Electron microscopy of oriented high-density polyethylene: Comparison with small-angle X-ray scattering

The morphology of cold-drawn, rolled and annealed high-density polyethylene was investigated by transmission electron microscopy of stained sections. From the electron micrographs, a model of the structure was developed and the scattering pattern calculated. This was then compared with the corresponding small-angle X-ray scattering (SAXS) pattern, in order both to aid in the interpretation of SAXS patterns of oriented polymers, and to assess the effects of staining with chlorosulphonic acid on the morphology.     

Structure development during isothermal crystallisation of high-density polyethylene: Synchrotron small-angle X-ray scattering study

Isothermal melt crystallisation in high-density polyethylene (HDPE) was studied using the time-resolved SAXS method with synchrotron radiation over a wide range of crystallisation temperatures. The SAXS profile was analysed by an interface distribution function, g₁(r), which is a superposition of three contributions associated with the size distributions of crystalline (L_C) and amorphous (L_A) layers and a distribution of long period (LP). The morphological parameters extracted from the g₁(r) functions show that the lamellar thickness increases with time, obeying a logarithmic time dependence. The time evolution of L_C observed for the sample crystallised at 122 °C leads to the conclusion that crystallisation proceeds according to the mechanism of thickening growth. For samples crystallised at lower temperatures (116 °C and 118 °C), the lamellar thickening mechanism has been observed. The rate of lamellar thickening in these cases is much lower than that at 122 °C. At 40 °C, thickening of the crystalline layer does not occur. The interface distribution functions were deconvoluted, and the relative standard deviation σ_C/L_C obtained in this way is an additional parameter that is varied during crystallisation and can be used for analysis of this process. Time-dependent changes in the σ_C/L_C at large supercooling (T_C=40 °C) indicates that L_C presents a broad distribution in which the relative standard deviation increases with time. At lower supercooling (T_C=122 °C), L_C shows a much sharper distribution. In this case, the relative standard deviation decreases with time.     

Crystallization behavior of polylactide on highly oriented polyethylene thin films

The crystalline structure and morphology of the PLA crystallized isothermally from the glassy state on highly oriented PE substrates at 130℃were investigated by means of optical microscopy,AFM and X-ray diffraction.The results indicate that the PE substrate influences the crystallization behavior of PLA remarkably,which leads to the growth of PLA crystals on PE substrate always in edge-on form rather than the twisted lamellar crystals from edge-on to flat-on when crystallizing the PLA on glass surface under the same condition.The edge-on PLA lamellae on the PE substrate are preferentially arranged with their long axes in the chain direction of the PE substrate crystals.It is further demonstrated that except for the different crystal orientation,the PE does not influence the crystalline modification and crystallinity of the PLA.     

Small-angle X-ray scattering study on the microstructure evolution of zirconia nanoparticles during calcination

Zirconia nanoparticles have been synthesized from zirconium hydroxide precipitates followed by a supercritical CO₂ extraction. The microstructure evolution of these zirconia nanoparticles during the calcination at the moderate temperature has been investigated. Assisted by the analyses of TEM and XRD, small-angle X-ray scattering (SAXS) study offers possibilities to a comprehensive and quantitative characterization of the structural evolution on the nanometer scales. The as-synthesized zirconia sample exhibits a mass fractal structure constructed by the surface fractal particles. Such a structure can be preserved up to 300 °C. After calcination at 400 °C, considerable structural rearrangement occurs. In the interior of nanoparticles zirconia nanocrystallites emerge. It is the scattering from such zirconia nanoparticles that give rise to the broadened crossover in the ln[J(q)] vs. ln q plot and the scattering peak in the ln[q³J(q)] vs. q² plot. With a further increase in the calcination temperature, the power-law region at large-q in ln J(q) vs. ln q plot expands, and the peak in ln[q³J(q)] vs. q² plot shifts towards lower q values, indicating size increases in both the nanocrystallites and nanoparticles. Besides, the mass fractal structure constructed by zirconia nanoparticles can be largely preserved during the moderate temperature calcination.     

Ultra-small-angle X-ray and neutron scattering study of colloidal dispersions

The ultra-small-angle X-ray and neutron scattering techniques are useful techniques for the investigation of colloidal systems. The very high small-angle resolution of these scattering techniques has provided important and novel information to elucidate the formation mechanism of colloidal crystals. The Bonse–Hart optical system is expected to become a standard tool for investigating mesoscopic structures.     

Conformational analysis of oriented non-crystalline polymers using wide angle X-ray scattering

A procedure is presented for obtaining conformational parameters from oriented but non-crystalline polymers. This is achieved by comparison of the experimental wide angle X-ray scattering with that calculated from models but in such a way that foreknowledge of the orientation distribution function is not required. X-ray scattering intensity values for glassy isotactic poly(methylmethacrylate) are analysed by these techniques. The method could be usefully applied to other oriented molecular systems such as liquid crystalline materials.     

Structural evolution of melt-drawn transparent high-density polyethylene during heating and annealing: Synchrotron small-angle X-ray scattering study

The morphological development of melt-drawn transparent high-density polyethylene during heating was investigated employing in-situ synchrotron small-angle X-ray scattering (SAXS) technique. The results confirm that at lower temperatures only meridional scattering peaks aligned perpendicular to the extensional flow direction can be observed, indicating a highly oriented lamellar crystallite structure; whereas at higher temperatures an equatorial streak additional to the layer-like meridional scattering pattern develops, reflecting the presence of shish-kebab-like objects in the specimen under investigation. Upon heating, the average thickness of the kebab crystals remains essentially unaffected below 110 °C, and subsequently the selective melting of the less stable kebabs proceeds yielding thicker layered lamellar crystals. When the temperature is raised to 131 °C, the shish-like formation and the thermally stable kebab crystals melt simultaneously. In addition, the microstructure of the melt-drawn specimen subjected to annealing at elevated temperatures was probed at room temperature. As opposed to the SAXS patterns registered at high temperatures, the SAXS diagram measured after annealing shows no equatorial streak, suggesting that the cylindrical structures could be re-formed. This observation can be explained by assuming that the plate-like kebab crystals with their normal parallel to the stretching direction grow and impinge during cooling to room temperature due to secondary crystallization, which can be verified by in-situ SAXS experiments during annealing and subsequent cooling.     

A small-angle X-ray scattering study of bromine-containing latex particles

A small-angle X-ray scattering (SAXS) study of two-stage latices (TSL), composed of polystyrene (PS) and polytribromostyrene (PTBrS), is presented. The analysis of the scattering curves leads to the conclusion that the TSL particles have a concentric core-shell structure. When a PTBrS latex was used as a seed, its particles were overcoated with a PS shell during the second-stage polymerization. However, only a small portion of the seed particles were overcoated with a PTBrS shell when using a PS seed. The size distributions of the TSL and the PTBrS latex particles were determined from the scattering curves, using the method of Indirect Fourier Transformation. The resulting average radii were in good agreement with the values obtained from TEM observations. © 1996 John Wiley & Sons, Inc.     

基于同步辐射超小角X射线散射的高密度聚乙烯空洞化行为研究

以一系列高温结晶后自然冷却的高密度聚乙烯(HDPE)为研究对象,利用同步辐射超小角X射线散射(USAXS)和示差扫描量热技术(DSC)对样品的微观结构进行了分析,并在线研究了单轴拉伸过程中的空洞化行为.结果表明,结晶温度高于110℃后自然冷却到室温的样品中存在热稳定性不同的两组片晶,等温过程形成结构完善的厚片晶,而在冷却过程会形成有缺陷的薄片晶,两组片晶的熔点分别在133和110℃附近.在30℃拉伸时,所有样品都可观察到空洞化并伴随发白现象.并且,等温结晶中形成片晶厚度越大的样品,相应的空洞化现象越明显.在拉伸过程中,空洞出现在屈服点附近,其法向方向平行于拉伸方向,后随应变的增加发生转向,法向方向与拉伸方向垂直.样品中空穴的长度为900~1200 nm.另一方面,随着冷却过程生成薄片晶比例的增加,空洞化趋势下降.此外,提高拉伸温度,样品更倾向发生塑性形变,空洞化程度减弱.     

On the interpretation of small-angle X-ray scattering during water adsorption by carbon adsorbents

Two models accounting for the changes of shape of the small-angle X-ray scattering (SAXS) curves during water adsorption by carbon adsorbents are discussed. The first model is based on the assumption of partial filling of the pore space; the second one presumes micropore swelling during water adsorption. Analysis of the results allows one to conclude that the first model is valid. This conclusion is in agreement with adsorption investigation data.Deseased 1993.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1220–1223, July, 1993.     

Growth process for fractal polymer aggregates formed by perfluorooctyltrimethoxysilane. Time-resolved small-angle X-ray scattering study

The acid-catalyzed condensation reaction of perfluorooctyltrimethoxysilane (PFOS) and n-octyltrimethoxysilane (OTMS) in ethanol has been followed by time-resolved synchrotron radiation small-angle X-ray scattering (SAXS) on a short time scale. SAXS curves for PFOS and OTMS have been interpreted as arising from mass fractals with D _f=2 (PFOS) and D _f=1.7 (OTMS). The time dependence of the apparent radius of gyration, obtained from the Guinier plots, showed that the growth of fractal precursors occurs in a two-step process within 2 h for PFOS and within 1.5 h for OTMS, in which small clusters involving monomers, dimers and trimers are formed in the initial step and formation of larger clusters occurs in the second step. Furthermore, it has been suggested that the hydrophobicity and lipophobicity of the bulky alkyl groups may also contribute to the formation of these giant aggregates. Received: 13 July 1999/Accepted in revised form: 6 October 1999     

A small-angle X-ray scattering study of nanoparticle assembly in an aligned nematic liquid crystal

The assembly of colloidal particles in a nematic liquid crystal has been investigated using small-angle X-ray scattering. The structure and orientation of nanoparticle assemblies in bulk samples of aligned nematic liquid crystal have been determined. The method offers some advantages over optical microscopy, which is usually restricted to investigations of thin cells and micron-sized particles. The scattering from chains of particles has been calculated, and comparison with experimental results has shown that suspensions of 48 and 105 nm diameter silica nanoparticles formed highly ordered structures perpendicular to the liquid crystal director, consistent with quadrupolar defect-induced assembly.     

Alkoxy-derived multiscale porous TiO<Subscript>2</Subscript> gels probed by ultra-small-angle X-ray scattering and small-angle X-ray scattering

Titania (TiO₂) monoliths with well-defined bicontinuous macropores and gel skeletons were prepared through the alkoxy-derived sol–gel process accompanied by spinodal decomposition, and the structural evolution during evaporation drying and heat treatment was probed by a combination of ultra-small-angle X-ray scattering and small-angle X-ray scattering. X-ray scattering profiles of wet and dried gels revealed that microporous structures related to the existence of primary particles are present in the gel skeletons at the wet stage and are preserved during drying. Additionally, it is found that the primary particles swollen in the wet condition are dried to compact aggregates to produce the smooth surface of gel skeletons. Upon heating at 400 °C, the particle–particle correlation associated with regularity of mesostructures is enhanced. From nitrogen adsorption–desorption measurements, the average pore size is less than 1 nm in the dried gel and increases to 3.1 nm by the heat treatment. Homogeneous growth of primary particles due to interparticle-polycondensation reaction is responsible for the increased size and uniform distribution of mesopores in the heat-treated gel.     

Investigation of structural changes in semi-crystalline polymers during deformation by synchrotron X-ray scattering

The mechanical behavior of polymer materials is strongly dependent on polymer structure and morphology of the material. The latter is determined mainly by processing and thermal history. Temperature-dependent on-line X-ray scattering during deformation enables the investigation of deformation processes, fatigue and failure of polymers. As an example, investigations on polypropylene are presented. By on-line X-ray scattering with synchrotron radiation, a time resolution in the order of seconds and a spatial resolution in the order of microns can be achieved. The characterization of the crystalline and amorphous phases as well as the study of cavitation processes were performed by simultaneous SAXS and WAXS. The results of scattering experiments are complemented by DSC measurements and SEM investigations. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1574–1586, 2010     

Resonant soft X-ray scattering in polymer science

Resonant soft X-ray scattering (RSoXS) is an emerging, powerful technique to probe the nano-to-mesoscale structure of polymers and other molecules. It joins together small-angle X-ray scattering (a statistical nanoprobe) with X-ray spectroscopy that brings with it unique chemical and bond-orientation sensitivity. Through over a decade of discovery and development, RSoXS is moving from a niche technique applied to organic electronic thin films to a mature tool applicable to a plethora of polymeric and molecular systems, encompassing new modalities, analyses, and simulation methods. This development promises to deliver increasingly quantitative answers to challenging questions in polymer science as well as expand its usefulness to complementary fields. This review presents a full synopsis of the technique, including background on the theoretical underpinnings, measurement best practices, and examples of recent RSoXS applications and discoveries provided here to accelerate the transition to a broader range of soft matter and polymeric fields.     

Effect of ultrasound on the microstructure of polystyrene in cyclohexane: a synchrotron small-angle X-ray scattering study

Synchrotron small-angle X-ray scattering technique has been used to study the effect of ultrasound on the microstructure of polystyrene (PS) in cyclohexane solutions. The results show that the intramolecular radius of gyration (R _g) decreases with ultrasound, indicating the shrinkage and collapse of PS chains. There is an exponential relationship between R _g and the molecular weight of PS (M _w), and the exponent changes from 0.5 to 0.417, as the ultrasound time is increased. This means that the shape of PS chain changes from random coil to shrunken form. The Kratky plots also confirm the shape transformation of PS chains induced by ultrasound. Moreover, the intermolecular correlation length increases with the ultrasound time, which is indicative of the entanglement of PS chains.     

High brilliance small-angle X-ray scattering applied to soft matter

This article reviews some recent applications of high brilliance small-angle X-ray scattering (SAXS) to soft matter and closely related systems in biology. Owing to the burgeoning literature in this field, examples presented are restricted to those exploiting the high brightness of the synchrotron source. Three types of experiments are discussed; (1) dynamic processes in systems driven out of equilibrium, (2) transient processes in extremely dilute systems, and (3) microbeam technique probing the local nanostructure of hierarchically organized specimens. In addition, recent advances in sample environments specifically adapted to microbeam applications are described. Present limitations and suggestions for future developments are discussed.     

Morphology development during the polymerization of styrene within a polyurethane network: Investigations by small-angle X-ray and light scattering

Phase separation that takes place during the formation of semi-interpenetrating polymer networks based on crosslinked polyurethane and linear polystyrene was studied by small-angle X-ray scattering and light scattering. The kinetics of the chemical reactions was followed by Fourier transform infrared spectroscopy. The occurrence of broad peaks in the X-ray scattering curves was interpreted in terms of distances between the urethane crosslinks. Small modulations on these curves were assigned to sphere-like structures with a diameter of around 5 nm which might be related to the urethane crosslink regions. Small modulations on the light-scattering curves at the beginning of styrene polymerization were assigned to spheres with diameters of around 4.5 μm, which can be related to the polystyrene-rich phase. These modulations disappear with time, which might indicate an increasing polydispersity of the domain sizes. The final morphology was found to depend on the time at which polymerization of styrene is initiated with respect to the time of gelation of polyurethane.     

The exponential distribution in small angle X-ray scattering. Theory and practice

Summary From all the theoretical small-angle X-ray scattering (SAXS) curves of compact (non-particulate) systems elaborated systematically by Porod [2], we give a theoretical analysis of only one scattering curve, the corresponding correlation function of which is an exponential distribution. To obtain a correct as well as an easier determination of the zero-intensityI ₀ and the correlation lengthl _c than with the procedure usual up to now (analysis of the plotI(s)^–1/n vs.s ² withn=2 or 3/2) the classical SAXS-parameters of particle scattering will be involved in the evaluation. In this way the results get also a more useful conception for a practical application.Von den systematisch besprochenen Röntgenkleinwinkelstreukurven der dichtgepackten Systeme von Porod [2] wird nur eine Streukurve, deren Korrelationsfunktion eine exponentielle Verteilung aufweist, theoretisch analysiert und mit den klassischen Auswertungsmethoden der Partikelstreuung in Verbindung gesetzt. Dadurch werden die die Streukurve bestimmenden Parameterl _c (Kohärenzlänge) und die NullintensitätI ₀ besser erfaßt als mit der in der Literatur bisher veröffentlichten Methode (AuftragungI(s)^–1/n gegens ², mitn=2 oder 3/2). Damit erhalten außerdem die Meßergebnisse eine anschaulichere Auslegung.Dedicated to Prof. Dr. Dr. h.c. mult. Otto Kratky on the occasion of his 90th birthday