Related Experiment Video
Updated: Aug 4, 2026
06:44
From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Solid State Transitions of Asymmetric Catanionic Surfactants
Tomasic1, Popovic, Filipovic-Vincekovic
1Chemistry Department, Ruder Boskovic Institute
Journal of Colloid and Interface Science
|July 27, 1999
Summary
Asymmetric catanionic surfactants show complex phase behavior and thermal properties. Tail asymmetry influences polymorphism and lamellar thickness in these novel surfactant systems.
Area of Science:
- Materials Science
- Physical Chemistry
- Supramolecular Chemistry
Background:
- Catanionic surfactants, formed from oppositely charged surfactant molecules, offer unique self-assembly properties.
- Investigating the impact of structural asymmetry in catanionic surfactants is crucial for understanding their phase behavior.
Purpose of the Study:
- To synthesize asymmetric catanionic surfactants by combining hexadecyltrimethylammonium bromide with sodium alkyl sulfates of varying chain lengths (C10, C12, C14).
- To elucidate the influence of alkyl chain asymmetry on the thermal properties, polymorphism, and mesomorphism of these surfactants.
Main Methods:
- Polarizing microscopy for textural analysis of liquid crystalline phases.
- Differential scanning calorimetry (DSC) for detecting phase transitions and thermal events.
- X-ray diffraction (XRD) for structural characterization of crystalline and liquid crystalline phases.
Main Results:
- Asymmetric catanionic surfactants displayed complex polymorphism and thermotropic mesomorphism, transitioning from crystalline solids to isotropic liquids upon heating.
- Observed successive phase transitions including solid-solid crystalline, solid crystalline-liquid crystalline, and liquid crystalline-isotropic liquid.
- The number of observed polymorphs was directly related to the degree of asymmetry in surfactant tail lengths.
- Lamellar thickness increased linearly with alkyl sulfate chain length and with increasing temperature.
- Polarizing microscopy confirmed the presence of smectic phases with characteristic textures.
Conclusions:
- Alkyl chain asymmetry is a key factor governing the complex phase behavior and polymorphism of catanionic surfactants.
- The observed thermal transitions and structural variations highlight the tunable nature of these asymmetric surfactant systems.
- These findings contribute to the fundamental understanding of self-assembly in complex surfactant mixtures.
Related Concept Videos
03:13Intermolecular Forces
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...
02:54Molecular and Ionic Solids
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions.
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
00:57Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...
01:27Surface Active Agents
Surfactants, named for their behavior at interfaces, positively adsorb at the interfaces of two phases, reducing interfacial tension. Their versatility as emulsifiers, detergents, and foaming agents stems from this ability. Surfactants, often termed amphiphiles, share the property of amphipathy, with molecules having both hydrophilic and hydrophobic portions. The hydrophilic part is called the head, and the hydrophobic part, including an elongated alkyl substituent, forms the tail.Surfactants...
01:30Micelles
Micelle formation is an intricate process that hinges on the properties of amphiphilic or amphipathic molecules and the conditions of the system in which they are found. Amphiphilic molecules, which have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, play a critical role in this process.In aqueous environments, these molecules arrange themselves such that their hydrophilic heads are turned towards the water phase, while their hydrophobic tails are oriented away...