Towards understanding mesopore formation in zeolite Y crystals using alkaline additives via in situ small-angle X-ray scattering

The formation of micro/mesoporous zeolites by treating zeolite crystals with alkaline hydroxides has received a lot of interest, but fundamental understanding is still lacking. Here, we study the reactivity of a crystalline zeolitic material with various alkaline hydroxides, to close this knowledge gap. The use of ex situ and in situ small-angle X-ray scattering has allowed us to determine the reactivity of faujasite (FAU) type zeolite Y at different pH and Si/Al ratio (SAR), with a variety of different organic ammonium hydroxides. Supplemented with ex situ XRD and BET isotherm measurements, we show that the pH of the starting mixture and SAR of the zeolite significantly influence the stability of the microporous structure and the extent of formation of mesoporous material

Three-body models of breakup and charge-exchange reactions.

We formulate and apply a three-body Glauber model and an adiabatic theory, as alternative approaches to the DWBA method, to study breakup and charge exchange reactions of loosely bound nuclei. The theories derive full finite-range transition amplitudes, which incorporate three-body effects. The formulated Glauber three-body breakup transition amplitude is applied to the (d, pn) deuteron breakup reaction. Three-body s-wave breakup calculations are performed to analyse 260 MeV 63Cu(d, pn) and 270 MeV 12C(d, pn) reaction differential cross-section data. The calculations describe the data fairly well, for low p-n relative energies. The adiabatic theory, in a special limit, is applied to enable computational checks of the Glauber three-body breakup calculations, and for estimation of non-s-wave breakup contributions to the (d, pn) reaction. An adiabatic theory of Coulomb breakup is presented which derives a closed-form adiabatic transition amplitude for Coulomb breakup. Calculations describe deuteron breakup at forward angles at 56, 140 and 270 MeV reasonably well. Previous DWBA analyses are also discussed, and assumptions made in those DWBA calculations are discussed critically. The three-body Glauber model is extended to study the (d, pp) charge-exchange reaction. Three-body effects in the 12C(d, pp)12B reaction are investigated by comparing Glauber calculations with their DWBA limits. The results indicate that these three-body effects are significant and might be responsible for ad hoc modifications needed in DWBA analyses of the same reaction

Effect of Cobalt Fillers on Polyurethane Segmentations Investigated by Synchrotron Small Angle X-Ray Scattering

The segmentation between rigid and rubbery chains in polyurethanes (PUs) influences polymeric properties and implementations. Several models have successfully been proposed to visualize the configuration between the hard segment (HS) and soft segment (SS). For particulate PU composites, the arrangement of HS and SS is more complicated because the fillers tend to disrupt the chain formation and segmentation. In this work, the effect of ferromagnetic cobalt (Co) powders (average diameter 2 μm) on PU synthesized from a reaction between polyether polyol (soft segment) and diphenylmethane-4,4′-diisocyanate (hard segment) was studied with varying loadings (0, 20, 40, and 60 wt.%). The 300 μm thick PU/Co samples were tape-casted and then received heat treatment at 80°C for 180 min. From synchrotron small angle X-ray scattering (SAXS), the plot of the X-ray scattering intensity (I) against the scattering vector (q) exhibited a typical single peak of PU whose intensity was reduced by the increase in the Co loading. Characteristic SAXS peaks in the case of 0-20 wt.% Co agreed well with the scattering by globular hard segment domains according to Zernike-Prins and Percus-Yevick models. The higher Co loadings led to larger deviations from all theoretical models

Morphological structures of poly(n-hexyl isocyanate)-b- poly( -caprolactone) miktoarm star copolymers

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Complex Thin Film Morphologies of Poly(<i>n</i>‑hexyl isocyanate)(5k,10k)–Poly(ε-caprolactone)_1–3(10k,17k) Miktoarm Star Polymers

Two series of crystalline–crystalline miktoarm star polymers were prepared and their thin film morphologies were investigated in detail by synchrotron grazing incidence X-ray scattering (GIXS): poly­(<i>n</i>-hexyl isocyanate)(5000)–poly­(ε-caprolactone)_1–3(17000) (PHIC­(5k)–PCL_1–3(17k)) and poly­(<i>n</i>-hexyl isocyanate)(10000)–poly­(ε-caprolactone)_1–3(10000) (PHIC­(10k)–PCL_1–3(10k)). In addition, their thermal properties were examined. All miktoarm star polymers revealed a two-step thermal degradation behavior where the PHIC arm was degraded first, followed by the PCL arm underwent degradation. Interestingly, all miktoarms were found to show a highly enhanced thermal stability, regardless of their molecular weight over 3k to 17k, which might be attributed to their one-end group capped with the counterpart arm(s) via arm-joint formation. Surprisingly, all miktoarm star polymers always developed only lamellar structure in toluene- and chloroform-annealed films via phase-separation, regardless of the length of PHIC arm as well as the length and number of PCL arm. Despite having highly imbalanced volume fractions, lamellar structure was constructed in the films of miktoarm star polymers through the override of volume fraction rule based on the rigid chain properties, self-assembling characteristics, conformational asymmetry, and compressibilities of PHIC and PCL arms. Furthermore, the orientation of such lamellar structures was controlled by the selection of either toluene or chloroform in the solvent-annealing process. The PHIC arm phases in the lamellar structures favorably formed a mixture of edge-on and face-on structures with fully extended backbone and bristle conformations even under the confined lamellar geometry and arm-joint. The PCL arm phases still crystallized, forming fringed-micelle like structures in which orthorhombic crystals were laterally grown along the in-plane direction of lamellae although their crystallization was somewhat suppressed by the confined lamellar geometry and arm-joint. Overall, crystalline–crystalline PHIC–PCL_1–3 miktoarm polymers demonstrated very interesting but unusual, very complex hierarchical structures in the solvent-annealed thin films