The ability to measure small deformations or strains is useful for understanding many aspects of materials. Here, a new analysis of speckle diffraction peaks is presented in which the systematic shifts of the speckles are analyzed allowing for strain (or flow) patterns to be inferred. This speckle tracking technique measures strain patterns with a accuracy similar to x-ray single crystal measurements but in amorphous or highly disordered materials.

Two-time correlations determined by XPCS display anisotropic and heterogeneous dynamics in a stretched silanized silica-elastomer nanocomposite (time scale 70 minutes).

ABSTRACTTensile stress‐relaxation measurements have been performed on a series of cross‐linked filled elastomers. The fillers are chosen to investigate the effect of the filler–filler and the filler–matrix interactions on the time dependence of the tensile relaxation modulus E(t) after UP and DOWN jumps. For the carbon black‐filled sample (strong filler–elastomer interaction) E(t) decreases as log(t) when the strain ε is strictly larger than 0.2 and reached by UP jumps. For the silica‐filled samples in the same conditions, and for all samples after a DOWN jump, including ε = 0.2, the experimental data can be fitted with a power law equation characterized by the exponent m. Thus, in all cases, |dE(t)/dt| scales as t−α with α ⩵ m + 1. Pertinence of the soft glassy rheology model for interpreting these results is examined. It is shown that α could be equivalent to the effective noise temperature x and related to the polymer chain mobility. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 647–656

The complexity of the mechanical behavior of filled elastomers can be partly attributed to the fact that the duration of an applied strain plays a crucial role. In order to bring new insights into this still incompletely solved problem, we look for relationships between the macroscopic mechanical relaxation and the relaxation of the filler particles at the nano-to mesoscale. To this end, X-ray photon correlation spectroscopy (XPCS) in homodyne and heterodyne configurations combined with tensile stress relaxation is employed. The paper is devoted to the study of the role of the filler filler and the filler matrix interactions in a cross-linked,elastomer on the aging mechanisms under strain. The fillers investigated are carbon black, as an example of strong filler matrix interactions, and hydroxylated silica for which the filler filler interaction is strong (H-bonds). Homodyne XPCS correlation reveals features of jammed systems (compressed exponential and ballistic motion) for both systems. The exponents characterizing the aging of the homodyne relaxation times are not the same in the carbon black and in the silica filled samples. For both systems, the decrease of the particle velocity determined by heterodyne detection with aging time follows a power law. The silica sample is characterized by a slow decrease of the velocity during aging. For the carbon black sample, the velocity remains small and decreases faster than for the silica sample. The reverse is observed for the behavior of the tensile force.

The temperature-induced structural modifications of poly(N-isopropylacrylamide) hydrogel (pNIPA) were investigated by small-angle X-ray scattering (SAXS) over a broad range of q values (3.5 x 10(-2)-12 nm(-1)) at temperatures ranging between 18 and 37 degrees C. The sample Studied was claborated by cryopolymerization yielding a macroporous gel (cryogel). The pNIPA gel forms the walls (the thickness at 23 degrees C is about 12 mu m). The SAXS curves display an isoscattering (or isosbestic) point located at q(iso) = 3.633 nm(-1) and disappearingabovc 30 degrees C. This feature has never been reported up to now. The SAXS curves obtained at each temperature are well fitted by a sum of four equations describing respectively the scattering resulting from the gel surface (power law), from the solidlike (Guinier equation) and liquidlike (Ornstein - Zernike equation) heterogeneities, and from the chain-chain correlation yielding a broad peak (pseudo-Voigt equation) in the high-q domain. The temperature dependence of the parameters obtained from the fit is analyzed and discussed.

The structural modifications induced by changes in temperature are investigated by Small-Angle X-ray Scattering (SAXS) over a broad range of q-values (3.5×10-2 – 12 nm-1) in cryogels based on N-isopropylacrylamide (NIPA) and/or 2-Hydroxyethyl methacrylate-L-Lactide-Dextran (HEMA-LLA-D) macromer. Various copolymeric cryogels of these two monomers are prepared by cryopolymerization yielding macroporous gels (cryogels). For the plain pNIPA cryogel, the SAXS curves obtained at each temperature are well fitted by a sum of four equations describing respectively the scattering resulting from the gel surface (power law), from the solid-like (Guinier equation) and liquid-like (Ornstein-Zernike equation) heterogeneities and from the chain-chain correlation yielding a broad peak (pseudo-Voigt equation) in the high-q domain. The temperature dependence of the parameters obtained from the fit is analyzed and discussed. It is shown that the existence of an isoscattering (or isosbestic) point observed in pNIPA gels and in some copolymers is related to features observed by Differential Scanning Calorimetry and swelling ratio measurements.

Two-photon fluorescence microscopy (TPFM) usually used to get 3-D pictures of biological systems has been applied here for the first time to macroporous hydrogels prepared by cryogelation ("cryogels"). Unlike environmental scanning electron microscopy (ESEM) which analyzes the Surface of swollen samples, TPFM delivers images of successive planes in the depth of the material allowing a 3-D imaging of its structure. The macroporous hydrogels studied were poly(N-isopropylacrylamide) (pNIPA), poly(hydroxyethyl methacrylate-L-lactide-dextran) (pHEMA-LLA-D) and various copolymeric gels of these two ones. A quantification of the macropore size distribution and the wall thickness and their modification with respect to the ratio NIPA/HEMA-LLA-D or to the temperature, in the case of pNIPA, was readily obtained.

The meso- and nano-structure of thermosensitive macroporous polymers ("cryogels") is investigated by SAXS, showing that the nanostructure of the sample is related to swelling.

XPCS with heterodyne detection (HD-XPCS) is a new original method that gives information about the dynamics of filler aggregates during stress relaxation and its relation to the macroscopic mechanical behavior measured in situ.

The mesophase behaviour of a side‐chain liquid crystalline polyacrylate (LCP) grown by drying a solution has been investigated. This LCP, characterised by a short spacer (four carbon atoms) and a long tail (10 carbon atoms), displays, at increasing temperatures, SmC and SmAd phases. The effect of the mean molecular weight, i.e. the mean number of side chains per polyacrylate main chain (18 and 51) on the lamellar width, was studied. LCP–silica nanocomposites have been synthesised by a sol‐gel process in the presence of LCP in the solution, followed by subcritical drying. The mesophase behaviour of these nanocomposites was compared to that of the corresponding bulk LCP. The experimental methods were polarised optical microscopy, differential scanning calorimetry and synchrotron X‐ray scattering.

Small-angle X-ray scattering (SAXS) performed down to small q values (q <or= 10(-3) A(-1)) is a powerful method for investigating the arrangement of filler aggregates in filled elastomers under uniaxial strain. Meanwhile, for vulcanized samples, zinc oxide is used as an additive. Owing to their high contrast, the ZnO particles remaining in the manufactured composite are strong X-ray scatterers. In the low-q domain, their scattering hides that of filler aggregates (carbon black, pyrogenic silica) and must be quantified in order to be suppressed. To this end, anomalous SAXS (ASAXS) and small-angle neutron scattering (SANS) have been performed. It is shown that ASAXS measurements can be performed down to small q values (q <or= 10(-3) A(-1)). Therefore ASAXS is well adapted to separate the contributions of ZnO and filler scattering. For neutron scattering the contrast of the ZnO particles is similar to that of carbon. Because the amount of ZnO is much smaller than that of filler, ZnO scattering can be neglected. Owing to multiple scattering effects, however, SANS can only be used for very thin samples (less than about 0.25 mm). It is shown that, providing multiple scattering is avoided, ASAXS and SANS yield similar scattering curves for the filler aggregates.

Carbon aerogels are very promising substrates for electrocatalyst deposition involved in fuel cells. Their advantage over high surface area carbon blacks currently used, is the porous monolithic structure yielding large pore volumes with controlled pore sizes. By changing the synthesis parameters, it is possible to adjust their multi-scale structure which is strongly related to the electrochemical performances. The aim of the lecture is to give a survey of information about the multi-scale structure that can be obtained by small and wide angle X-ray scattering (SAXS and WAXS) techniques combined with contrast variation (CV). To this end, a series of SAXS experiments on carbon aerogels are described and the analysis of the experimental data is explained. Particular attention is paid to the determination of the specific surface area, SSAXS, and to the reasons why WAXS curves combined to SAXS ones make this determination more pertinent. The physical meaning of similarity or difference between SSAXS and surface area determined by gas adsorption, SADS, is discussed and information obtained by using contrast variation (CV) is described for two carbon aerogels prepared in different conditions.

Mesostructured carbon materials were obtained by nanocasting MCM-48 and SBA-15 ordered mesoporous silica templates via two carbon infiltration routes: a liquid-phase process (LPI) using sucrose solution or a gas-phase chemical vapor infiltration (CVI) process using propene. The structural characteristics of the carbon replicas were investigated by synchrotron low-angle X-ray diffraction (LAXRD) analysis in combination with transmission electron microscopy (TEM). The materials obtained by the liquid-phase process demonstrated a long-range mesoscopic order at relatively low carbon loading (ca. 35 wt % in SiO2/C composite), with their structural elements being essentially shrunk compared to that of the templates. The CVI replicas at similar low infiltration content were found to be only partly organized within nanodomains, but at bigger carbon loading (ca. 50 wt %) highly ordered mesostructures displaying up to ten nonzero XRD reflections were obtained. Moreover, these materials were shown to have thicker frameworks faithfully replicating their templates. Particular features of the CVI replica of MCM-48 were an amorphous carbon shell on the external particle surface and a gradient of the nanoframework displacement. The carbon replicas of SBA-15 were characterized by a semitubular structure.

Small angle neutron and x-ray scattering methods are used to investigate the structure of dilute suspensions of two different ferrofluid systems dispersed in soft polyacrylamide hydrogels. It is found that the particles in the fluid are fractal aggregates composed of smaller particles of radius ca. 5 nm. The fractal dimension is strongly dependent on sample, taking the value 1.7 in the first sample and 2.9 in the second sample. In the presence of a magnetic field the aggregates orient, but are restricted in both their translational and rotational freedom. The effect of the gel elasticity is treated as a hindrance to the orientation process.

Carbon black is widely used as a filler in order to modify the mechanical or the electrical properties of polymers. Such composites display significant non-linear effects. Moreover, examination of the large number of papers devoted to the physical properties of carbon black filled polymers indicates that each composite, even composites apparently consisting of similar matrixes and similar carbon blacks, may behave differently when prepared by different mixing methods. The present work aims to show that these particular behaviors can be related to the fact that carbon blacks used for composites are mass fractals of low dimensionality (D f <2) that are able to interpenetrate each other to an extent that depends on the filler-matrix surface interaction and on the volume fraction of filler. Small-angle X-ray scattering (SAXS) is a convenient method for studying disordered systems at length scales ranging between a few tenths and a few hundred nm. SAXS is therefore particularly advantageous for exploring the morphology of carbon black aggregates and their degree of interpenetration when dispersed in a matrix. Furthermore, the use of an area detector yields two-dimensional images and hence information about anisotropy of the arrangement of scatterers. It is shown that this arrangement profoundly influences the physical properties of the composites. Analysis of SAXS curves obtained for a rubber grade carbon black (N330) and for composites prepared by dispersing it into polyethylene or EPR will be presented. As an example, the temperature and frequency dependence of the electrical conductivity will be discussed and compared to theoretical models. Finally, the mutual consistency of the electrical and mechanical behavior, theoretical models and information deduced from the scattering curves will be shown.

Carbon blacks (CE) demonstrate varied structural features on length scales from angstroms to micrometers. Widely used as fillers in polymers, carbon blacks improve the mechanical and electrical properties of the host material. In general, CB is a low-dimensional mass-fractal aggregate of carbonaceous primary particles. Here we investigate the effect of processing on the interpenetration of aggregates in CB/polymer composites by small-angle X-ray scattering (SAXS). We performed SAXS measurements on a series of N330/EPR and N330/HDPE composites containing different amounts of a commercially available N330 carbon black. N330/HDPE composites were prepared by two different methods. The first method is Brabender dispersion of depelletized N330 in molten polymer; the second method is high-shear mixing of depelletized N330 in HDPE dissolved in a good solvent and subsequent addition of this mixture to a poor solvent for polyethylene. SAXS experiments were performed at the University of New Mexico/Sandia National Laboratories SAXS Laboratory. Data were collected on the Bonse-Hart camera with a a-range of 0.003 < q < 1 nm(-1). This wide q-range probes the structure of both the primary carbon black particles and aggregates of these particles. Depelletized N330 displays two power law regimes from which we deduce a surface-fractal dimension D-s = 2.3 for the primary particles and a mass fractal dimension D-m = 1.8 for the aggregate. For pelletized N330, the mass fractal domain vanishes as a result of aggregate interpenetration and, therefore,loss of correlation between primary particles. For N330/HDPE composites prepared by the Brabender method, the SAXS curve is similar to that obtained for the depelletized samples, indicative of little to no interpenetration of the aggregates. For N330/HDPE composites prepared by the solvent method and N330/EPR composites the SAXS curve is similar to that obtained for pelletized N330, indicative of extensive interpenetration of the aggregates.