamellar phases, Lβ and Lα, with “solid” and “melted” alkyl chains, respectively. In particular, the study is focused on the effect of additives of different polarity on the phase transitions and structures. The main techniques used for investigation were differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS and WAXS). From the WAXS reflections, the distance between the alkyl chains in the bilayers was obtained, and from SAXS, the thicknesses of the surfactant and water layers. The Lα phase was found to have a bilayer structure, generally found for most surfactants; a Lβ phase made up of bilayers with considerable chain tilting and interdigitation was also identified. Depending mainly on the polarity of the additives, their effects on the phase stabilities and structure vary. Compounds like urea have no significant effect, while fatty acids and fatty alcohols have significant effects, but which are quite different depending on the nonpolar part. In most cases, Lβ and Lα phases exist over wide composition ranges; certain additives induce transitions to other phases, which include cubic, reversed hexagonal liquid crystals and bicontinuous liquid phases. For a system containing additives, which induce a significant lowering of the Lβ–Lα transition, we identified the possibility of a triggered phase transition via dilution with water.

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Section: Resultssupporting

confidence: 80%

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

2021

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“…Fig. 3) both give rise to a sharp reflection at 4.11 Å which is indicative of a liquid crystalline (L α ) gel phase, and testifies to alkyl chains that are packed in an hexagonal array and have freedom to rotate about their long axes 12,13,[25][26][27][28] . The same sharp reflection is seen in the WAXS patterns recorded for the 10% w/w ternary system (see Fig.…”

Section: Resultsmentioning

confidence: 90%

Revealing the Hidden Details of Nanostructure in a Pharmaceutical Cream

Ahmadi

Mahmoudi

et al. 2020

Sci Rep

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Creams are multi-component semi-solid emulsions that find widespread utility across a wide range of pharmaceutical, cosmetic, and personal care products, and they also feature prominently in veterinary preparations and processed foodstuffs. The internal architectures of these systems, however, have to date been inferred largely through macroscopic and/or indirect experimental observations and so they are not well-characterized at the molecular level. Moreover, while their long-term stability and shelflife, and their aesthetics and functional utility are critically dependent upon their molecular structure, there is no real understanding yet of the structural mechanisms that underlie the potential destabilizing effects of additives like drugs, anti-oxidants or preservatives, and no structure-based rationale to guide product formulation. In the research reported here we sought to address these deficiencies, making particular use of small-angle neutron scattering and exploiting the device of H/D contrast variation, with complementary studies also performed using bright-field and polarised light microscopy, smallangle and wide-angle X-ray scattering, and steady-state shear rheology measurements. through the convolved findings from these studies we have secured a finely detailed picture of the molecular structure of creams based on Aqueous Cream BP, and our findings reveal that the structure is quite different from the generic picture of cream structure that is widely accepted and reproduced in textbooks. Oil-in-water creams are widely used in pharmaceutical products formulated to treat conditions like atopic dermatitis, rosacea and psoriasis 1. They also form the basis of veterinary medications used to assist wound-healing and treat skin infections 2 , and they are the basis too of a great many personal care products, spanning make-up foundations, anti-perspirants, sun lotions and deodorants 3. All such products are complex, multi-component colloids in which the constituent oil and water phases are stabilised through the addition of one or more ionic, non-ionic or zwitterionic surfactants, in combination with one or more co-surfactants (sometimes referred to as consistency enhancers) which might be long chain fatty acids, fatty alcohols or monoglycerides 4,5. Other components which might be added include humectants such as propylene glycol, anti-oxidants like α-tocopherol acetate, and preservatives like phenoxyethanol 6. The molecular architecture of any given cream formulation will clearly vary according to its chemical composition, and this in turn will determine its chemical and physical stability, and also impact the cream's sensory aesthetics and efficacy as a cosmetic, pharmaceutical, or veterinary product. Despite much research into the properties of creams and their many years of use, however, our understanding of their internal molecular structure is still far from complete, with the unavoidable consequence, therefore, that they are still formulated only in a semi-empirical manner. Junginger and co-workers 7 ...

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“…As far as we know, the reason for such an effect is not clear. Here, we hypothesize that such a pretransition may be related to the energy required to remove the interdigitated state of DODAB bilayers (Feitosa et al, ; Ferreira and Loh, ; Jamroz et al, ), while the DODAC bilayer displays no interdigitate state and, therefore, no pretransition (Feitosa et al, ). Of course, such a hypothesis should be proved, a task that is beyond the scope of the present study.…”

Section: Resultsmentioning

confidence: 99%

Mixed Cationic Surfactant Vesicles in (Dioctadecyldimethylammonium Bromide)/NaCl and (Dioctadecyldimethylammonium Chloride)/NaBr Aqueous Dispersions

Feitosa

Lemos

Adati

2019

J Surfact & Detergents

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One of the most challenging characteristics not fully understood yet of the cationic surfactant salt dioctadecyldimethylammonium (DODA+) halide is concerned with the effects of the counterion (usually Br− and Cl−) on the surfactant assembly into vesicle structures in aqueous solution. These counterions play a key role in the self‐organization of DODA+ into bilayer structures. Differential scanning calorimetry (DSC) and dynamic light scattering (DLS) techniques were used here to investigate systematically the effects of the single salts NaCl and NaBr, respectively, on the thermal behavior and structural organization of the cationic dioctadecyldimethylammonium bromide and chloride (DODAB and DODAC) in water. The results undoubtedly indicate that the added Br− or Cl−, respectively, into DODAC and DODAB aqueous dispersions, replaces partially the bound counterions (Cl− and Br−) from the vesicles, yielding formation of DODAB/DODAC mixed vesicles. As a conclusion, single salts may be used to tune the thermal and structural characteristics of cationic vesicles.

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Structural Parameters of Lamellar Phases Formed by the Self-Assembly of Dialkyldimethylammonium Bromides in Aqueous Solution

Cited by 15 publications

References 0 publications

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

Revealing the Hidden Details of Nanostructure in a Pharmaceutical Cream

Mixed Cationic Surfactant Vesicles in (Dioctadecyldimethylammonium Bromide)/NaCl and (Dioctadecyldimethylammonium Chloride)/NaBr Aqueous Dispersions

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