Small Angle Neutron Scattering Study of Microstructural Transitions in a Surfactant-Based Gel Mesophase

Simmons, Blake A.; Irvin, Glen; Agarwal, Vivek; Bose, Arijit; John, Vijay T.; McPherson, Gary L.; Balsara, Nitash P.

doi:10.1021/la011530r

Cited by 46 publications

(86 citation statements)

References 21 publications

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“…We have extensively studied such a system that consists of bis(2-ethylhexyl) sodium sulfosuccinate, the zwitterionic surfactant l -α-phosphatidylcholine (lecithin), isooctane, and water. The system has similar proportions of water and oil and forms gel-like rigid mesophases with low shear viscosities of up to 10 5 Pa s. The system is optically clear with no phase separation indicating nanostructured water and oil regions 18,21-23. The microstructure of these mesophases has been previously characterized using small-angle neutron scattering (SANS)18,22,23 and nuclear magnetic resonance (NMR) spectroscopy 24,25.…”

Section: Introductionmentioning

confidence: 99%

Cryo-Field Emission Scanning Electron Microscopy Imaging of a Rigid Surfactant Mesophase

Tan

Xu²,

John³

et al. 2008

Langmuir

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The aerosol OT/L-α-phosphatidylcholine/isooctane/water system forms a rigid mesophase that transitions from reverse hexagonal to multilamellar in structure at specific water contents. This study shows that characteristics of ordered liquid-crystalline mesophases can be distinguished and imaged in high clarity using cryo-field emission scanning electron microscopy (cryo-FESEM). The reverse hexagonal phase consists of bundles of long cylinders, some with length scales of over 2 μm, that are randomly oriented as part of a larger domain. Cryo-imaging allows the visualization of the intercylinder spacings and the details of transitions from one domain to another. The multilamellar structured mesophase consists of spherical vesicles of 100 nm to 10 μm in diameter, with intervening noncrystalline isotropic regions. Coexistence regions containing both the reverse hexagonal and lamellar structures are also observed in the transition from the reverse hexagonal to the lamellar phase. These results complement and qualitatively verify our earlier studies with small-angle neutron scattering, high-field nuclear magnetic resonance spectroscopy, and freeze-fracture direct imaging transmission electron microscopy. The information is useful in understanding materials templating in these rigid systems.

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Section: Introductionmentioning

confidence: 99%

Cryo-Field Emission Scanning Electron Microscopy Imaging of a Rigid Surfactant Mesophase

Tan

Xu²,

John³

et al. 2008

Langmuir

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“…Characteristic water channel d spacing for the surfactant template is of the order 10-20 nm as measured by SANS. 4 There is a very approximate reflection of this spacing between the silica nanowires. These silica structures are not altered by solvent extraction of the surfactant or calcinations.…”

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confidence: 98%

“…When this twosurfactant mixture is dissolved in a nonpolar solvent (e.g., isooctane), and water is progressively added, the system evolves from a low viscosity solution to a gellike state with crystalline order illustrated through small-angle neutron scattering measurements. 4 For example, over the composition range surfactant/isooctane/water 0.27/0.27/0.46 to 0.21/0.21/0.57 (in weight fractions), the surfactant mesophase has columnar hexagonal symmetry, with water cylindrical columns arranged in hexagonal geometry (the H II phase). 4 The system is optically clear, has a high viscosity up to 10 6 Pa‚s at low shear rates, and has a relatively high rigidity as characterized by a storage modulus (G′) of 10 4 Pa. Figure 1 illustrates small-angle neutron scattering patterns for the surfactant mesophase where D 2 O has been used instead of water to provide sufficient contrast.…”

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confidence: 99%

“…4 For example, over the composition range surfactant/isooctane/water 0.27/0.27/0.46 to 0.21/0.21/0.57 (in weight fractions), the surfactant mesophase has columnar hexagonal symmetry, with water cylindrical columns arranged in hexagonal geometry (the H II phase). 4 The system is optically clear, has a high viscosity up to 10 6 Pa‚s at low shear rates, and has a relatively high rigidity as characterized by a storage modulus (G′) of 10 4 Pa. Figure 1 illustrates small-angle neutron scattering patterns for the surfactant mesophase where D 2 O has been used instead of water to provide sufficient contrast. It shows scattering profiles obtained in a Couette cell, providing information in both the flow-vorticity (radial) and the flow gradient-vorticity (tangential) planes.…”

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confidence: 99%

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Shear-Induced Alignment and Nanowire Silica Synthesis in a Rigid Crystalline Surfactant Mesophase

et al. 2004

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Highly aligned stringlike silica nanostructures are obtained through templated synthesis in the columnar hexagonal structure of a rigid crystalline surfactant mesophase. A two-step procedure is used to first shear-align the surfactant mesophase and then conduct synthesis under quiescent conditions in the mesophase. The mesophase retains its alignment for extended periods, allowing materials synthesis to be decoupled from the application of shear. The observations have significant implications in the control of ceramic microstructure morphology and transitions from nonaligned to aligned nanowire type structures.

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“…SANS data in the high q-region was described by a signature broad-peak, a profile normally noticed in scattering from amorphous soft materials. In this formalism, the typical distance between scattering heterogeneities is explained by d-spacing, d 0 which is the peak position of the broad correlation peak located at q 0 .Theq 0 value signifies the peak position of different morphologies such as in lamellar, cylindrical, spherical or for bi-continuous structures [29]. Here in the case of hydrogels one can see the significance of such a model.…”

Section: Static Structure Factormentioning

confidence: 99%

Structural Hierarchy in DNA Hydrogels

Pandey

Rawat

et al. 2017

JABB

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Sol-gel transition in aqueous DNA solutions was probed to determine the gelation time t gel and temperature T gel . It was remarkable to observe that T gel linearly increased from 36 to 57°C and t gel decreased from 700 to 350 s with increase in DNA concentration. The hydrogels were studied by using small angle neutron scattering (SANS) ([DNA]≤ 3 %(w/v)) to determine the underlying hierarchy of length scales. From structure factor profile analysis, three distinct signatures were obtained:a. Radius of gyration R g ≈ 40±3nm, which assigned a length of 140 nm to DNA strand b. Geometry of scattering moiety defined by the value of α ≈ 2.2±0.1 indicating Gaussian chain behavior c. Correlation length, ξ increased from 0.50 to 3.30nm and the inter-chain spacing d 0 decreased from 15.6 to 9.8nm, with increase in DNA concentration.Physical networks were formed for concentration, c*≥ 2% (w/v) and the system involved at least five identifiable length scales. A revisit has shown that hierarchical structure of DNA hydrogel owes its origin to considerable self-organization at the molecular level dependent on biopolymer concentration.

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Small Angle Neutron Scattering Study of Microstructural Transitions in a Surfactant-Based Gel Mesophase

Cited by 46 publications

References 21 publications

Cryo-Field Emission Scanning Electron Microscopy Imaging of a Rigid Surfactant Mesophase

Cryo-Field Emission Scanning Electron Microscopy Imaging of a Rigid Surfactant Mesophase

Shear-Induced Alignment and Nanowire Silica Synthesis in a Rigid Crystalline Surfactant Mesophase

Structural Hierarchy in DNA Hydrogels

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