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With the purpose of searching novel, green and energetic oxidants, polynitro-acetone, polynitro-dimethyl ether, and polynitro-dimethylamine are designed as potential powerful oxidants and energetic materials in this work. Their optimized molecular geometries and electronic structures are calculated using density functional theory at m062x/6-311G++(d,p) level. Based on these results, heat of formation (HOF), detonation energy (Q), detonation velocity (D), and detonation pressure (P) are further evaluated. It is found that the oxygen-rich and chlorine-free compounds with 5 to 6 NO2 groups in molecule can be used as the potential energetic oxidants with high oxygen balance, while those with 3 to 4 NO2 groups are suitable for high-density energetic materials. Furthermore, stability correlations of all the compounds are established according to calculated bond order, natural bond orbital (NBO), bond dissociation enthalpies (BDE), and energy gaps (ΔELUMO–HOMO). Finally, burning rate is also calculated to show their potential application as oxidants in propellants. [ABSTRACT FROM AUTHOR]

Nonequilibrium poly(N-isopropylacrylamide) (PNIPAM) chains are generated by temperature-induced conformational transitions in the densely interfacial PNIPAM layer at high adsorbed amounts in aqueous solution. The interleaving chains relax in a spatially heterogeneous space of adsorbed layer which is filled with the domains via the hydrogen bonding and hydrophobic interactions. The relaxation dynamics of interleaving chains is changed from the weekly stretched exponential behaviour at the lower adsorbed amount to the strongly stretched exponential behaviour at the higher adsorbed amount. The kinetic constraints for the relaxation dynamics depend on the segment density of the adsorbed layer which is controlled by the temperature. The stretched exponential relaxation is related to an ensemble of relaxations confined in the domains with different physical origins for the heterogeneous dynamics. The range of energy barriers for the relaxation is estimated from the stretched exponent based on the random first order transition theory. [ABSTRACT FROM AUTHOR]

The effect of two colorant particles with different surface geometries on the stability of shear-induced precursors in isotactic polypropylene was studied after the cessation of shear flow at 140 °C. In the absence of particles, the shear-induced precursors survived for at least 100 s after the shear flow ended. The presence of particles was found to stabilize lower molecular weight chains assisting in the formation of additional shear-induced precursors. The precursors thus formed in the samples containing particles contained two oriented clusters with different molecular weights. Incorporation of lower molecular weight chains in the precursors led to increased dissolution rates of the shear-induced precursors. Particle surface geometry was found to influence precursor dissolution, with planar particles stabilizing the shear-induced precursors to a much greater extent than curved particles. The particles investigated thus act like structural probes to follow quantitatively the dissolution process of precursors after shear and importantly to infer the formation of precursors during shear. [ABSTRACT FROM AUTHOR]

Sheared isotactic polypropylene (iPP) forms a special crystalline assembly called branched shish kebab. The effects of two colorants, Cu-phthalocyanine and ultramarine blue, on the branched shish-kebab structure have been investigated by using synchrotron wide-angle x-ray scattering. The effects of the colorants on the morphological distributions of iPP are well constructed through the shear field or temperature gradient, including crystallinity, molecular orientation, fraction of lamellae, and thickness of crystalline lamellae. It is found that the Cu-phthalocyanine can significantly affect the morphological development of sheared iPP but the ultramarine blue cannot. In the presence of Cu-phthalocyanine, the degree of crystallinity is increased, the molecular orientation is enhanced, the more a*-axis-oriented components form, and the crystalline lamellae are thickened. [ABSTRACT FROM AUTHOR]

We present a new correlation function in the form of γ(r)=r(Df-D) exp(-r/a0)cos(br) to describe the essential features of aggregate structure. The scattered intensity distribution corresponding to this correlation function was obtained. Compared with existing models, the new scattering formula can predict a scattering peak in a finite wavevector and control the scattered intensity decay in larger wave vectors. The experimental scattering patterns obtained from polydimethylsiloxane/paraffin liquid mixtures were tested well by the new model. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Theeffect of sodium dodecyl sulfate (SDS) on the poly(N-isopropylacrylamide) (PNIPAM) tethered to nanoparticles was experimentallyinvestigated using dynamic light scattering below the lower criticalsolution temperature. A mean-field analytical model was used to calculatethe parameters of interfacial PNIPAM–SDS complexes. Particularly,the magnitude of SDS adsorption energy obtained decreases with decreasingexcluded volume parameter, implying that the partially collapsed PNIPAMbrush virtually favors the adsorption of SDS onto the PNIPAM chains.A self-consistent field theory (SCFT) model was used to get a detailedquantitative description of monomer density distribution. By loweringthe solvent quality, a number of phenomena related to the noncontinuityof monomer density are revealed. These phenomena are either referredto as the vertical phase separation or as its precursor, which canbe delayed and eventually eliminated as the SDS coverage is increased.The distribution of free chain ends was calculated using the SCFTmodel. Increasing the SDS coverage gives rise to a broader and moreasymmetric distribution of free chain ends, accompanied by a considerableexpansion of the dead zone (below which the free chain ends do notexist), but lowering the solvent quality has opposite influences.The relative thickness of the dead zone can be scaled to a mastercurve, regardless of SDS coverage. [ABSTRACT FROM AUTHOR]

Abstract: Here, we report the fabrication of a well inter-grown ZIF-8 membrane on coarse α-Al2O3 support via a two-step hydrothermal synthesis method. The ZIF-8 seeds were initially vacuum seeded to ensure overall coverage of the voids on the α-Al2O3 support followed by hydrothermally treated twice for forming well inter-grown membrane. The presence of sodium formate was found to be of critical importance to enable the growth of ZIF-8 structure into a continuous membrane. This method enabled our ZIF-8 membrane to exhibit CO2 permeance of 3.49×10−7 mol/m2 sPa with significant CO2/N2 and CO2/CH4 selectivity of 3.4 and 4.0, respectively. [Copyright &y& Elsevier]

• Direct electrochemical C2 phosphonylation of thiazole derivatives under mild conditions. • The avoidance of external metal, additive and chemical-oxidant. • Facile access to various phosphorus compounds containing multi heteroatoms. • An atom economic system with simple operation and wide substrate scope. We herein report a direct electrochemical dehydrogenative C H phosphonylation of thiazoles derivatives with H 2 evolution. Employing electricity as the green and sole oxidant, cheap metal as electrode, the anodic oxidation together with cathodic hydrogen evolution process provides a green and efficient strategy for C H phosphonylation. A diverse range of phosphorus products were constructed under external metal and oxidant-free conditions at ambient temperature, featuring atom economy, simple operation and wide reaction scope. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The present study presents a method to predict the flow distribution imposed on an injection moulded melt crystallised isotactic polypropylene (iPP) from its experimentally determined morphological distribution. A microrheological model, based on the Doi–Edwards model, was used to calculate the flow-induced free energy for the flow-induced crystallisation. The low limit flow field required to generate the final structures was then obtained. The effect of Cu-phthalocyanine (CuPc), a nucleating agent, on the flow history was also studied. Instead of geometric positions, structural parameters such as molecular orientation and crystallinity were correlated to the flow history of the injection-moulded iPP. The work provides a simple approach to predict flow–structure relationships for complex thermo-mechanical processing treatments, which can then guide the realistic design and control of the flow-induced crystallisation of polymers. [Copyright &y& Elsevier]

Abstract: The morphology of isotactic polystyrene (iPS) particles which had been compounded into an isotactic polypropylene (iPP) matrix was varied in-situ by selective heat treatment to be either amorphous (iPSamorphous) or semicrystalline (iPScrystalline). The influence of iPS morphology on the quiescent and shear-induced isothermal crystallisation of iPP was then studied using differential scanning calorimetry (DSC), in-situ simultaneous small and wide angle X-ray scattering (SAXS/WAXS) and polarised optical microscopy (POM). In the quiescent condition iPScrystalline was found to selectively nucleate the β phase while iPSamorphous nucleated the α phase of iPP. Compared to the control sample (iPPcontrol), the presence of both morphologies of iPS increased the number of shear-induced oriented crystal precursors that form as a result of the step shear. During isothermal crystallisation the shear-induced nuclei promote oriented α form crystal growth, accelerate the crystallisation kinetics and ultimately swamp the effect of the nucleating particles present. [Copyright &y& Elsevier]

The molecular and lamellar orientations of injection-moulded isotactic polypropylene were investigated using simultaneous wide- and small-angle X-ray scatterings. In order to obtain the meaningful degree of molecular orientation with respect to the flow direction, the axis orientations of parent and daughter lamellae were separately calculated. The molecular orientation of thin material is consistent with the lamellar orientation. However, the decrease in the lamellar orientation of thick material is associated with a constant degree of molecular orientation, which would indicate an intra slip between parent lamellae along the flow direction. [ABSTRACT FROM AUTHOR]

Abstract: Small-angle X-ray scattering (SAXS) studies were carried out to investigate effects of sodium benzoate (SB) on the shear-induced distributions of lamellar structures through the depth direction of injection-moulded isotactic polypropylene (iPP) plates, using the micro beam available from a synchrotron to gain good spatial resolution. It was found that in the presence of SB, the shish–kebab structure emerges over a broader range to include regions in which a random arrangement of crystalline lamellae is found without SB. The oriented crystalline lamellae are even found in positions that are very close to the core center. The SB-induced shish–kebab structure under low levels of shear flow is attributed to lower free energy barriers for the coil-to-stretch transition and shorter times to start the crystallization. The effect of SB on the lamellar dimensions is significant only in the core region, and only when the concentration of SB is sufficiently high. A down-U distribution of the long spacing is found, which is mainly ascribed to the variation of thickness of crystalline lamellae with the depth. The results show that a higher level of lamellar orientation is not necessarily accompanied by a higher degree of linear crystallinity. [Copyright &y& Elsevier]

Synchrotron small-angle X-ray scattering (SAXS) studies were carried out to investigate effects of thickness of injection-moulded isotactic polypropylene (iPP) plates on shear-induced morphology and morphological distribution through the depth direction of the plates. Different levels of effective shear flow are imposed on the iPP melt by changing the thickness of the plates although the injection moulding is performed with the same injection ram speed and the same melt and mould temperatures. Shish-kebab-like morphology is found roughly 100 μm from the surface of plates, regardless of the thickness of plates. However, the type of shish-kebab-like morphology is very sensitive to the thickness. The shish-kebab structure at the surface region can be changed into the kebab-structure only or random crystalline lamellae as the thickness of the plate increases. The preferential orientation of crystalline lamellae along the flow direction strongly depends on the thickness of the plate, although the melt-shear does not significantly enhance the degree of linear crystallinity. It is also found that in the core region, the slow relaxation of polymer chains in the thick plate results in a higher degree of linear crystallinity. The results indicate that the shear-induced morphology is strongly dependent on effective shear flow and should be described individually. [Copyright &y& Elsevier]

Zeolite W membranes were grown on their seed pellets prepared via a straightforward vacuum filtration method followed by crystallization, rendering them self-supported. Herein, the feasible application of self-supported zeolite W membranes for CO2/CH4 separation with astonishing CO2/CH4 selectivity was demonstrated. [ABSTRACT FROM AUTHOR]

This study explored the combined influence of shear flow and nucleating agents on isotactic polypropylene (iPP) crystallisation. The study showed that oriented α-iPP crystals were not necessary to form β-iPP crystals, contrary to the accepted view that the surface of oriented α-iPP crystals provides nucleation sites for an α-iPP to β-iPP growth transition. Instead it was proposed that flow-induced mesomorphic point-like nuclei preferentially nucleates β-iPP. The combined effect of shear flow and nucleant was found to promote γ-iPP crystals. The surprising γ-iPP nucleation effect was explained by the high density of flow-induced and heterogeneous nuclei present at the start of crystallisation. [ABSTRACT FROM AUTHOR]