Wide-angle X-ray Scattering Measurements Research Articles

Isolating the interface of an emulsion using X-ray scattering and tensiometry to understand protein-modulated alkylglyceride crystallisation

HypothesisDairy proteins and mono- and diglycerides (MDG) are often used in unison to tailor the properties of dairy-based emulsions. However, there are significant gaps in our understanding of how proteins affect lipid crystallisation at the oil–water interface. We have used a unique combination of interfacially-sensitive techniques to elucidate the impact of dairy proteins on interfacial MDG crystal formation. ExperimentsThe formation temperature of interfacial MDG crystals was assessed through interfacial tension studies via drop shape analysis. Small and Wide-Angle X-ray Scattering measurements were performed on isolated oil–water interfaces, allowing for in-situ interrogation of MDG crystal structure and concentration at and near the interface. FindingsDairy proteins are seen to reduce the temperature at which MDG crystals form at the oil–water interface. The displacement of proteins upon interfacial crystal formation was also clearly observed in interfacial tension measurements. For the first time, lipid crystals formed at the oil–water interface have been characterised using X-ray scattering. All scattering studies showed no change to the MDG crystal structures at the oil–water interface in the presence of adsorbed proteins. The results demonstrate that informed selection of emulsifier components is critical to controlling interfacial crystallisation with concomitant impact on emulsion stability.

Macro- and Microstructural Evolution during Drying of Regenerated Cellulose Beads.

The macro- and microstructural evolution of water swollen and ethanol swollen regenerated cellulose gel beads have been determined during drying by optical microscopy combined with analytical balance measurements, small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS). Two characteristic length scales, which are related to the molecular dimension of cellulose monomer and elongated aggregates of these monomers, could be identified for both types of beads by SAXS. For ethanol swollen beads, only small changes to the structures were detected in both the SAXS and WAXS measurements during the entire drying process. However, the drying of cellulose from water follows a more complex process when compared to drying from ethanol. As water swollen beads dried, they went through a structural transition where elongated structures changed to spherical structures and their dimensions increased from 3.6 to 13.5 nm. After complete drying from water, the nanostructures were characterized as a combination of rodlike structures with an approximate size of cellulose monomers (0.5 nm), and spherical aggregates (13.5 nm) without any indication of heterogeneous meso- or microporosity. In addition, WAXS shows that cellulose II hydrate structure appears and transforms to cellulose II during water evaporation, however it is not possible to determine the degree of crystallinity of the beads from the present measurements. This work sheds lights on the structural changes that occur within regenerated cellulose materials during drying and can aid in the design and application of cellulosic materials as fibers, adhesives, and membranes.

Combinatorial Tuning of Structural and Optoelectronic Properties in CuxZn1−xS

Summary P-type transparent conductors (TCs) are important enabling materials for optoelectronics and photovoltaics, but their performance still lags behind n-type counterparts. Recently, semiconductor CuxZn1−xS has demonstrated potential as a p-type TC, but it remains unclear how properties vary with composition. Here, we investigate CuxZn1−xS across the entire alloy space (0 ≤ x ≤ 1) using combinatorial sputtering and high-throughput characterization. First, we find a metastable wurtzite alloy at an intermediate composition between cubic endpoint compounds, contrasting with solid solutions or cubic composites (ZnS:CuyS) from the literature. Second, structural transformations correlate with shifts in hole conductivity and absorption; specifically, conductivity increases at the wurtzite phase transformation (x ≈ 0.19). Third, conductivity and optical transparency are optimized within a "TC regime" of 0.10

9,9′-Bifluorenylidene-diketopyrrolopyrrole donors for non-polymeric solution processed solar cells

We have synthesised new materials comprised of 9,9′-bifluorenylidene and dithienodiketopyrrolopyrrole units. While 9,9′-bifluorenylidene has been primarily used in non-fullerene acceptors, when used in combination with the diketopyrrolopyrrole moiety it can form donor materials that can be used in conjunction with fullerene acceptors. The compounds differ in the substituents on the 9,9′-bifluorenylidene (protonated = 1A and dimethoxy = 1B) moiety. The structure of both the neat and blend films with PC70BM were found to be strongly dependent on the processing solvent used. In particular, Grazing Incidence Wide Angle X-ray Scattering measurements of films of 1A or 1B blended with PC70BM prepared from chloroform or chloroform with o-dichlorobenzene as an additive showed that the donor material had no particular ordering. However, when 1,8-diiodooctane was added to the processing solvent the 1A blends showed liquid crystalline ordering while 1B formed well-defined crystallites with three-dimensional ordering. The difference in film structure had a profound effect on the device properties. For 1A the optimised blend ratio with PC70BM was 1:4, but when 1,8-diiodooctane was used as the additive the best ratio of 1A to fullerene was 1:1. The films containing the well-defined crystallites of 1B all performed poorly, which was ascribed to a lack of a percolation pathway for hole extraction. The best performing device was comprised of a 1:1 blend of 1A and PC70BM, which had a power conversion efficiency of 2.6%.

The effects of transition metal sulfates on cellulose crystallinity during accelerated ageing of silver fir wood

During the hydrolytic degradation of cellulose caused by acidic transition metal sulphates, new low molecular products such as monosaccharides and their degradation products are usually formed which can increase the cellulose sensitivity to oxidation. This work was aimed at elucidation of the chemical and structural changes of cellulose in silver fir (Abies alba Mill.) wood treated with iron, copper and zinc salts to achieve a detailed understanding of cellulose deterioration during accelerated ageing. Cellulose samples were isolated from the wood by the Kurschner-Hoffer method and the Seifert method. Changes in cellulose structure were evaluated by wide-angle X-ray scattering (WAXS) measurements, Fourier transform infrared spectroscopy (FTIR), and high performance liquid chromatography. The presence of metal cations (Cu2+, Zn2+, Fe3+) caused a significant loss in the content of cellulose for treated and aged wood samples. Wet-thermal accelerated ageing led to a decrease (~ 20%) in the content of monosaccharides. The Seifert cellulose samples had a higher crystallinity than the Kurschner-Hoffer samples. A strong correlation was found between crystallinity indices obtained from the FTIR and WAXS measurements. Two cluster groups of cellulose samples, segregated from each other, were identified within each cellulose type in a multivariate cellulose trait analysis.

The influence of a magnetic field on the morphology and thermomechanical properties of a liquid crystalline epoxy carbon composite

The synthesis of a novel ordered liquid crystalline epoxy carbon composite was presented in this article. Anthracite thermally modified at 2,000°C (SV2000) having graphitic structure was used as a filler in the composite with matrix obtained by crosslinking a liquid crystalline diepoxy monomer LCEM containing triaromatic mesogenic group. The curing agent was 4,4′‐diaminodiphenylmethane. The morphology and thermomechanical properties of the final products were characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and wide angle X‐ray scattering (WAXS) analysis. It was found by WAXS measurements that alignment of LCEM was effectively induced in the matrix and in the composite filled with SV2000 by applying external magnetic field during cure. Thermosets with locked smectic C structure were obtained in all cases, with mesogenic fragments arranged along the applied field. The experimental results indicated that the presence of SV2000 as the filler of composite partially decreased the degree of order. The oriented composites exhibited anisotropy of the dynamic‐mechanical properties. POLYM. COMPOS., 39:E2573–E2583, 2018. © 2018 Society of Plastics Engineers

Time-Resolving Study of Stress-Induced Transformations of Isotactic Polypropylene through Wide Angle X-ray Scattering Measurements.

The development of a highly oriented fiber morphology by effect of tensile deformation of stereodefective isotactic polypropylene (iPP) samples, starting from the unoriented γ form, is studied by following the transformation in real time during stretching through wide angle X-ray scattering (WAXS) measurements. In the stretching process, after yielding, the initial γ form transforms into the mesomorphic form of iPP through mechanical melting and re-crystallization. The analysis of the scattering invariant measured in the WAXS region highlights that the size of the mesomorphic domains included in the well oriented fiber morphology obtained at high deformations increases through a process which involves the coalescence of the small fragments formed by effect of tensile stress during lamellar destruction with the domain of higher dimensions.

Direct investigations on strain-induced cold crystallization behavior and structure evolutions in amorphous poly(lactic acid) with SAXS and WAXS measurements

Strain-induced cold crystallization behavior and structure evolution of amorphous poly(lactic acid) (PLA) stretched within 70–90 °C were investigated via in situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements as well as differential scanning calorimetry (DSC) measurements. The data obtained from the stretched samples within 70–90 °C showed that all of the formed crystals are disordered α′ form with more compact chain packing than that of the cold crystallization. Upon stretching at 70 °C, the mesocrystal appears first then forms crystal with strain increasing. The stacked structure consisting of less perfect crystalline phase, mesocrystal and oriented amorphous phase emerges at the final stage of stretching. Drawing at 80 °C, only the crystal can be induced at lower strain with higher crystallization rate. With strain increasing, the crystallinity and crystal orientation increase, leading to the formation of analogous ‘shish-kebab’. The structure evolution at 90 °C is similar to that at 80 °C, but with much earlier crystallization onset and higher crystallization rate. The difference in strain-induced crystallization behavior of amorphous PLA within 70–90 °C can be attributed to the competition between chain orientation caused by stretching and chain relaxation. It was proposed that the strain-induced mesocrystal/crystal and the lamellae are formed from the mesophase originally existing in PLA glass according to the obtained data.

Study on the stretch induced phase transition of α trans-1,4-polyisoprene by in-situ SAXS and WAXS measurements

Trans-1,4-polyisoprene (trans-PI) is an important industrial polymer, which exhibits pronounced polymorphisms. However, understanding of the crystal form transition of trans-PI is rather limited. In the present work, the stretch-induced crystal form transition of α trans-PI at room temperature was investigated in detail. It was found that the β crystals with high molecular chain orientation appeared at strain = 0.,42 and the total crystallinity increased at the same time. Meanwhile, the average long spacing (l ac), thickness of lamellae (l c), and amorphous layers (l a) along the stretching direction had undergone multiple evolution processes during stretching. Results also showed that part of the amorphous phase and the recrystallization process of α crystals both contributed to the formation of the β form. Based on the combination analysis of the in-situ SAXS (small angle X-ray scattering), WAXS (wide angle X-ray scattering), differential scanning electron microscopy (DSC), and Fourier transform infrared spectroscopy (FTIR), it was proved that the β mesophase with layered structure emerged before the formation of β crystals. Finally, a possible multistage evolution mechanism was proposed to interpret the stretch-induced crystal form transition of α trans-PI.

Changes of crystalline structure of poly(ethylene terephthalate) fibers in flame retardant finishing process

The poly(ethylene terephthalate) (PET) fibers of improved flammability were investigated. The modification applied to classic PET fibers consisted in a wet flame-retardant treatment of the fabrics during the dyeing process. In this study we took an attempt to describe the supermolecular structure of the flame retardant PET fibers with different content of the modifier as a function of a temperature of the flame retardant finishing process and additionally the structure transformation during the ageing process. To evaluate the crystalline structure of fibers differential scanning calorimetry (DSC) and wide angle X-ray scattering measurements (WAXS) were used.

Mutual conversion between stretched and contracted helices accompanied by a drastic change in color and spatial structure of poly(phenylacetylene) prepared with a [Rh(nbd)Cl]2-amine catalyst

The yellow-colored poly(phenylacetylene), Poly(Y), is obtained from phenylacetylene using a [Rh(nbd)Cl]2-NEt3 catalyst in ethanol at 25 °C. The color of Poly(Y) drastically changes into red Poly(R) or reddish-black Poly(B) by immersion in acetylacetone or exposure to chloroform vapor, respectively. Poly(R) is also created from Poly(B) by contact with acetylacetone. Poly(Y) is regenerated from both Poly(R) and Poly(B) by reprecipitation from their chloroform solution into methanol. Wide-angle X-ray scattering (WAXS) patterns of Poly(Y) and Poly(R) correspond to a pseudohexagonal crystal called a columnar as stretched cis-transoid and contracted cis-cisoid helices, respectively. These helical diameters and pitch widths obtained from the WAXS measurements are agreed with those of MMFF94 calculation models. The smallest helical pitch width is 3.3 Å for Poly(R) and Poly(B). Moreover, information regarding the size and ordering of the vacant space within each polymer is estimated by using 129Xe NMR technique. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 752–759

Poly(ester urethane) with Varying Polyester Chain Length: Polymorphism and Shape‐Memory Behavior

The swelling, viscoelastic, and mechanical behavior of phase‐segregated poly(ester urethane) (PEU) block copolymers, composed of 4,4′‐methylenediphenyl diisocyanate, 1,4‐butanediol as a chain extender, and crystallizable poly(1,4‐butylene adipate) (PBA) with molecular weights between 1330 and 4120 g mol−1, are investigated. Wide‐angle X‐ray scattering (WAXS) is employed to study the overall PEU crystallinity, which increases from 8.6 to 13.6% at higher PBA contents. The existence of two crystalline, polymorphic PBA phases, a thermodynamically stable α phase and a metastable β phase, is confirmed by further WAXS measurements. Calorimetric and thermomechanical investigations give evidence for controllable PBA polymorphic behavior. The crystallization conditions, like the cooling rate, affect the emerging polymorphic mixture, whereas the storage conditions either promote or inhibit the polymorphic (β to α) transition. The introduced concepts represent a new approach for gaining control over programmable thermo­responsiveness, which may be transferable to other shape‐memory polymers with polymorphic switching segments. image

Study of the crystalline phase orientation in uniaxially stretched polypropylene by Raman spectroscopy: Validation and use of a time‐resolved measurement method

AbstractThis study proposes an experimental method to quantify the molecular orientation of the crystalline phase of isotactic polypropylene from polarized Raman spectroscopy measurements. The method is based on the intensity sensitivity of two Raman scattering bands located at 973 (C‐C stretching mode) and 998 cm−1 (CH3 rocking mode) to laser light polarization. The first part of this article is devoted to the validation of the method by comparing Raman and Wide Angle X‐ray Scattering (WAXS) results obtained on postmortem test samples uniaxially deformed at growing levels. Second, the method is applied to follow the molecular orientation in situ during a tensile test by combining a video‐controlled test machine and a Raman spectrometer. Postmortem results show a quantitative agreement between Raman and WAXS measurements. In situ results mainly evidence the ability of the Raman method to characterize molecular orientation in real‐time with less than 5 s time resolution. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers .

Elucidation of the Orientational Order and the Phase Diagram of p-Quinquephenyl

The orientational order in the nematic phase of p-quinquephenyl, the pentamer of p-phenylene, has been determined by means of birefringence measurements and by wide-angle X-ray scattering (WAXS). The experimentally determined order parameters <P(2)> are compared with the temperature-dependent order parameter predicted by the Maier-Saupe theory. The order parameters derived from the birefringence at different temperatures in the nematic phase of p-quinquephenyl were in excellent agreement with the Maier-Saupe predictions. The <P(2)> values calculated from the azimuthal profiles derived from WAXS measurements were significantly lower than those determined by the birefringence measurements, especially at higher temperatures. For the birefringence measurements, alignment of the director is achieved by using polyimide alignment layers, whereas director alignment for the WAXS experiments was achieved by a magnetic field. We assign the low overall order parameters that were measured by WAXS to a lower macroscopic orientational order. In addition, upon reinvestigating the mesophase behavior of p-quinquephenyl, a monotropic smectic A phase has been observed upon cooling at 390 °C, just before the crystallization temperature is reached.

Liquid crystalline epoxy thermoset with azomethine mesogen

This work is a continuation of our earlier investigations on the liquid crystalline epoxy resins containing azomethine as mesogen group. The present study concerns the curing reaction of an azomethine epoxy monomer, namely, N,N'-(1,4-phenylenedimethylidyne)-di-4-(2,3-epoxypropoxy) aniline (AZ-2) in the presence of 2-amino-biphenyl (2-ABPh), used as a curing agent. The crosslinking reaction, the phase transitions and the thermal properties of the synthesized thermoset were monitored by differential scanning calorimetry (DSC), polarized optical microscopy and wide-angle X-ray scattering (WAXS). The main thermal transitions observed by DSC in dynamic conditions are due to both melting of the mixture components and the crosslinking reaction. The reaction of AZ-2 monomer with 2-ABPh takes place in the temperature range from 184 to 278°C, and the process is accompanied with homopolymerization of the epoxy groups. The microscopic technique revealed the appearance of a smectic type mesophase, the result being confirmed by WAXS measurements.

Study of temperature dependence of crystallisation transitions of a symmetric PEO-PCL diblock copolymer using simultaneous SAXS and WAXS measurements with synchrotron radiation

The reversible transitions of the lamellae of a crystalline-crystalline diblock copolymer from the melt to crystallites were studied using simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements with synchrotron radiation. A symmetric poly(ethylene oxide)-poly( varepsilon -caprolactone) diblock copolymer was chosen for this study. We showed in the course of the block copolymer crystallisation that the time-resolved integrated intensity I (int) was proportional to the product of the volume fractions of the PEO and PCL phases and the scattering contrast due to the electron density difference. These results demonstrated that simultaneous SAXS/WAXS measurements could be used to monitor the crystallisation process in two domains of different sizes at the same time.

Structural evolution of the amorphous phase during crystallization of poly( l-lactic acid): A synchrotron wide-angle X-ray scattering study

Initially amorphous poly( l-lactic acid), PLLA, was crystallized at 80 °C, during which time-resolved wide-angle X-ray scattering measurements (WAXS) were performed using synchrotron radiation. The amorphous halo of the initial material (AM) and fully transformed semi-crystalline PLLA (SC) could be approximated by single Gaussian functions, and exhibited different features: for SC-PLLA the amorphous halo is found to be broad and shifted to higher 2 θ values, i.e. featuring a more compact/oriented arrangement than in AM-PLLA. Such results are consistent with previous dielectric and DSC results on PLLA that showed that the glass transition dynamic of SC-PLLA is characterized by a higher T g and by a broader distribution of characteristic times. For intermediate values of crystallization times, it was found that the amorphous halos of the WAXS profiles could be described by simple linear combinations of contributions of the AM and SC amorphous halos, in which the first one progressively vanishes, while a concomitant increase of the later is detected. Such results are in agreement with the description of the dielectric behavior found in PLLA during crystallization and provide an example where structural information could be linked with the segmental dynamic characteristics in semi-crystalline systems.

Higher-order Structure Analysis of Polyethylene Thin Films by In-situ Synchrotron Grazing-incdence Small-angle and Wide-angle X-ray Scattering Measurements

The higher-order structures of high-density polyethylene (HDPE) thin films on Si wafers have been investigated on lamellar and molecular levels by synchrotron grazing-incidence small-angle and wide-angle X-ray scattering (GISWAXS: GISAXS and GIWAXS) measurements, respectively. Annealing effect on molecular orientation and lamellar stacking structure of the thin films was clarified by in-situ GISWAXS measurements at BL40B2 in SPring-8 for the thin films in a stepwise annealing process from 378 K to 393 K under vacuum. The thin films with a thickness of ea. 400 nm were prepared by a dip-coating method. The two-dimensional GISAXS patterns of the thin films suggested that crystalline lamellae were alternately stacked with amorphous in the parallel direction to the substrate surface and the long period increased from ea. 26 nm to ea. 36 nm during annealing. Their two-dimensional GIWAXS patterns measured at the same time indicated that HDPE chains formed the orthorhombic crystal and the chain axis in a crystalline lamella oriented relatively parallel to the film surface.

Inorganic glasses, glass-forming liquids and amorphizing solids

We take familiar inorganic oxide glasses and non-oxide glasses and the liquids from which they derive to review the current understanding of their atomic structure, ranging from the local environments of individual atoms to the long-range order which can cover many interatomic distances. The structural characteristics of important glasses and melts, like silicates, borates, alumino-silicates, halides and chalcogenides, are drawn from the results of recent spectroscopy and scattering experiments. The techniques include Nuclear Magnetic Resonance (NMR) and X-ray Absorption Fine Structure (XAFS), Neutron Scattering (NS) and Small- and Wide-angle X-ray Scattering measurements (SAXS/WAXS), and are often combined with computer simulation experiments in order to obtain detailed images of structure and diffusion in the glassy as well as in the molten state. We then review the current understanding of relaxation in glasses, liquids and polyamorphic states. This includes phenomenological models and theories of rela...

Crystallization of Isotactic Polypropylene under Shear Flow Observed in a Wide Spatial Scale

We studied crystallization process of isotactic polypropylene (iPP) under shear flow as a function of shear rate using time-resolved wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), depolarized light scattering (DPLS), and polarized optical microscopy (POM) to elucidate the formation mechanism of the so-called shish-kebab structure in a wide spatial scale from 0.1 nm to several tens of μm. In the time-resolved DPLS, SAXS, and WAXS measurements we observed the formation processes of the shish-like structure, the kebab structure, and the crystalline lattice (mostly in the kebab), respectively, and found that there were critical shear rates for the anisotropic structure formation in the DPLS, SAXS, and WAXS measurements. The values are very close each other, suggesting the anisotropic structure formations in both of the shish and the kebab are dominated by a common origin. Furthermore, comparing the onset times of intensities in DPLS, SAXS, and WAXS, we found that the onset of DPLS intensity is the most accelerated by the shear among the three. On the basis of the observations, we propose a possible mechanism for the shish-kebab structure.