Simultaneous Small-angle X-ray Scattering Research Articles

Isothermal crystallization of poly(glycolic acid) studied by terahertz and infrared spectroscopy and SAXS/WAXD simultaneous measurements

Isothermal crystallization of poly(glycolic acid) (PGA) has been studied using terahertz (THz) and infrared (IR) spectroscopy and simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements. Changes in the intermolecular interactions in PGA during the isothermal crystallization were monitored using THz spectroscopy, which is an efficient technique for analyzing the higher-order structure of polymers. In the THz spectra, the temporal difference in the intensity observed in the isothermal crystallization is due to the difference in the vibrational origins of two bands at 192 and 65 cm−1. The band at 192 cm−1 primarily originates from the intramolecular vibrational mode (twisting of the local structure of the PGA molecular chain). Furthermore, the band at 65 cm−1 exists due to the intermolecular vibration mode (C = O···H-C hydrogen bonds between polymer chains). In addition, these THz bands appeared after the appearance of the SAXS and WAXD peaks. When a lamellar structure is formed and the molecular chains are oriented, the THz band originating from the intermolecular vibration is observed. It is highly possible that the intermolecular vibration appearing in the THz spectra requires the molecular chains to be oriented. Isothermal crystallization of poly(glycolic acid) (PGA) was carried out using terahertz (THz) and infrared (IR) spectroscopy and simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements. The intensity of the absorption peak at 192 cm−1 increased before the increase in intensity of the peak at 65 cm−1 during the isothermal melt-crystallization process at 185 °C. This is due to a difference in the vibrational origins of these two bands. In addition, these THz bands appeared after the appearance of the SAXS and WAXD peaks

Education program for controversial defect of recent X-ray instrument termed as a simultaneous small angle X-ray scattering and wide angle X-ray diffraction measuring instrument

Abstract Simultaneous rotations of sample and X-ray detected counter are needed to evaluate orientation distribution of crystallites and amorphous chains oriented predominantly parallel to the film surface in addition to exact diffraction peak profiles obtained without the complicated intensity corrections. The rotation mode is known as “θ–2θ scanning” system (θ: film, 2θ: counter). The system has been mainly used in research and development institutes. However, such instruments are not produced at present. Recently, small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD) intensities have been measured by using X-ray beam generated along one direction. The brand name of the instrument is “a simultaneous SAXS and WAXD measuring instrument”. The X-ray beam generated by the instrument has surely high luminance providing high degree resolution of peak profiles by diffraction and/or scattering. The sample stage and detector, however, are fixed, since the intensities for SAXS and WAXD are obtained by the digital display of the number of X-ray photons detected on the imaging plate. Such optical system contains controversial defect on evaluating orientation of crystal planes parallel to the surface of films prepared by T-die and inflation methods as well as the exact profile. The imaging plate cannot detect the diffraction intensity from the crystal planes existing in the angle range between incident beam and Bragg angle associated with the diffraction peak position of the individual crystal planes.

Low-temperature and high-pressure phases of a room-temperature ionic liquid and polyiodides: 1-methyl-3-propylimidazolium iodide.

Using simultaneous small-angle X-ray scattering (SAXS) combined with differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) combined with DSC measurements, low-temperature (LT) solid phases of a room-temperature ionic liquid (RTIL) and its mixtures were examined at ambient pressure. The considered RTIL was 1-methyl-3-propylimidazolium iodide ([C3mim][I]), and the mixtures could be expressed as [C3mim][Im]. Under high-pressure (HP), the crystallization of pure [C3mim][I] was suppressed, as a LT-amorphous form of pure [C3mim][I] was formed. In the mixed system, the HP crystallization of [C3mim][I3] occurred at 0.95 GPa of compression. In [C3mim][I3.66] as a non-stoichiometric system, complicated phase changes were observed. Upon compression, the edge of a sample container was crystallized. By further compression, a crystal-crystal phase transition was observed as a HP-crystal polymorph appeared. In the centre, HP amorphization was observed upon compression, whereas decompression crystallization was induced by decreasing the pressure. The HP complicated behaviors of non-stoichiometric [C3mim][I3.66] are caused by the excess of iodide/iodine.

Simultaneous Small-Angle and Wide-Angle X-ray Scattering Analysis of Single Fibers for Criminal Investigation

Simultaneous Small-Angle and Wide-Angle X-ray Scattering Analysis of Single Fibers for Criminal Investigation

Strain-induced molecular aggregation states around a crack tip in a segmented polyurethane film under uniaxial stretching

The development of molecular aggregation structures during stretching deformation and local structure mapping around a crack tip of a segmented polyurethane elastomer film were investigated by in situ simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) and by micro-beam WAXD, respectively. Both the hard segment (HS) domain orientation and the strain-induced crystallization of poly(ε-caprolactone) chains were tracked by the WAXD pattern due to the high crystallinity of the symmetric non-bulky aliphatic HS structure. Strain-induced crystallization occurred locally at the vicinity of the crack tip, and the crystallinity immediately decayed in the exterior, whereas the HS domain orientation was observed throughout the stretched film. The mechanisms underlying crack arrest and the mechanical strength of polyurethane elastomer films are associated with the local strain-induced crystallization at the crack tip, the mechanical stability of the HS domains, and the avoidance of local stress concentration through the HS domain orientation.

Combining SAXS and DLS for simultaneous measurements and time-resolved monitoring of nanoparticle synthesis

Time-resolved characterization of nano-particle (NP) synthesis is a promising mean to produce NPs under controlled conditions. Here, an innovative experimental demonstration of a NP characterization tool which combines a laboratory Small Angle X-ray Scattering (SAXS) instrument, a new Dynamic Light Scattering (DLS) device and a microflow reactor is shown. The complementary SAXS and DLS techniques were designed and optimized to meet the ambitious requirements of time-resolved monitoring of NP suspensions while ongoing synthesis. For this purpose, SAXS instrument performance was enhanced by the implementation and optimization of a unique X-ray metal jet source. In parallel, an innovative DLS fiber remote probe head was developed specifically for in situ measurements. DLS measurements were performed directly inside a 2.0mm diameter glass capillary located inside the SAXS vacuum sample chamber. The combined SAXS and DLS devices were tested separately on commercially available gold NP suspensions of known size. Furthermore, simultaneous SAXS and DLS measurements were performed during the synthesis of silica NPs.

Cavitation in Block Copolymer Modified Epoxy Revealed by In Situ Small-Angle X-Ray Scattering.

Simultaneous small-angle X-ray scattering (SAXS) and tensile experiments were performed on epoxies modified with approximately 30 nm diameter rubbery and glassy core block copolymer micelles. The in situ SAXS data, interpreted using established analytical models, reveals efficient and coherent cavitation of the spherical rubbery cores coincident with yielding and absence of cavitation in the glassy nanodomains. These results are quantitatively anticipated by recent theory that accounts for cavitation in rubber toughened plastics as a function of particle size.

Clay orientation effect on the thermal stability of polyethylene–nanoclay nanocomposites

This paper explores the effect of nanoclay orientation on the long term thermal stability of a polyethylene (PE)/nanoclay nanocomposite. Nanoclay morphology and orientation in an injection molded PE–clay nanocomposite bar were examined using transmission electron microscopy and simultaneous small angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD). These nanocomposites were aged at elevated temperatures for various periods of time, and the relative amount of antioxidant (AO) was monitored using an oxidative induction time test. The presence of 4 wt% nanoclay accelerates AO depletion, particularly at the surface region of the sample. AO concentration profiles along different directions of the sample bar were constructed based on SAXS/WAXD results, and were correlated with the clay orientation. A detailed AO depletion mechanism is discussed.

Solution-Electrospun Poly(ethylene terephthalate) Fibers: Processing and Characterization

Electrospun poly(ethylene terephthalate) (PET) fibers were prepared from a trifluoroacetic acid (TFA)-based solvent. Rheological studies revealed the concentration (ϕ) dependence of the specific viscosity (ηsp) to be ηsp ∼ ϕ3.7 for PET/TFA solutions in the entangled regime. The determined entanglement concentration (ϕe) was higher using a lower-molecular-weight PET. To obtain bead-free fibers, the minimum concentration for the electrospinning was 0.8–1.0ϕe owing to the high volatility of TFA solvent, which significantly enhanced the chain network strength during jet whipping. The double-logarithmic plots of the jet (dj) and fiber (df) diameters versus the zero-shear viscosity (η0) revealed that two scaling laws existed for the present solutions, i.e., dj ∼ η00.06 and df ∼ η00.77. The microstructural evolution of the electrospun PET fibers from stepwise annealing to crystal melting was investigated by simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements using synchrotron radiation sources. The conformer transformation from gauche to trans was monitored by in-situ Fourier transform infrared spectral measurement. In the absence of any WAXD reflection, the as-spun PET fibers possessed a SAXS scattering peak, indicating the presence of a mesomorphic phase with an interdomain distance of 6.8 nm. At annealing temperatures (Ta) higher than 100 °C, the mesomorphic phase gradually transformed into imperfect triclinic crystals and reached its saturation at 130 °C. Further increased Ta perfected the triclinic structure without altering fiber crystallinity until the initial crystal melting at 218 °C, at which a significantly increased long period was detected. When the electrospun PET fibers were embedded in an isotactic polypropylene (iPP) matrix, surface-induced crystallization occurred to develop a transcrsytalline layer of iPP monoclinic crystals at the interface.

Block Copolymer Nanocomposites Based on Multiwall Carbon Nanotubes: Effect of the Functionalization of Multiwall Carbon Nanotubes on the Morphology of the Block Copolymer

AbstractFilms based on a commercial block copolymer and multiwall carbon nanotubes (MWCNTs) were prepared by solution casting. The block copolymer has a star asymmetric chain architecture, with polystyrene chains of different lengths and a polybutadiene core. The block copolymer has a lamellar morphology. The MWCNT were grafted with polystyrene chains under atom transfer radical polymerization (ATRP) conditions. The nanocomposites were characterized by transmission electron microscopy (TEM) and simultaneous small angle X‐ray scattering (SAXS)/strain–stress tests. The morphology of the nanocomposites is influenced by the polystyrene chain grafted from the MWCNT. In the case of the nanocomposite based on pristine MWCNT, most of the nanotubes intersect the lamellar domains of the block copolymer. With the increase of the molecular weight and the grafting chain density of the polystyrene anchored to the MWCNT, a favorable interaction between the polystyrene microdomain phases in the block copolymer and the MWCNT is observed. In the case where the MWCNT grafted with the relative highest molecular weight (20 kg·mol−1) and polystyrene grafted content (> 90 wt%), the MWCNT locally templates the lamellar morphology of the block copolymer. The effect on the block copolymer is analyzed based on the orientation of the morphology under an external deformation.

A real time SAXS study of oriented block copolymers during fast cyclical deformation, with potential application for prosthetic heart valves

Simultaneous small angle X-ray scattering (SAXS) and force measurements have been recorded during tensile loading/unloading deformation cycles of three oriented thermoplastic elastomers. SAXS patterns were obtained in only 10 ms, during deformation. Over this timescale, the microstructure of the materials reacted instantly to the applied deformation. Microstructural changes were followed over 10 000 cycles, each cycle period being less than 1 s. Morphological evolution from the initial state as the deformation proceeded has been linked to mechanical properties. The direction of orientation was the most significant parameter determining the mechanical strength of tested materials, followed by styrene weight fraction. Samples oriented parallel to the deformation direction showed greater resistance to applied force and also better microstructural reversibility over the 10 000 cycles.

A scanning SAXS/WAXS study of rat brain

A simultaneous SAXS (small-angle X-ray scattering) and WAXS (wide-angle X-ray scattering) measurement setup was installed at BL45XU in SPring-8. The system comprises of a short (specimen-to-sample distance about 50cm) vacuum path and a mosaic CCD detector. It covers a q-range of 0.02-2.5 nm−1. Using this setup, lipids in formalin-fixed rat brain were analyzed. A brain slice was moved across the X-ray beam with a step size of 0.5 mm to map reflections from lipids in various areas of brain. White matter that contains myelin gave strong lamellar reflections in the small-angle region which are often unisotropic. Gray matter shows only a central scatter in the small-angle region. In the wide angle region, both white and gray matters gave rise to sharp rings that are due to lateral packing of hydrocarbon chains in the lipid membranes. The relative intensities of these rings were different in white and gray matters, showing that the lateral arrangements of the lipids in bilayers are different.

Determining Nanoparticle Size in Real Time by Small-Angle X-ray Scattering in a Microscale Flow System

Precise in situ measurements are becoming more important as we seek to identify and harness the unique properties of novel nanomaterials, yet key challenges remain in determining structures with current analytical approaches. We report here an in situ multitechnique approach that permits the real-time measurement of the sizes of nanoparticles in flowing solutions. A series of ligand-stabilized Au nanoparticle standards (dCORE = 0.8−5 nm) was analyzed by simultaneous small-angle X-ray scattering (SAXS) and UV−vis spectroscopy in a microscale flow system. A specially designed observation cell provided access to both measurements at an identical location in the flow system and allowed for the correlation of SAXS and TEM analyses. Comparison of flow-based UV−vis data to those obtained ex situ provided a bridge between in situ SAXS and ex situ TEM measurements. Average core size from both techniques matched closely for each sample, while polydispersity values from SAXS measurements were smaller than those from TEM. By correlating in situ and ex situ measurements for well-defined nanoparticle standards, these experiments form the basis of a powerful approach to assess nanoparticle core size within flowing microscale systems.

Isothermal Crystallization Behavior of Isotactic Polypropylene H/D Blends as Viewed from Time-Resolved FTIR and Synchrotron SAXS/WAXD Measurements

The melt isothermal crystallization behavior has been investigated for a series of blend samples of deuterated (D) and hydrogenated (H) species of isotactic polypropylene by means of time-resolved Fourier transform infrared (FTIR) spectral measurement and simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements using synchrotron radiation source in SPring-8. The SAXS data collected were analyzed in the three different time regions. The Guinier plot in the early stage of crystallization gave the average size of isolated domains formed in the melt. In the middle stage, the correlation between these domains was analyzed using the Debye−Bueche equation. In the later stage of crystallization, the correlation function was calculated to estimate the degree of crystallinity and the long period of the stacked lamellae. The IR data analysis clarified the formation process of regular helical chains in the isothermal crystallization phenomenon. The combination of FTIR, WAXD, a...

Electrorheological properties of organically modified nanolayered laponite: influence of intercalation, adsorption and wettability

Cetyltrimethylammonium bromide (CTAB) modified synthetic laponite is synthesized by an ion exchange method and characterized by simultaneous small-angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), atomic force microscopy (AFM), thermal analysis and rheometry. Through the formation of the organoclay, the properties of clay change from hydrophilic to hydrophobic. Morphology results show that the hydrophilic particles are aggregating easily, whereas the suitable CTAB modified laponite can get near monodispersed nanoparticles due to its hydrophobic properties. It is proposed that CTAB is intercalated and adsorbed onto the laponite partially depending on the substituted concentration of the surfactant cation exchange capacity (CEC) (0.5CEC to 6CEC). The electrorheological (ER) effect is investigated for suspensions of CTAB modified laponite dispersed in silicone oil. The two-dimensional SAXS images from ER bundles of CTAB modified laponite exhibit markedly anisotropic SAXS patterns, giving a measure for laponite particle alignment within the ER structure. An optimum electrorheological effect can be attained at a particular CEC substituted concentration. On the basis of the structure analysis and dielectric measurements, we attribute the enhancement of ER activity to the improvement in the dielectric properties that showed an increase in the dielectric constant and the dielectric loss at low frequency and their regular optimum change with CTAB modification.

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.

Influence of cooling rate on the thermal behavior and solid‐state morphologies of polyhydroxyalkanoates

AbstractThe influence of cooling rates on the thermal behavior and solid‐state morphologies of polyhydroxyalkanoates have been investigated. The thermal behavior was studied by differential scanning calorimetry (DSC). The crystal structures (∼ Å), lamellar (tens of nanometers), fibrillar (several hundred nanometers), and spherulitic (∼ μm) morphologies of poly (3‐hydroxybutyrate) (PHB) and the copolymers of poly (3‐hydroxybutyric acid‐co‐3‐hydroxyvaleric acid) (PHBV) and poly (3‐hydroxybutyric acid‐co‐3‐hydroxyhexanoic acid) (PHBHx) crystallized under different cooling rates were studied using simultaneous small angle X‐ray scattering (SAXS) and wide angle X‐ray scattering, simultaneous ultra small angle X‐ray scattering (USAXS) and SAXS, and polarized optical microscopy, respectively. The experimental results showed that the lamellar and spherulitic morphologies depended strongly on cooling rates. However, there was little influence of cooling rates on the crystal structures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Acceleration or retardation to crystallization if liquid–liquid phase separation occurs: Studies on a polyolefin blend by SAXS/WAXD, DSC and TEM

Blends of statistical copolymers containing ethylene/hexene (PEH) and ethylene/butene (PEB) exhibited the behavior of upper critical solution temperature (UCST). The interplay between the early and intermediate stage liquid–liquid phase separation (LLPS) and crystallization of the PEH/PEB 50/50 blend was studied by time-resolved simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. Samples were treated by two different quench procedures: in single quench, the sample was directly quenched from 160°C to isothermal crystallization temperature of 114°C; while in double quench, the sample was firstly quenched to 130°C for 20min annealing, where LLPS occurred, and then to 114°C. It was found that in the early stage of crystallization, the integrated values of Iq2 and crystallinity, Xc, in the double quench procedure were consistently higher than those in the single quench procedure, which could be attributed to accelerated nucleation induced by enhanced concentration fluctuations and interfacial tension. In the late stage of crystallization, some morphological parameters were found to crossover and then reverse, which could be explained by retardation of lamellar growth due to phase separation formed during the double quench procedure. This phenomenon was also confirmed by DSC measurements in blends of different compositions at varying isothermal crystallization temperatures. The crystal lamellar thickness determined by SAXS showed a good agreement with TEM observation. Results indicated that the early stage LLPS in the PEH/PEB blend prior to crystallization indeed dictated the resulting lamellar structures, including the average size of lamellar stack and the stack distribution. There seemed to be little variation of lamellar thickness and long period between the two quenching procedures (i.e., single quench versus double quench).

Isothermal crystallization of poly(glycolic acid-alt-6-hydroxyhexanoic acid) studied by DSC and real time synchrotron SAXS/WAXD

The thermal properties and the isothermal hot crystallization behavior of a new regular polyester constituted of glycolic acid and 6-hydroxyhexanoic acid units were studied by differential scanning calorimetry (DSC). The morphological development during isothermal crystallization was also investigated using simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques with synchrotron radiation. A crystalline–amorphous two-phase lamellar system was assumed and interpreted using correlation functions.Kinetic parameters deduced from the Avrami analysis indicated a three-dimensional spherulitic growth from heterogeneous nuclei, whereas optical micrographs revealed the formation of small spherulites with a negative birefringence and a fibrillar texture. The Lauritzen and Hoffman analysis of crystallization regimes was performed taking into account the kinetic constants of the overall crystallization process deduced from DSC and also the reciprocal crystallization halftimes evaluated by means of DSC, SAXS and WAXD experiments. Data were consistent with a single crystallization regime and yielded similar values for the transport activation energy and the nucleation constant in all cases.The evolution of long period and lamellar thickness was evaluated during crystallization. Changes with both crystallization time and crystallization temperature were significant.

Crystallization Kinetics and Crystallization-Induced Morphological Formation in the Blends of Poly(ε-caprolactone)-block-polybutadiene and Polybutadiene Homopolymer

The crystallization kinetics and the perturbation of the melt mesophase induced by crystallization in the blends of a symmetric poly(-caprolactone)-block-poly(1,4-butadiene) (PCL-b-PB) and a poly(1,4-butadiene) homopolymer (h-PB) have been investigated. The crystallization at low to moderate undercooling was found to break out the melt structure and transformed it into a crystalline lamellar structure. The mechanism of the morphological breakout in a cylinder-forming blend with the overall volume fraction of PB (fPB) of 0.78 was resolved by time-resolved simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The results revealed two steps involved in the breakout process. At the initial stage of crystallization, the formation of crystallites within a portion of PCL cylinders deformed the microdomains and initiated local coalescence of the domains through conformational communication of the coronal PB blocks. After this stage the crystallinity started to develop rapidly, and the crystallization was proposed to occur via diffusion of PCL blocks to the crystal growth front, which then induced the formation of extended lamellar morphology. The isothermal crystallization kinetics of the cylinder-forming blend with fPB ) 0.74 was also studied. Interestingly, the overall crystallization rate exhibited an abrupt increase at very large undercooling ( ¢T = 96 K). This anomalous acceleration of crystallization rate indicated that the crystallization kinetics was largely controlled by homogeneous nucleation when the morphological breakout was strongly restricted at very low temperatures.