Styrene/butadiene block copolymer micelles in heptane

1985 ◽  
Vol 63 (1) ◽  
pp. 249-252 ◽  
Author(s):  
T. L. Bluhm ◽  
M. D. Whitmore
Keyword(s):  
Block Copolymer ◽  
Radius Of Gyration ◽  
X Ray ◽  
X Ray Scattering ◽  
Micelle Core ◽  
Theoretical Predictions ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Styrene Butadiene ◽  
Good Agreement

The radius of gyration of poly(styrene-b-butadiene) block copolymer micelles in n-heptane is measured by small angle X-ray scattering (SAXS). The results are compared with theoretical predictions, and good agreement is found, particularly for the appropriate scaling relations. It is argued that the radius of gyration of the micelles depends on both the molecular weight and the composition of the copolymers. The dominant factors which determine the micelle core and corona dimensions are identified.

The Morphology of Block Copolymer Micelles in Supercritical Carbon Dioxide by Small-Angle Neutron and X-ray Scattering

1997 ◽  
Vol 30 (5) ◽  
pp. 690-695 ◽  
Author(s):  
J. D. Londono ◽  
R. Dharmapurikar ◽  
H. D. Cochran ◽  
G. D. Wignall ◽  
J. B. McClain ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Block Copolymer ◽  
Small Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Environmentally Responsible ◽  
Theoretical Predictions ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Ray Scattering

Above its critical point, carbon dioxide forms a super-critical fluid, which promises to be an environmentally responsible replacement for the organic solvents traditionally used in polymerizations. Many lipophilic polymers such as polystyrene (PS) are insoluble in CO2, though polymerizations may be accomplished via the use of PS-fluoropolymer stabilizers, which act as emulsifying agents. Small-angle neutron and X-ray scattering have been used to show that these molecules form micelles with a CO2-phobic PS core and a CO2-philic fluoropolymer corona. When the PS block was fixed in length and the fluorinated corona block was varied, the number of block copolymer molecules per micelle (six to seven) remained constant. Thus, the coronal block molecular weight exerts negligible influence on the aggregation number, in accordance with the theoretical predictions of Halperin, Tirrell & Lodge [Adv. Polym. Sci. (1992), 100, 31–46]. These observations are relevant to understanding the mechanisms of micellization and solubilization in supercritical fluids.

scholarly journals Structure of PEP–PEO block copolymer micelles: exploiting the complementarity of small-angle X-ray scattering and static light scattering

2011 ◽  
Vol 44 (3) ◽  
pp. 473-482 ◽  
Author(s):  
Grethe Vestergaard Jensen ◽  
Qing Shi ◽  
María J. Hernansanz ◽  
Cristiano L. P. Oliveira ◽  
G. Roshan Deen ◽  
...  
Keyword(s):  
Light Scattering ◽  
Block Copolymer ◽  
Small Angle ◽  
Static Light Scattering ◽  
Length Scales ◽  
X Ray ◽  
X Ray Scattering ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Poly Ethylene

The structure of large block copolymer micelles is traditionally determined by small-angle neutron scattering (SANS), covering a large range of scattering vectors and employing contrast variation to determine the overall micelle morphology as well as the internal structure on shorter length scales. The present work shows that the same information can be obtained by combining static light scattering (SLS) and small-angle X-ray scattering (SAXS), which provide information on, respectively, large and short length scales. Micelles of a series of block copolymers of poly(ethylene propylene)-b-poly(ethylene oxide) (PEP–PEO) in a 70% ethanol solution are investigated. The polymers have identical PEP blocks of 5.0 kDa and varying PEO blocks of 2.8–49 kDa. The SLS contrasts of PEP and PEO are similar, providing a homogeneous contrast, making SLS ideal for determining the overall micelle morphology. The SAXS contrasts of the two components are very different, allowing for resolution of the internal micelle structure. A core–shell model with a PEP core and PEO corona is fitted simultaneously to the SAXS and SLS data using the different contrasts of the two blocks for each technique. With increasing PEO molecular weight, a transition from cylindrical to spherical micelles is observed. This transition cannot be identified from the SAXS data alone, but only from the SLS data.

Liquid Crystalline Phase Behavior of Well-Defined Cylindrical Block Copolymer Micelles Using Synchrotron Small-Angle X-ray Scattering

2015 ◽  
Vol 48 (5) ◽  
pp. 1579-1591 ◽  
Author(s):  
Dominic W. Hayward ◽  
Joe B. Gilroy ◽  
Paul A. Rupar ◽  
Laurent Chabanne ◽  
Claire Pizzey ◽  
...  
Keyword(s):  
Block Copolymer ◽  
Phase Behavior ◽  
Small Angle ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
X Ray ◽  
X Ray Scattering ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Cylindrical Block

Structural Analysis of Bottlebrush Block Copolymer Micelles Using Small-Angle X-ray Scattering

2020 ◽  
Vol 9 (9) ◽  
pp. 1261-1266
Author(s):  
Seyoung Kim ◽  
Yunshik Cho ◽  
Jee Hyun Kim ◽  
Sanghoon Song ◽  
Jeewoo Lim ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Block Copolymer ◽  
Small Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Ray Scattering

Study of Sedimentation Velocity of Block Copolymer Micelles

1993 ◽  
Vol 58 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Minmin Tian ◽  
C. Ramireddy ◽  
Stephen E. Webber ◽  
Petr Munk
Keyword(s):  
Block Copolymer ◽  
Methacrylic Acid ◽  
Mixed Solvent ◽  
Hard Spheres ◽  
Sedimentation Velocity ◽  
Hydrodynamic Coefficient ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Size Heterogeneity ◽  
Good Agreement

No anomalies were observed during the measurement of sedimentation coefficients of block copolymer micelles formed by copolymers of styrene and methacrylic acid in a mixed solvent; 80 vol.% of dioxane and 20 vol.% of water. The shapes of the sedimenting boundaries suggest that the size heterogeneity of the micelles is small. Linear relations between 1/s and c were obtained. The value of the hydrodynamic coefficient κ was between 2 and 4 in a good agreement with the value 2.75 or 2.86 that was obtained by combining Burgers' or Fixman's values of the coefficient of the concentration dependence kvs for hard spheres with Einstein's value of [η] for spheres.

Synthesis of Shell Cross-Linked Block Copolymer Micelles with Poly(p-styrenesulfonic acid) in the Micelle Core

2005 ◽  
Vol 38 (24) ◽  
pp. 9957-9962 ◽  
Author(s):  
Kozo Matsumoto ◽  
Tetsuo Hirabayashi ◽  
Tamotsu Harada ◽  
Hideki Matsuoka
Keyword(s):  
Block Copolymer ◽  
Micelle Core ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles

Dynamics of Block Copolymer Micelles Revealed by X-Ray Intensity Fluctuation Spectroscopy

1997 ◽  
Vol 78 (7) ◽  
pp. 1275-1278 ◽  
Author(s):  
S. G. J. Mochrie ◽  
A. M. Mayes ◽  
A. R. Sandy ◽  
M. Sutton ◽  
S. Brauer ◽  
...  
Keyword(s):  
Block Copolymer ◽  
Intensity Fluctuation ◽  
X Ray ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles

scholarly journals Structural comparisons of the native and reactive-centre-cleaved forms of α1-antitrypsin by neutron- and X-ray-scattering in solution

1990 ◽  
Vol 267 (1) ◽  
pp. 203-212 ◽  
Author(s):  
K F Smith ◽  
R A Harrison ◽  
S J Perkins
Keyword(s):  
Conformational Changes ◽  
Potassium Phosphate ◽  
Radius Of Gyration ◽  
Neutron Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Alpha 1 Antitrypsin ◽  
Internal Inhomogeneity ◽  
Good Agreement ◽  
Ray Scattering

alpha 1-Antitrypsin is the best-characterized member of the serpin (serine-proteinase inhibitor) superfamily. Its solution structure was studied by high-flux neutron-scattering and synchrotron X-ray-scattering. Neutron data show that its absorption coefficient A1% 280,1cm is 5.4. The neutron radius of gyration RG at infinite contrast for native alpha 1-antitrypsin is 2.61 nm, characteristic of a moderately elongated structure, and its cross-sectional RG is 1.34 nm. The internal inhomogeneity of scattering densities within alpha 1-antitrypsin is high at 29 x 10(-5). The X-ray RG is 2.91 nm, in good agreement with the neutron RG of 2.82 nm in 1H2O. This RG is unchanged in reactive-centre-cleaved alpha 1-antitrypsin. These parameters are also unchanged at pH 8 in sodium/potassium phosphate buffers up to 0.6 M. The neutron and X-ray curves for native alpha 1-antitrypsin were compared with Debye simulation based on the crystal structure of reactive-centre-cleaved (papain) alpha 1-antitrypsin. After allowance for residues not visible in the crystallographic electron-density map, and rejoining the proteolysed site between Met-358 and Ser-359 by means of a relatively minor conformational re-arrangement, good agreement to a structural resolution of 4 nm is obtained with the neutron data in two contrasts and with the X-ray data. The structures of the native and cleaved forms of alpha 1-antitrypsin are thus similar within the resolution of solution scattering. This places an upper limit on the magnitude of the presumed conformational changes that occur in alpha 1-antitrypsin on reactive-centre cleavage, as indicated in earlier spectroscopic investigations of the Met-358-Ser-359 peptide-bond cleavage. Methods for scattering-curve simulations from crystal structures are critically assessed. The RG data lead to dimensions of 7.8 nm x 4.9 nm x 2.2 nm for native alpha 1-antitrypsin. The high internal inhomogeneity and the asymmetric shorter semi-axes of 4.9 nm and 2.2 nm suggest that the three oligosaccharide chains of alpha 1-antitrypsin are essentially freely extended into solvent in physiological conditions. This conclusion is also supported by the Debye simulations, and by modelling based on hydrodynamic parameters.

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