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.

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 Liquid Crystal Ordering in the Hexagonal Phase of Rod-Coil Diblock Copolymers

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1262
Author(s):  
Mikhail A. Osipov ◽  
Maxim V. Gorkunov ◽  
Alexander A. Antonov
Keyword(s):  
Liquid Crystal ◽  
Order Parameter ◽  
Density Functional ◽  
Diblock Copolymers ◽  
Microphase Separation ◽  
Hexagonal Phase ◽  
Orientational Order ◽  
Order Parameters ◽  
Copolymer Composition ◽  
Rigid Rod

Density functional theory of rod-coil diblock copolymers, developed recently by the authors, has been generalised and used to study the liquid crystal ordering and microphase separation effects in the hexagonal, lamellar and nematic phases. The translational order parameters of rod and coil monomers and the orientational order parameters of rod-like fragments of the copolymer chains have been determined numerically by direct minimization of the free energy. The phase diagram has been derived containing the isotropic, the lamellar and the hexagonal phases which is consistent with typical experimental data. The order parameter profiles as functions of temperature and the copolymer composition have also been determined in different anisotropic phases. Finally, the spatial distributions of the density of rigid rod fragments and of the corresponding orientational order parameter in the hexagonal phase have been calculated.

A Comparative Experimental and Theoretical Study between Heteroarm Star and Diblock Copolymers in the Microphase Separated State

2000 ◽  
Vol 33 (17) ◽  
pp. 6330-6339 ◽  
Author(s):  
Valérie Grayer ◽  
Elena E. Dormidontova ◽  
Georges Hadziioannou ◽  
Constantinos Tsitsilianis
Keyword(s):  
Diblock Copolymers ◽  
Theoretical Study

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

scholarly journals Phase Behavior of Melts of Diblock-Copolymers with One Charged Block

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1027 ◽  
Author(s):  
Alexey A. Gavrilov ◽  
Alexander V. Chertovich ◽  
Igor I. Potemkin
Keyword(s):  
Phase Diagram ◽  
Phase Behavior ◽  
Electrostatic Interactions ◽  
Diblock Copolymers ◽  
Volume Fraction ◽  
Microphase Separation ◽  
Dissipative Particle Dynamics ◽  
Homogeneous Structure ◽  
Electrostatic Energy ◽  
Ordered Structures

In this work, we investigated the phase behavior of melts of block-copolymers with one charged block by means of dissipative particle dynamics with explicit electrostatic interactions. We assumed that all the Flory–Huggins χ parameters were equal to 0. We showed that the charge- correlation attraction solely can cause microphase separation with a long-range order; a phase diagram was constructed by varying the volume fraction of the uncharged block and the electrostatic interaction parameter λ (dimensionless Bjerrum length). The obtained phase diagram was compared to the phase diagram of “equivalent” neutral diblock-copolymers with the non-zero χ-parameter between the beads of different blocks. The neutral copolymers were constructed by grafting the counterions to the corresponding co-ions of the charged block with further switching off the electrostatic interactions. Surprisingly, the differences between these phase diagrams are rather subtle; the same phases in the same order are observed, and the positions of the order-disorder transition ODT points are similar if the λ-parameter is considered as an “effective” χ-parameter. Next, we studied the position of the ODT for lamellar structure depending on the chain length N. It turned out that while for the uncharged diblock copolymer the product χcrN was almost independent of N, for the diblock copolymers with one charged block we observed a significant increase in λcrN upon increasing N. This can be attributed to the fact that the counterion entropy prevents the formation of ordered structures, and its influence is more pronounced for longer chains since they undergo the transition to ordered structures at smaller values of λ, when the electrostatic energy becomes comparable to kbT. This was supported by studying the ODT in diblock-copolymers with charged blocks and counterions cross-linked to the charged monomer units. The ODT for such systems was observed at significantly lower values of λ, with the difference being more pronounced at longer chain lengths N. The fact that the microphase separation is observed even at zero Flory–Huggins parameter can be used for the creation of “high-χ” copolymers: The incorporation of charged groups (for example, ionic liquids) can significantly increase the segregation strength. The diffusion of counterions in the obtained ordered structures was studied and compared to the case of a system with the same number of charged groups but a homogeneous structure; the diffusion coefficient along the lamellar plane was found to be higher than in any direction in the homogeneous structure.

Ordered packing arrangements of spherical micelles of diblock copolymers in two and three dimensions

1987 ◽  
Vol 20 (11) ◽  
pp. 2934-2939 ◽  
Author(s):  
Edwin L. Thomas ◽  
David J. Kinning ◽  
David B. Alward ◽  
Chris S. Henkee
Keyword(s):  
Diblock Copolymers ◽  
Three Dimensions ◽  
Spherical Micelles

scholarly journals Theoretical Study on the Formation of Spherical Micelles

1991 ◽  
Vol 64 (2) ◽  
pp. 682-684 ◽  
Author(s):  
Noriaki Funasaki ◽  
Sakae Hada
Keyword(s):  
Theoretical Study ◽  
Spherical Micelles

Crystallization-driven one-dimensional self-assembly of polyethylene-b-poly(tert-butylacrylate) diblock copolymers in DMF: effects of crystallization temperature and the corona-forming block

Soft Matter ◽  
2016 ◽  
Vol 12 (1) ◽  
pp. 67-76 ◽  
Author(s):  
Bin Fan ◽  
Lei Liu ◽  
Jun-Huan Li ◽  
Xi-Xian Ke ◽  
Jun-Ting Xu ◽  
...  
Keyword(s):  
Crystallization Temperature ◽  
Self Assembly ◽  
Diblock Copolymers ◽  
Block Length ◽  
One Dimensional ◽  
Cylindrical Micelles

Crystallization temperature and the PtBA block length affect the growth of crystalline PE-b-PtBA cylindrical micelles, and quasi-living growth can be achieved.

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