The thermotropic liquid crystals formed by anhydrous sodium ricinoleate

Narayan, K. S.; Shinde, Neeta; Tiddy, G. J. T.; Holmes, Michael C.

doi:10.1080/02678299408037333

Cited by 6 publications

(9 citation statements)

References 21 publications

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“…Skoulios, Luzatti, and co-workers have reported similar phases for soaps many years ago, − while more recently such phases have been observed even in the presence of a nonpolar solvent . It appears that a wide range of mesophases can occur, comprising various smectic arrangements as observed here and previously by Alami et al , or ordered rod/globular aggregate structures as observed with various soaps. − This area merits a systematic investigation, where headgroup structure and alkyl chain shape (branching) are varied. Perhaps the most surprising result is that Alami et al did not observe thermotropic mesophases in their previous studies of the n-m-n compounds.…”

Section: Resultsn-m-n Compoundssupporting

confidence: 70%

Thermotropic and Lyotropic Mesophase Behavior of Amphitropic Diammonium Surfactants

Fuller¹,

Shinde²,

Tiddy³

et al. 1996

Langmuir

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We have synthesized two series of gemini diammonium surfactants with chain terminating poxycyanobiphenyl (OCB) groups (I) or conventional structures (II). The thermotropic mesomorphic behavior of series II has been examined using optical microscopy, differential scanning calorimetry, and X-ray diffraction. All the compounds form one or more smectic phases, at least one of which resembles the smectic T (S T) phase reported by Alami et al. (Liq. Cryst., 1993, 13, 201), where the ionic headgroups form an ordered array, but the chains have some disorder. The exact chain packing differs from that of the ST structure. The lyotropic mesophases formed with water have been investigated for both I and II by optical microscopy and X-ray diffraction (I only). Series II compounds form hexagonal (H1), intermediate (INT) and/or cubic (V1) and lamellar (LR) phases; the size of the spacer group (m) has little influence on this. The OCB compounds all form LR as the only lyotropic mesophase. These results show that the insertion of the rigid terminal OCB moiety has a much larger influence on mesophase structure (and by implication on micelle shape) than the spacer group for m e 6.

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Section: Resultsn-m-n Compoundssupporting

confidence: 70%

Thermotropic and Lyotropic Mesophase Behavior of Amphitropic Diammonium Surfactants

Fuller¹,

Shinde²,

Tiddy³

et al. 1996

Langmuir

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“…The exact shape of the colloidal 2D sheets cannot be assessed at this stage. Early work by Narayan et al has suggested disc-shaped aggregates upon heating sodium ricinoleate . The domain sizes of the colloidal assembly were evaluated using the Scherrer equation to be ca.…”

Section: Resultsmentioning

confidence: 99%

Heating-Induced Switching to Hierarchical Liquid Crystallinity Combining Colloidal and Molecular Order in Zwitterionic Molecules

Gustavsson,

Lv,

Cherian

et al. 2023

ACS Omega

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Hierarchical self-assemblies of soft matter involving triggerable or switchable structures at different length scales have been pursued toward multifunctional behaviors and complexity inspired by biological matter. They require several and balanced competing attractive and repulsive interactions, which provide a grand challenge in particular in the “bulk” state, i.e., in the absence of plasticizing solvents. Here, we disclose that zwitterionic bis-n-tetradecylphosphobetaine, as a model compound, shows a complex thermally switchable hierarchical self-assembly in the solvent-free state. It shows polymorphism and heating-induced reversible switching from low-temperature molecular-level assemblies to high-temperature hierarchical self-assemblies, unexpectedly combining colloidal and molecular self-assemblies, as inferred by synchrotron small-angle X-ray scattering (SAXS). The high-temperature phase sustains birefringent flow, indicating a new type of hierarchical thermotropic liquid crystallinity. The high-temperature colloidal-level SAXS reflections suggest indexation as a 2D oblique pattern and their well-defined layer separation in the perpendicular direction. We suggest that the colloidal self-assembled motifs are 2D nanoplatelets formed by the lateral packing of the molecules, where the molecular packing frustration between the tightly packed zwitterionic moieties and the coiled alkyl chains demanding more space limits the lateral platelet growth controlled by the alkyl stretching entropy. An indirect proof is provided by the addition of plasticizing ionic liquids, which relieve the ionic dense packings of zwitterions, thus allowing purely smectic liquid crystallinity without the colloidal level order. Thus, molecules with a simple chemical structure can lead to structural hierarchy and tunable complexity in the solvent-free state by balancing the competing long-range electrostatics and short-range nanosegregations.

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“…Another peculiar aspect for the 6-mLys-6 surfactant is that poorly defined and broad Bragg reflections (Figure a) are seen for the crystalline solid, where molecules should be highly organized in rods, with fully crystallized hydrocarbon chains. , There is also an isotropic band at 76.7 °C centered in a high q -value (4.40 nm −1 ). These broad peaks could be due to the formation of relatively short rods (or large globular aggregates) in a hexagonal array where the ratio between the major and minor axis is close to 1. ,, …”

Section: Discussionmentioning

confidence: 99%

“…The measured chain length exceeds just slightly the theoretical length of a fully elongated C12 chain. When compared to similar surfactants, ,, it can be expected that a slight deformation at the spacer region occurs. The spacer could be slightly bent, with one hydrocarbon chain being more deeply inserted in the hydrophobic region than the other, therefore increasing slightly the bilayer thickness.…”

Section: Discussionmentioning

confidence: 99%

“…These broad peaks could be due to the formation of relatively short rods (or large globular aggregates) in a hexagonal array where the ratio between the major and minor axis is close to 1. 28,47,48 Regarding 10-mLys-10, the preferred crystalline structure is a layered smectic one. Upon heating, a smectic phase is formed (Figure 6C), coexisting nevertheless with traces of a reverse hexagonal phase (Figure 7b and Table 1).…”

Section: Molecular Shape and Sequence Of Liquid-crystalline Phasesmentioning

confidence: 99%

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Structure/Property Relationships for the Thermotropic Behavior of Lysine-Based Amphiphiles: from Hexagonal to Smectic Phases

et al. 2008

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Amino acid-derived gemini surfactants arise as a potentially good alternative to the more conventional lipid and synthetic catanionic systems in view of their enhanced interfacial properties, increased chemical stability, and low toxicity. The presence of an amino acid as the polar headgroup allows toxicity reduction, with the simultaneous increase of biodegradability. For these compounds, the establishment of structure/function relationships from the assessment of their basic aggregation properties is therefore of the utmost interest, e.g., in the design of operative self-assembled systems (e.g., liposomes, nanotubes, etc). In this context, the study of the thermal phase behavior of the dry surfactants is a natural, straightforward first step, the more so as thermotropic liquid crystals are also relevant for practical applications. In this work, several lysine-based amphiphiles with a gemini-like configuration have been synthesized, with the amino acid side chain as the spacer group. The molecules are either esters (neutral, with C6-C12 even chains) or sodium carboxylates (anionic, with C6-C12 even chains). Upon increasing the temperature, different crystalline (cr) and liquid-crystalline (lc) phases have been detected and the corresponding thermodynamic and structural parameters determined by a combination of differential scanning calorimetry, polarizing light microscopy and small-angle X-ray scattering. The phase behavior of the amphiphiles is highly dependent on both the chain length and the presence of charge on the headgroup, with significant differences occurring within and between each group of molecules. The C6 and C8 esters form reverse hexagonal cr and lc phases, while C10 and C12 self-assemble into smectic cr and lc structures, with C10 showing also a reverse hexagonal lc phase prior to isotropization. All the carboxylate derivatives form smectic lc phases at high enough temperature prior to isotropization. The rationalization of the phase behavior and phase transition energetics of the compounds has been put forth on the basis of the intermolecular interactions at stake (van der Waals, H-bonding, electrostatic, and packing) and the molecular shape of the amphiphile.

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The thermotropic liquid crystals formed by anhydrous sodium ricinoleate

Cited by 6 publications

References 21 publications

Thermotropic and Lyotropic Mesophase Behavior of Amphitropic Diammonium Surfactants

Thermotropic and Lyotropic Mesophase Behavior of Amphitropic Diammonium Surfactants

Heating-Induced Switching to Hierarchical Liquid Crystallinity Combining Colloidal and Molecular Order in Zwitterionic Molecules

Structure/Property Relationships for the Thermotropic Behavior of Lysine-Based Amphiphiles: from Hexagonal to Smectic Phases

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