scholarly journals Fusion and clustering of spherical micelles by extruding through a cylindrical channel

RSC Advances ◽  
2019 ◽  
Vol 9 (42) ◽  
pp. 24394-24400
Author(s):  
Manman Chen ◽  
Xinghua Zhang ◽  
Hui Zhang
Keyword(s):  
Cylindrical Channel ◽  
Cylindrical Micelles ◽  
Spherical Micelles

Experiments have shown that worm-like cylindrical micelles can be obtained by extruding spherical micelles through a cylindrical channel.

Structure and Dynamics of Spherical and Rodlike Alkyl Ethoxylate Surfactant Micelles Investigated Using NMR Relaxation and Atomistic Molecular Dynamics Simulations

2019 ◽  
Author(s):  
Allison Edwards ◽  
Abdolreza Javidialesaadi ◽  
Katie Weigandt ◽  
George Stan ◽  
Charles Eads
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Nmr Relaxation ◽  
Cross Relaxation ◽  
Relaxation Rates ◽  
Surfactant Micelles ◽  
Cylindrical Micelles ◽  
Spherical Micelles ◽  
Dynamics Simulations ◽  
Relative Motions

We study molecular arrangements and dynamics in alkyl ethoxylate nonionic surfactant micelles by combining high field (600 and 700 MHz) NMR relaxation measurements with large-scale atomistic molecular dynamics simulations. For spherical micelles, but not for cylindrical micelles, cross relaxation rates are positive only for surfactant alkyl tail atoms connected to the hydrophilic head group. All cross relaxation rates are negative for cylindrical micelles. This effect is reproducible either by changing composition (ratios of the nonionic surfactants) or changing temperature of a single surfactant in order to change the micelle shape. We validate the micelle shape by SANS and use the results as a guide for our simulations. We calculate parameters that determine relaxation rates directly from simulated trajectories, without introducing specific functional forms. Results indicate that relative motions of nearby atoms are liquid-like, in agreement with 13C T1 measurements, though constrained by micelle morphology. Relative motions of distant atoms have slower components because the relative changes in distances and angles are smaller when the moving atoms are further apart. The slow, long-range motions appear to be responsible for the predominantly negative cross relaxation rates observed in NOESY spectra. The densities of atoms from positions 1 and 2 in the boundary region are lower in spherical micelles compared to cylindrical micelles. Correspondingly, motions in this region are less constrained by micelle morphology in the spherical compared to the cylindrical cases. The two effects of morphology lead to the unusual occurrence of positive cross relaxation involving positions 1 and 2 for spheres.

Mechanism for Transition of Reverse Cylindrical Micelles to Spherical Micelles Induced by Diverse Alcohols

Langmuir ◽  
2020 ◽  
Vol 36 (28) ◽  
pp. 8174-8183
Author(s):  
Hwa-Jin Lee ◽  
Hyun-Jin Kim ◽  
Da-Gyun Park ◽  
Kyeong Sik Jin ◽  
Ji Woong Chang ◽  
...  
Keyword(s):  
Cylindrical Micelles ◽  
Spherical Micelles

Structure and Dynamics of Spherical and Rodlike Alkyl Ethoxylate Surfactant Micelles Investigated Using NMR Relaxation and Atomistic Molecular Dynamics Simulations

2019 ◽  
Author(s):  
Allison Edwards ◽  
Abdolreza Javidialesaadi ◽  
Katie Weigandt ◽  
George Stan ◽  
Charles Eads
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Nmr Relaxation ◽  
Cross Relaxation ◽  
Relaxation Rates ◽  
Surfactant Micelles ◽  
Cylindrical Micelles ◽  
Spherical Micelles ◽  
Dynamics Simulations ◽  
Relative Motions

We study molecular arrangements and dynamics in alkyl ethoxylate nonionic surfactant micelles by combining high field (600 and 700 MHz) NMR relaxation measurements with large-scale atomistic molecular dynamics simulations. For spherical micelles, but not for cylindrical micelles, cross relaxation rates are positive only for surfactant alkyl tail atoms connected to the hydrophilic head group. All cross relaxation rates are negative for cylindrical micelles. This effect is reproducible either by changing composition (ratios of the nonionic surfactants) or changing temperature of a single surfactant in order to change the micelle shape. We validate the micelle shape by SANS and use the results as a guide for our simulations. We calculate parameters that determine relaxation rates directly from simulated trajectories, without introducing specific functional forms. Results indicate that relative motions of nearby atoms are liquid-like, in agreement with 13C T1 measurements, though constrained by micelle morphology. Relative motions of distant atoms have slower components because the relative changes in distances and angles are smaller when the moving atoms are further apart. The slow, long-range motions appear to be responsible for the predominantly negative cross relaxation rates observed in NOESY spectra. The densities of atoms from positions 1 and 2 in the boundary region are lower in spherical micelles compared to cylindrical micelles. Correspondingly, motions in this region are less constrained by micelle morphology in the spherical compared to the cylindrical cases. The two effects of morphology lead to the unusual occurrence of positive cross relaxation involving positions 1 and 2 for spheres.

scholarly journals Computational Investigations of a pH-Induced Structural Transition in a CTAB Solution with Toluic Acid

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6978
Author(s):  
Tingyi Wang ◽  
Hui Yan ◽  
Li Lv ◽  
Yingbiao Xu ◽  
Lingyu Zhang ◽  
...  
Keyword(s):  
Electrostatic Interactions ◽  
Carboxyl Groups ◽  
Electrostatic Repulsion ◽  
Structural Transitions ◽  
Density Distributions ◽  
Cylindrical Micelles ◽  
Spherical Micelles ◽  
Aqueous Surfactants ◽  
Dynamics Simulations ◽  
Almost All

In this work, molecular dynamics simulations were performed to study the pH-induced structural transitions for a CTAB/p-toluic acid solution. Spherical and cylindrical micelles were obtained for aqueous surfactants at pH 2 and 7, respectively, which agrees well with the experimental observations. The structural properties of two different micelles were analyzed through the density distributions of components and the molecular orientations of CTA+ and toluic acid inside the micelles. It was found that the bonding interactions between CTA+ and toluic in spherical and cylindrical micelles are very different. Almost all the ionized toluic acid (PTA−) in the solution at pH 7 was solubilized into the micelles, and it was located in the CTA+ headgroups region. Additionally, the bonding between surfactant CTA+ and PTA− was very tight due to the electrostatic interactions. The PTA− that penetrated into the micelles effectively screened the electrostatic repulsion among the cationic headgroups, which is considered to be crucial for maintaining the cylindrical micellar shape. As the pH decreased, the carboxyl groups were protonated. The hydration ability of neutral carboxyl groups weakened, resulting in deeper penetration into the micelles. Meanwhile, their bonding interactions with surfactant headgroups also weakened. Accompanied by the strengthen of electrostatic repulsion among the positive headgroups, the cylindrical micelle was broken into spherical micelles. Our work provided an atomic-level insights into the mechanism of pH-induced structural transitions of a CTAB/p-toluic solution, which is expected to be useful for further understanding the aggregate behavior of mixed cationic surfactants and aromatic acids.

pH- and concentration-controlled self-assembly of spherical micelles with cavity, necklace and cylindrical micelles

RSC Advances ◽  
2016 ◽  
Vol 6 (52) ◽  
pp. 47174-47177
Author(s):  
Rui Qi ◽  
Yong Jin
Keyword(s):  
Hydrogen Bonding ◽  
Diblock Copolymer ◽  
Self Assembly ◽  
Cylindrical Micelles ◽  
Spherical Micelles

A novel diblock copolymer with one block composed of hydrophobic motifs, hydrogen-bonding carbamates and pH-triggered carboxy groups was developed, which could self-assemble into spherical micelles with cavity, necklaces and cylindrical micelles.

Cryo-TEM of CTAB micelles and microemulsions

1988 ◽  
Vol 46 ◽  
pp. 112-113
Author(s):  
Phillip K. Vinson
Keyword(s):  
Mean Curvature ◽  
Surfactant Concentration ◽  
Phase Region ◽  
Water Soluble ◽  
Ionic Surfactants ◽  
Electrostatic Repulsion ◽  
Micellar Aggregates ◽  
Head Groups ◽  
Cylindrical Micelles ◽  
Spherical Micelles

Single-tailed surfactant molecules in aqueous solutions can associate into several different microstructural forms within a one-phase region of the phase diagram (Fig. 1). The molecules associate into globular aggregates called spherical micelles above a surfactant concentration called the critical micelle concentration, or cmc. At higher surfactant concentrations some surfactants will associate into rod-like micelles called cylindrical micelles. In systems containing ionic surfactants the transition from spherical to cylindrical micelles can be brought about at lower surfactant concentrations by adding an electrolyte. The electrolyte screens the electrostatic repulsion between surfactant head groups and allows formation of the lower mean curvature cylindrical microstructures. Micellar aggregates are equilibrium microstructures in which the nonpolar (often hydrocarbon or fluorocarbon) moieties of the surfactant molecules are shielded from the aqueous medium by the water-soluble moieties of the surfactant molecules. The solubilization of oil into the nonpolar micelle interior produces an aqueous solution of oil swollen micelles, i.e., a microemulsion.

Cylindrical Micelles in Rigid-Flexible Diblock Copolymers

1991 ◽  
Vol 248 ◽  
Author(s):  
D.R.M Williams ◽  
G.H. Fredrickson
Keyword(s):  
Phase Diagram ◽  
Diblock Copolymers ◽  
Theoretical Study ◽  
Flexible Tail ◽  
Cylindrical Micelles ◽  
Rigid Rod ◽  
Spherical Micelles

AbstractWe present a theoretical study of a melt of diblock copolymers consisting of a rigid rod and a flexible tail. It is shown that in addition to the lamellax phases previously discussed, there also exist phases of “hockey puck” micelles, where the rods are packed axially into cylinders. These phases occupy most of the phase diagram previously thought to consist of monolayer lamellae. It is argued that spherical micelles probably do not exist.

A new Guinier–Porod model

2010 ◽  
Vol 43 (4) ◽  
pp. 716-719 ◽  
Author(s):  
Boualem Hammouda
Keyword(s):  
Empirical Model ◽  
Small Angle ◽  
Small Angle Scattering ◽  
Radius Of Gyration ◽  
Single Model ◽  
New Model ◽  
Angle Scattering ◽  
Cylindrical Micelles ◽  
Standard Linear ◽  
Spherical Micelles

Small-angle scattering (SAS) curves are characterized by two main features: the Guinier region and the Porod region. Standard linear plots are available to fit SAS data and obtain a radius of gyration and a Porod exponent. A new Guinier–Porod empirical model is introduced to fit SAS data from spherical as well as nonspherical objects such as rods or platelets. It also applies to shapes intermediate between spheres and rods or between rods and platelets. The new model is used to fit SAS data from a Pluronic solution that sequentially forms unimers, then spherical micelles, then cylindrical micelles, then lamellar micelles upon heating. This single model can fit structures associated with all four phases as well as the intermediate structures.

New Structure of CTAB Templated Silica Films as revealed by GISAXS coupled to HRTEM

2000 ◽  
Vol 628 ◽  
Author(s):  
Sophie Besson ◽  
Catherine Jacquiod ◽  
Thierry Gacoin ◽  
André Naudon ◽  
Christian Ricolleau ◽  
...  
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Grazing Incidence ◽  
Hexagonal Structure ◽  
X Ray Diffraction ◽  
Electronic Microscopy ◽  
Silica Films ◽  
X Ray ◽  
X Ray Scattering ◽  
Hexagonal Arrangement ◽  
Spherical Micelles

ABSTRACTA microstructural study on surfactant templated silica films is performed by coupling traditional X-Ray Diffraction (XRD) and Transmission Electronic Microscopy (TEM) to Grazing Incidence Small Angle X-Ray Scattering (GISAXS). By this method it is shown that spin-coating of silicate solutions with cationic surfactant cetyltrimethylammonium bromide (CTAB) as a templating agent provides 3D hexagonal structure (space group P63/mmc) that is no longer compatible with the often described hexagonal arrangement of tubular micelles but rather with an hexagonal arrangement of spherical micelles. The extent of the hexagonal ordering and the texture can be optimized in films by varying the composition of the solution.

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