WAXD Research Articles

Quantitative Analysis of Salt-Induced RNA Duplex Variations by Wide-Angle X-ray Scattering (WAXS)

The recognized biological functions of the RNA duplex are coupled to its structure, which is often assumed to be an A-form conformation. However, recent folding studies suggest that salt-induced conformational variations of the RNA duplex may need to be considered in determining RNA folding models. Here, we describe the application of wide-angle x-ray scattering (WAXS) to capture variations in duplex structure. When coupled with models from molecular dynamics (MD) simulations, these variations can be quantified to identify key structural parameters of the duplex. The results of this analysis were tested by 5-fold cross-validation and the effects of experimental errors were investigated by applying our analysis framework to noisy data. Our analysis reveals that the RNA duplex deviates significantly from the A-form conformation and allows a quantification of these differences. Most importantly, the addition of Mg ions tightens the RNA duplex by unwinding it and shrinking the groove widths. Such changing duplex structures must be accounted for when constructing models of divalent ion induced RNA folding.

In-situ analysis of continuous cooling precipitation in Al alloys by wide-angle X-ray scattering

ABSTRACT The aim of this work is to investigate quench induced precipitation during continuous cooling in aluminium wrought alloys EN AW-7150 and EN AW-6082 using in situ synchrotron wide-angle X-ray scattering (WAXS). While X-ray diffraction is usually an ex situ method, a variety of diffraction patterns were recorded during the cooling process, allowing in situ analysis of the precipitation process. The high beam energy of about 100 keV allows the beam to penetrate a bulk sample with a 4 mm diameter in a quenching dilatometer. Additionally, the high intensity of a synchrotron source enables sufficiently high time resolution for fast in situ cooling experiments. Reaction peaks could be detected and compared with results from differential scanning calorimetry (DSC) by this method. A methodology is presented in this paper to evaluate WAXS data in a way that is directly comparable to DSC-experiments. The results show a high correlation between both techniques, DSC and WAXS, and can significantly improve continuous cooling precipitation diagrams.

Substitution degree and fatty chain length influence on structure and properties of fatty acid cellulose esters

A series of fatty acid cellulose esters (FACEs) with both various degrees of substitution (from DS = 1.7 to 3) and side chain length were obtained by grafting aliphatic acid chlorides (from C10 to C16) onto cellulose backbone, in a homogeneous LiCl/DMAc medium. These materials were characterized by Fourier Transformed InfraRed (FTIR) and Nuclear Magnetic Resonance of Proton (1H NMR) spectroscopies, as well as Wide Angle X-ray Scattering (WAXS), Differential Scanning Calorimetry (DSC), mechanical analyses and chemical resistance to concentrated acid and alkali solutions. Whatever the alkyl chains length and the DS, all samples displayed a layered structure composed of a planar arrangement of parallel cellulosic backbones with fully extended flexible side chains oriented perpendicular to the planar structure without interdigitation. The alkyl chains were able to crystallize as soon as they are long enough. As the DS decreased, the plasticizing effect of the alkyl chains was less pronounced and their ability to crystallize was improved. Regarding the mechanical behavior and the chemical resistance, similar results were observed whatever the DS is.

Impact of Cellulose Dissolution on 1-Butyl-3-Methylimidazolium Chloride Crystallization Studied by Raman Spectroscopy, Wide-Angle X-ray Scattering, and Solid-State NMR

Ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl) is a widely applied solvent for cellulose. In this work, we studied the crystallization behavior of bmimCl in the presence of cellulose, a...

Study on the formation mechanism of a flat rheology by poly(diethylenetriamine dimer acid amide) and organoclay in nonaqueous drilling fluids over a wide temperature range

This work aims to establish the relationship between the morphology and rheology changes affected by the addition of Flat-rheology modifier (FRM) to organoclay (OC)/white oil dispersions between 2 and 65 °C to analyze the flat-rheology formation mechanism in nonaqueous drilling fluids. The FRM used in this work is poly(diethylenetriamine dimer acid amide), and the OC is organo-montmorillonite. Temperature-controlled rheological tests confirmed that FRM addition to dispersions with low OC loadings (lower than 3.0 wt%) results in a relatively constant gel strength from 2 to 65 °C. This could be explained by the morphology variations in the dispersions generated by the FRM. Based on macroscopic settlement, particle size distribution, optical microscopy, transmission electron microscopy (TEM) and wide-angle X-ray scattering (WAXS) results, FRM molecules were inserted into and enlarged the interlayer space between OC platelets, thus reducing the particle size and improving the dispersion stability. Subsequently, the original card house network formed by OC particles was destroyed, and a new network with a larger volume fraction was formed by the highly dispersed platelets and FRM molecules. The increase in network volume fraction and extension of FRM molecular carbon chains with increasing temperature inhibit network strength deterioration. As a result, the rheological properties at 65 °C remained similar to those at 2 °C, thereby forming a flat rheology.

Laser nanostructuring of thin films of PEDOT:PSS on ITO: Morphology, molecular structure and electrical properties

Nanostructuring is one promising alternative to modify the functionalities of conducting polymers aiming at applications in technologies like organic solar cells, organic field-effect transistors and organic light-emitting diodes. Nowadays, there is an increasing interest in alternative ways of nanostructuring more economic, quicker and reproducible, avoiding the necessity of stringent environmental conditions like clean rooms, high vacuum or complex mask fabrication. Here we prove that Laser Induced Periodic Surface Structures (LIPSS) can be formed in films of Poly(3,4-ethylenedioxythiophene) complexed with Poly(styrenesulfonate) (PEDOT:PSS) prepared by spin-coating on planar Indium Tin Oxide. PEDOT:PSS has been irradiated with the 4th harmonic of a Nd:YAG laser resulting in LIPSS parallel to the laser polarization with a period close to the laser wavelength. LIPSS morphology has been characterized by Atomic Force Microscopy (AFM) and synchrotron Grazing Incidence Small Angle X-ray Scattering while the film structure was studied by Grazing-Incidence Wide-Angle X-ray Scattering and Raman spectroscopy. To analyze the impact of laser treatment on the electrical properties of PEDOT:PSS, conductive AFM was employed showing that LIPSS partially preserve the original electrical conductivity. These results can be of interest for achieving functional polymer nanostructures by a quick and reproducible approach with no need for clean room conditions.

Spectroscopic investigations on PVDF‐Fe2O3 nanocomposites

ABSTRACTPolyvinylidene fluoride‐iron oxide (PVDF‐Fe2O3) nanocomposites have been obtained my melt mixing of PVDF with Fe2O3 nanoparticles. The interactions between the polymeric matrix and the nanofiller have been investigated by wide angle X‐ray scattering (WAXS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, using both red and green excitations (lasers). WAXS, FTIR, and Raman spectra confirm that all samples contain α PVDF as the major crystalline form of the polymeric matrix. Experimental data revealed small changes in the positions of X‐ray lines as well as modifications of the width of X‐ray lines upon loading by Fe2O3 nanoparticles. FTIR and Raman spectra are dominated by the lines of the polymeric matrix. Within the experimental errors, the positions of Raman lines are not affected by the wavelength of the incoming electromagnetic radiation, although they are sensitive to the strain of the polymeric matrix induced by addition of the nanofiller. The loading of the polymeric matrix with nanoparticles stretches the macromolecular chains, affecting their vibrational spectra (FTIR and Raman). A complex dependence of the positions of some Raman and FTIR lines on the loading with Fe2O3 is reported. The manuscript provides a detailed analysis of the effects of nanofiller on the position of WAXS, FTIR, and Raman lines. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48907.

SAXS signature of the lamellar ordering of ionic domains of perfluorinated sulfonic-acid ionomers by electric and magnetic field-assisted casting.

At present, small angle X-ray scattering (SAXS) studies of perfluorinated sulfonic-acid ionomers (PFSAs) are unable to fully determine the true shape of their building blocks, as recent SAXS modelling predicts disk- and rod-like nanoionic domains as being equally possible. This scenario requires evidence-based findings to unravel the real shape of PFSA building blocks. Herein, a SAXS pattern signature for a lamellar nanophase separation of the ionic domains of Nafion is presented, backed by mid and far infrared spectroscopy (MIR and FIR) and wide angle X-ray scattering (WAXS) data of Nafion in different ionic forms, a broad range of ionic phase contents (EW ∼ 859-42 252 g eq-1) and temperatures. The study indicates that the lamellar arrangement of the ionic domains is the most representative morphology that accounts for the physical properties of this ionomer. The lamellar SAXS reflections of Nafion are enhanced in electric and magnetic field-aligned membranes, as confirmed by atomic force microscopy (AFM). Electric and magnetic field-assisted casting of Nafion allowed producing nanostructured and anisotropic films with the lamellas stacked perpendicularly to the field vector, which is the direction of interest for several applications. Such nanostructured Nafion membranes are bestowed with advanced optical and proton transport properties, making them promising materials for solar and fuel cells.

Thermo-oxidative stability and flammability properties of bamboo/kenaf/nanoclay/epoxy hybrid nanocomposites.

In this study, three types of nanoclay [halloysite nanotube (HNT), montmorillonite (MMT) and organically modified MMT (OMMT)] were incorporated into bamboo/kenaf (B/K) reinforced epoxy hybrid composites to compare their thermo-oxidative (TOD) stability and flammability properties. B/K (50 : 50) hybrid nanocomposites were fabricated by adding 1% loading (by weight) nanoclay through a hand lay-up technique. Wide angle X-ray scattering (WAXS) and field emission scanning electron microscopy (FESEM) were used to study the morphology of the nanoclay–epoxy mixture. The TOD stability of the hybrid nanocomposites was studied with a thermogravimetry analyzer (TGA) under oxygen atmosphere. The flammability properties were evaluated using the Underwriters Laboratories 94 horizontal burning test (UL-94HB), limiting oxygen index (LOI), cone calorimetry and smoke density test. The morphological study reveals that MMT/epoxy and HNT/epoxy are highly agglomerated while OMMT/epoxy reveals a more uniform distribution morphology. The obtained results reveal that B/K/HNT shows better TOD stability below 300 °C, but B/K/MMT and B/K/OMMT show high residue content and decomposition temperatures above 300 °C. The flame retardancy of the hybrid nanocomposites improved with the loading of all types of nanoclay, but B/K/OMMT shows higher flame retardancy than B/K/MMT and B/K/HNT hybrid nanocomposites. Hybrid nanocomposites show improvement in flame properties in terms of peak heat release rate (pHRR), total heat release, fire growth rate index (FIGRA) and maximum average rate of heat emission (MARHE) and smoke growth rate index (SMOGRA) indicators. The findings from this work can be utilized to prepare high-performance fire retardant natural fiber reinforced epoxy hybrid composites for automotive and construction applications to save human lives.

Anisotropic phase-separated morphology of polymer blends directed by electrically pre-oriented clay platelets.

We describe a general pathway to prepare an anisotropic phase-separated polystyrene (PS) - poly(vinyl methyl ether) (PVME) blend morphology by using electrically pre-orientated clay platelets. The clay platelets were oriented in a PS/PVME blend by means of an externally applied AC electric field while the blend is in one phase. Following orientation step, phase separation of the blends was induced by a temperature jump above their lower critical solution temperature (LCST) in the presence of the oriented clay platelets. In this process, an early stage co-continuous PS/PVME morphology coarsened and turned anisotropic phase-separated morphology parallel to the direction defined by clay planes oriented by AC electric field. The degree of anisotropy of PS/PVME phase-separated morphology was characterized by image analysis and that was found to be linearly proportional to the degree of orientation of clay platelets obtained by a 2D Wide Angle X-ray Scattering (WAXS). Transmission Electron Microscope (TEM) image of the blend morphology revealed that clay platelets oriented to AC field direction were located in a PVME phase. The electrically ordered column structures of clay platelets in the PVME phase yielded anisotropic PS diffusion during the phase separation. This process provides a unique new way to develop directionally organized phase-separated morphology from partially miscible binary blends using nanoparticles in combination with an external electric field.

Crystallization kinetics of rapid spray plasma processed multiple cation perovskites in open air

Wide angle X-ray scattering of perovskite conversion in ∼100 ms using rapid spray plasma process.

Microfibers synthesized by wet-spinning of chitin nanomaterials: mechanical, structural and cell proliferation properties.

Partially deacetylated chitin nanofibers (ChNF) were isolated from shell residues derived from crab biomass and used to prepare hydrogels, which were easily transformed into continuous microfibers by wet-spinning. We investigated the effect of ChNF solid content, extrusion rate and coagulant type, which included organic (acetone) and alkaline (NaOH and ammonia) solutions, on wet spinning. The properties of the microfibers and associated phenomena were assessed by tensile strength, quartz crystal microgravimetry, dynamic vapor sorption (DVS), thermogravimetric analysis and wide-angle X-ray scattering (WAXS). The as-spun microfibers (14 GPa stiffness) comprised hierarchical structures with fibrils aligned in the lateral direction. The microfibers exhibited a remarkable water sorption capacity (up to 22 g g−1), while being stable in the wet state (50% of dry strength), which warrants consideration as biobased absorbent systems. In addition, according to cell proliferation and viability of rat cardiac myoblast H9c2 and mouse bone osteoblast K7M2, the wet-spun ChNF microfibers showed excellent results and can be considered as fully safe for biomedical uses, such as in sutures, wound healing patches and cell culturing.

Grazing-Incidence Small-Angle X-Ray Scattering (GISAXS) and Grazing-Incidence Wide-Angle X-Ray Scattering (GIWAXS) Comparative Study on Malignant and Benign Human Cancer Cells and Tissues under Synchrotron Radiation

In the current study, we have experimentally and comparatively investigated and compared malignant human cancer cells and tissues before and after irradiating of synchrotron radiation using Grazing-Incidence Small-Angle X-Ray Scattering (GISAXS) and Grazing-Incidence Wide-Angle X-Ray Scattering (GIWAXS). It is clear that malignant human cancer cells and tissues have gradually transformed to benign human cancer cells and tissues under synchrotron radiation with the passing of time.

Structure architecture and morphology changes study in nylon 6/12 copolymers through anionic copolymerization via Response Surface Methodology modeling

The objective of this study was to investigate and characterize the morphology changes in nylon 6/12 with the variation of the initiation system in anionic copolymerization as well as optimization of initiation system via statistical Response Surface Methodology (RSM) modeling. At first, the random structure was directly proved through Carbon-13 (C13) nuclear magnetic resonance (13C NMR) analysis. However, in the course of study, considering both 13C NMR and Proton nuclear magnetic resonance (1H NMR) signals, comonomer placement alteration in chain structure was realized; the higher the loading of initiator, the more hand in hand embedding of ω-laurolactam (LL) comonomers in the polymer backbone. Wide-Angle X-ray Scattering (WAXS) was performed to identify crystal structural changes with alteration of the initiator and catalyst contents, and further supported the observations. Thermal analysis performed and, the above conclusions were confirmed with Differential Scanning Calorimetry (DSC) curves too.

Structure Development in Polymers during Fused Filament Fabrication (FFF): An in Situ Small- and Wide-Angle X-ray Scattering Study Using Synchrotron Radiation

Microstructure formation in individual layers during fused filament fabrication (FFF) of a Π-shaped multilayer single-walled polymer sample was studied by simultaneous measurement of small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) methods employing synchrotron radiation. We investigated individual layers and the welding zone between individual layers. As a model material, we used isotactic polypropylene (iPP), which is a commodity semicrystalline polymer and has a strong potential as a feedstock material for additive manufacturing. The layers were deposited by an FFF three-dimensional (3D) printer that was custom-built to fit into the synchrotron beamline. WAXS data were utilized to determine the temperature of the irradiated volume. The polymer microstructure was characterized in terms of crystallinity and long-spacing. Avrami analysis indicates that the crystallization behavior of iPP in thin layers is rather similar to that observed in quiescent crystallization of bulk iPP, suggest...

The Effect of Bi-Functionalized MMT on Morphology, Thermal Stability, Dynamic Mechanical, and Tensile Properties of Epoxy/Organoclay Nanocomposites.

In this work, the optimum filler loading to prepare epoxy/organoclay nanocomposites by the in-situ polymerization method was studied. Bi-functionalized montmorillonite at different filler loading (0.5, 1.0, 2.0, 4.0 wt %) was dispersed in epoxy resin by using a high shear speed homogenizer. The effect on morphology, thermal, dynamic mechanical, and tensile properties of the epoxy/organoclay nanocomposites were studied in this work. Wide-angle X-ray scattering (WAXS) and field emission scanning electron microscope (FESEM) studies revealed that possible intercalated structures were obtained in epoxy/organoclay nanocomposites. Thermogravimetric analysis (TGA) shows that epoxy/organoclay nanocomposites exhibit higher thermal stability at the maximum and final decomposition temperature, as well as higher char content, compared to pristine epoxy. The dynamic mechanical analysis (DMA) indicate that storage modulus (E′), loss modulus (E″), cross-link density and glass transition temperature (Tg) of the nanocomposites were improved with organoclay loading up to 1 wt %. Beyond this loading limit, the deterioration of properties was observed. A similar trend was also observed on tensile strength and modulus. We concluded from this study that organoclay loading up to 1 wt % is suitable for further study to fabricate hybrid nanocomposites for various applications.

Temperature dependent network properties of amorphous PCT during tensile stretching

Tensile deformation behavior of amorphous Poly (1,4-cyclohexylenedimethylene Terephthalate) (PCT) at 25 °C–108 °C was investigated by means of in situ synchrotron wide-angle X-ray scattering (WAXS). WAXS patterns were processed in a way that the scatterings from isotropic and anisotropic structures were separated. It turned out that the influences of temperature during deformation can be divided into three zones: below 80 °C, only molecular chains oriented; between 80 °C to 90 °C, very few imperfect crystals were induced by strain; above glass transition temperature (92 °C), the triclinic PCT crystalline structure began to form during deformation process. It was found that the Gaussian model of Haward and Thackray described the stress-strain behavior of the tensile stretched amorphous PCT very well. However, when being stretched above 80 °C, the system showed two characteristic network moduli because of strain-induced crystallization. The onset of change in network modulus occurred immediately after the formation of unoriented crystallites which served as physical cross-linking points to reinforce the material.

Multiscale synchrotron scattering studies of the temperature-dependent changes in the structure and deformation response of a thermoplastic polyurethane elastomer

The distinct molecular architecture and thermomechanical properties of polyurethane block copolymers make them suitable for applications ranging from textile fibers to temperature sensors. In the present study, differential scanning calorimetry (DSC) analysis and macroscopic stress relaxation measurements are used to identify the key internal processes occurring in the temperature ranges between −10 °C and 0 °C and between 60 °C and 70 °C. The underlying physical phenomena are elucidated by the small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) study of synchrotron beams, allowing the exploration of the structure-property relationships as a function of temperature. In situ multiscale deformation analysis under uniaxial cyclic thermomechanical loading reveals a significant anomaly in the strain evolution at the nanoscale (assessed via SAXS) in the range between −10 °C and 0 °C owing to the ‘melting’ of the soft matrix. Furthermore, WAXS measurement of crystal strain within the hard regions reveals significant compressive residual strains arising from unloading at ∼60 °C, which are associated with the dynamic shape memory effect in polyurethane at these temperatures.

Porous high amylose rice starch modified by amyloglucosidase and maltogenic α-amylase

Porous starch is attractive by providing high surface area for many applications. In this study amyloglucosidase (AMG) and maltogenic α-amylase (MA) were investigated in direct comparison to elucidate potential effects in producing porous starch using high amylose rice starch as a substrate. Both enzymes generated pores at the surface as illustrated by Scanning Electron Microscopy (SEM). The enzyme-treated granules had higher relative crystallinity as deduced from Wide Angle X-ray Scattering (WAXS). MA treatment increased the number of short amylopectin chains and decreased the molecular weight with extended incubation time. The MA-treated starch had higher solubility whereas swelling capacity, amylose content, peak viscosity, final viscosity, breakdown and setback of both treatments were decreased compared to the control. Enzymatic treatments produced starch with delayed gelatinization temperature and increased the enthalpy. The results demonstrate that porous rice starch can provide different functionalities depending on the enzyme mechanisms, extending the range of applications.

Experimental analysis and mechanical modeling of effect of stress-relaxation on shape memory and recovery behavior of e-beam irradiated HDPE

The thermo-sensitive shape memory behavior of electron beam crosslinked high-density polyethylene (EB-XL-HDPE) was analyzed in terms of effects of processing variables (dose, stretch ratio and programming temperature) on the recovery behavior of the EB-XL-HDPE. Shape memory induced above the melting temperature revealed an instant recovery with higher initial recovery temperature as compared to the samples programmed at crystallization temperature, well correlated with the observed differences in their crystallite size, crystal orientation and degree of crystallinity analyzed by wide-angle X-ray scattering (WAXS). The WAXS on orientation of crystalline domains in the stretched specimens confirmed breakdown of crystallites and formation of an uneven crystallite size as a result of stretching of specimens in the semi-crystalline state below melting temperature. With the increase in programming temperature, the relative orientation of stretched EB-XL-HDPE is increased due to greater flow of the plastic phase, thus enhancing the recoverability. A four-element mechanical model was developed to simulate and predict recoverability and stress relaxation behavior of the shape memory EB-XL-HDPE. By adjusting model parameters, the model described precisely the experimentally measured shape memory behavior of EB-XL-HDPE and predicted its recovery behavior. It is concluded that the stress relaxation phenomenon is accountable for partial recovery of the EB-XL-HDPE remained under sustained stress.