Evaporation-induced structural evolution of the lamellar mesophase: a time-resolved small-angle X-ray scattering study

2019 ◽  
Vol 52 (5) ◽  
pp. 1169-1175 ◽  
Author(s):  
Jitendra Bahadur ◽  
Avik Das ◽  
Debasis Sen
Keyword(s):  
Structural Evolution ◽  
Water Molecules ◽  
Second Phase ◽  
Lamellar Thickness ◽  
Ambient Conditions ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Head Groups ◽  
Gel Phase

Time-resolved small-angle X-ray scattering (SAXS) measurements have been carried out using the newly developed SAXS beamline at the Indus-2 synchrotron source to study the evaporation-induced structural evolution of the lamellar mesophase. An aqueous dispersion of sodium dodecyl sulfate (SDS) of ∼0.60 volume fraction at room temperature results in a gel phase due to random jamming of the lamellar structured entities. Thermal analysis of SDS in the powder phase shows three distinct phenomena corresponding to evaporation of free and bound water, followed by thermal dissociation of SDS molecules. Time-resolved in situ SAXS measurements during evaporation of the gel under ambient conditions reveal two regimes of structural evolution of the lamellar phase. The evaporation rate in the first phase of evaporation up to 60 min is roughly six times faster than that in the second phase. A plausible mechanism is proposed to explain this behaviour. The intrusion of water molecules into layers sandwiched between polar head groups forms an additional 7 Å thick layer of water molecules, leading to an increase in the distance between the head groups. The evaporation of the water molecules in the first phase up to 60 min causes a reduction in the lamellar thickness of ∼3 Å. Subsequent evaporation of water molecules in the second phase is quite slow owing to the higher binding energy of these water molecules and the low permeability caused by the reduced lamellar thickness after the first phase of evaporation. The swelling behaviour of the lamellar structure under ambient conditions is found to be reversible and the powder-phase structure is observed after a few days of evaporation of the gel phase.

scholarly journals Microscopic identification of the order parameter governing liquid–liquid transition in a molecular liquid

2015 ◽  
Vol 112 (19) ◽  
pp. 5956-5961 ◽  
Author(s):  
Ken-ichiro Murata ◽  
Hajime Tanaka
Keyword(s):  
Order Parameter ◽  
Structural Evolution ◽  
Characteristic Size ◽  
Number Density ◽  
Time Resolved ◽  
X Ray ◽  
Molecular Liquid ◽  
X Ray Scattering ◽  
Liquid Transition ◽  
Scattering Measurements

A liquid–liquid transition (LLT) in a single-component substance is an unconventional phase transition from one liquid to another. LLT has recently attracted considerable attention because of its fundamental importance in our understanding of the liquid state. To access the order parameter governing LLT from a microscopic viewpoint, here we follow the structural evolution during the LLT of an organic molecular liquid, triphenyl phosphite (TPP), by time-resolved small- and wide-angle X-ray scattering measurements. We find that locally favored clusters, whose characteristic size is a few nanometers, are spontaneously formed and their number density monotonically increases during LLT. This strongly suggests that the order parameter of LLT is the number density of locally favored structures and of nonconserved nature. We also show that the locally favored structures are distinct from the crystal structure and these two types of orderings compete with each other. Thus, our study not only experimentally identifies the structural order parameter governing LLT, but also may settle a long-standing debate on the nature of the transition in TPP, i.e., whether the transition is LLT or merely microcrystal formation.

Structural Evolution of Aqueous Zirconium Acetate by Time-Resolved Small-Angle X-ray Scattering and Rheology

2015 ◽  
Vol 119 (22) ◽  
pp. 12660-12667 ◽  
Author(s):  
Martin Bremholm ◽  
Henrik Birkedal ◽  
Bo Brummerstedt Iversen ◽  
Jan Skov Pedersen
Keyword(s):  
Small Angle ◽  
Structural Evolution ◽  
Time Resolved ◽  
X Ray ◽  
Zirconium Acetate ◽  
X Ray Scattering ◽  
Ray Scattering

Time-Resolved Small-Angle X-ray Scattering Study of Reversion Kinetics of δ′ Precipitates in an Al - 12AT.% Li Alloy Utilizing Synchrotron Radiation

1990 ◽  
Vol 205 ◽  
Author(s):  
Haydn Chen ◽  
M.S. Yu ◽  
H. Okuda ◽  
M. Tanaka ◽  
K. Osamura
Keyword(s):  
Synchrotron Radiation ◽  
Small Angle ◽  
Early Stage ◽  
Radius Of Gyration ◽  
Second Phase ◽  
Time Resolved ◽  
X Ray ◽  
Diffuse Interfaces ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractStructure change during the reversion process in an Al−12at.%Li alloy above the metastable δ′ solvus was investigated using a time-resolved small-angle x-ray scattering technique with synchrotron radiation. Results showed that the reversion process started after a short incubation time and that the growth of the stable δ phase began before completion of the δ′ dissolution. The radius of gyration of the second phase particles showed little change in the initial stage of reversion, then increased with time, suggesting the presence of diffuse interfaces between the dissolving δ′ particles and the matrix. It is suggested that the undissolved δ′ particles serve as the nuclei of the more stable δ precipitates, which continue to grow with their radii of gyration showing a parabolic power law in the early stage of growth followed by the familiar coarsening kinetics.

Study of the structural evolution of the 10 Å unstable hydrate of kaolinite during dehydration by XRD and SAXS

2003 ◽  
Vol 36 (3) ◽  
pp. 898-905 ◽  
Author(s):  
S. Naamen ◽  
S. Jemai ◽  
H. Ben Rhaiem ◽  
A. Ben Haj Amara
Keyword(s):  
Structural Evolution ◽  
Second Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Number Of Layers ◽  
Before And After ◽  
Basal Distance ◽  
Clay Layers

This work deals with understanding the structural evolution of the dehydration of the 10 Å unstable hydrate of kaolinite. The method used to characterize this hydrate is based on a comparison between the experimental and the calculated X-ray diffraction profiles. The study was achieved in two steps: (i) the quantitative interpretation of 00lreflections enabled the determination of the number of intercalated water molecules, their positions and the stacking mode of the clay layers along the normal to the (a,b) plane; and (ii) the study of thehklreflections withhand/ork≠ 0 enabled the characterization of the structural evolution in the (a,b) plane of the hydrated kaolinite during dehydration. The hydrate is made up of two demixed phases. The first phase is homogenous and corresponds to a 10 Å hydrated kaolinite, characterized by two H2O molecules per Si2Al2O5(OH)4situated atZ= 7.1 Å from the surface oxygen. Two adjacent layers are translated with respect to each other, withT1= −0.155a+ 0.13b+ 10n. The abundance of this phase decreases during dehydration. The second phase is made up of 10 Å hydrated layers, 8.4 Å hydrated layers and 7.2 Å dehydrated kaolinite layers, randomly interstratified. The abundance of this second phase increases during dehydration. The corresponding interlayer shifts are respectivelyT21= −0.155a+ 0.13b+ 10nfor the 10 Å hydrated layer,T22= −0.355a+ 0.35b+ 8.4nfor the 8.4 Å hydrate andT23= −0.36a− 0.024b+ 7.2nfor the natural kaolinite. In addition to these interlayer shifts, some translation defects are introduced, such as −b/3, which exists in the initial kaolinite. The interpretation of the small-angle X-ray scattering (SAXS) patterns showed that the particle thickness remained the same before and after the hydration treatments, whereas X-ray diffraction (XRD) results indicated that the hydration of kaolinite caused a decrease of the mean number of layers \bar m per crystallite from 40 to 20 layers. This decrease is related to the presence of H2O molecules situated within the micropores in the kaolinite particles that leave their interlayer space after heating at 573 K. The resulting dehydrated compound is characterized by the same basal distance and mean number of layers \bar m per crystallite as for the natural kaolinite, while the proportion of the defects, such as the −b/3 translation, increases in the completely dehydrated compound (45%) compared with the natural kaolinite (10%).

scholarly journals Microfluidics for Time-Resolved Small-Angle X-Ray Scattering

2020 ◽  
Author(s):  
Susanne Seibt ◽  
Timothy Ryan
Keyword(s):  
Self Assembly ◽  
Structural Evolution ◽  
Time Resolved ◽  
X Ray ◽  
Structural Characterisation ◽  
X Ray Scattering ◽  
Saxs Analysis ◽  
Kinetics Of ◽  
Ray Scattering

With the advent of new in situ structural characterisation techniques including X-ray scattering, there has been an increased interest in investigations of the reaction kinetics of nucleation and growth of nanoparticles as well as self-assembly processes. In this chapter, we discuss the applications of microfluidic devices specifically developed for the investigation of time resolved analysis of growth kinetics and structural evolution of nanoparticles and nanofibers. We focus on the design considerations required for spectrometry and SAXS analysis, the advantages of using a combination of SAXS and microfluidics for these measurements, and discuss in an applied fashion the use of these devices for time-resolved research.

Microtubule nucleation sequence studied by time-resolved x-ray scattering and electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 766-767
Author(s):  
Eva-Maria Mandelkow ◽  
Eckhard Mandelkow ◽  
Joan Bordas
Keyword(s):  
Electron Microscopy ◽  
Dynamic Equilibrium ◽  
Time Resolved ◽  
X Ray ◽  
Additional Information ◽  
X Ray Scattering ◽  
Low Concentrations ◽  
Microtubule Growth ◽  
Ray Patterns ◽  
Ray Scattering

When a solution of microtubule protein is changed from non-polymerising to polymerising conditions (e.g. by temperature jump or mixing with GTP) there is a series of structural transitions preceding microtubule growth. These have been detected by time-resolved X-ray scattering using synchrotron radiation, and they may be classified into pre-nucleation and nucleation events. X-ray patterns are good indicators for the average behavior of the particles in solution, but they are difficult to interpret unless additional information on their structure is available. We therefore studied the assembly process by electron microscopy under conditions approaching those of the X-ray experiment. There are two difficulties in the EM approach: One is that the particles important for assembly are usually small and not very regular and therefore tend to be overlooked. Secondly EM specimens require low concentrations which favor disassembly of the particles one wants to observe since there is a dynamic equilibrium between polymers and subunits.

Time-Resolved Cryo-Electron Microscopy of Oscillating Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 502-503
Author(s):  
Eva-Maria Mandelkow ◽  
Ron Milligan
Keyword(s):  
Electron Microscopy ◽  
Dynamic Instability ◽  
Entire Solution ◽  
Reaction Scheme ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
A Chain ◽  
Ray Scattering

Microtubules form part of the cytoskeleton of eukaryotic cells. They are hollow libers of about 25 nm diameter made up of 13 protofilaments, each of which consists of a chain of heterodimers of α-and β-tubulin. Microtubules can be assembled in vitro at 37°C in the presence of GTP which is hydrolyzed during the reaction, and they are disassembled at 4°C. In contrast to most other polymers microtubules show the behavior of “dynamic instability”, i.e. they can switch between phases of growth and phases of shrinkage, even at an overall steady state [1]. In certain conditions an entire solution can be synchronized, leading to autonomous oscillations in the degree of assembly which can be observed by X-ray scattering (Fig. 1), light scattering, or electron microscopy [2-5]. In addition such solutions are capable of generating spontaneous spatial patterns [6].In an earlier study we have analyzed the structure of microtubules and their cold-induced disassembly by cryo-EM [7]. One result was that disassembly takes place by loss of protofilament fragments (tubulin oligomers) which fray apart at the microtubule ends. We also looked at microtubule oscillations by time-resolved X-ray scattering and proposed a reaction scheme [4] which involves a cyclic interconversion of tubulin, microtubules, and oligomers (Fig. 2). The present study was undertaken to answer two questions: (a) What is the nature of the oscillations as seen by time-resolved cryo-EM? (b) Do microtubules disassemble by fraying protofilament fragments during oscillations at 37°C?

In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

2019 ◽  
Author(s):  
Hao Wu ◽  
Jeffrey Ting ◽  
Siqi Meng ◽  
Matthew Tirrell
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Polyelectrolyte Complex ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

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