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Aqueous solutions of polyethylene glycol are studied by small-angle neutron scattering over a broad range of polymer molecular masses and concentrations. The scattering data were modeled by a Gaussian chain form factor combined with random phase approximation, which provided good fits over the whole studied concentration range. The results showed that polyethylene glycol in the molecular mass range 0.4 –20 kDa in water at physiological temperature T = 37 ° C behaves like a random coil in nearly theta solvent conditions. The obtained results serve as a reference for the description of complex mixtures with PEG used in various applications. [ABSTRACT FROM AUTHOR]

The mesoporous silica particles were prepared by the sol-gel method in one-step synthesis, in acidic conditions, from tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES), varying the mole ratio of the silica precursors. Nitric acid was used as catalyst at room temperature and hexadecyltrimethyl ammonium bromide (CTAB) as structure directing agent. Optical properties, porosity and microstructure of the materials in function of the MTES/TEOS ratio were evaluated using infrared spectroscopy, nitrogen adsorption and small angle X-ray scattering. All materials showed the ordered pore structure and the high specific surfaces, making them suitable as the drug delivery systems. Drug loading and release tests using ketoprofen were performed to assess their performance for drug delivery applications. The amount of the methylated precursor used in the synthesis had little effect on the drug loading capacity, but had a strong influence on the initial rate of the drug release. [ABSTRACT FROM AUTHOR]

Mesoporous silica particles have been prepared with functionalized precursors, used either in situ co-condensation process or as post-synthesis grafting agents, in order to deliver surface functionalisation. Aminopropyl, mercaptopropyl, vinyl and hexyl organosilanes were used as funtionalized precursors, tetraethyl orthosilicate as the base silica precursor material, hexadecyl-trimethylammonium bromide (CTAB) as directing agent and water-ethanol mixture as solvent, with ammonia catalyst. The aim was to explore the effect of various recipes on the structural properties of the composite materials. The samples' microstructures have been evaluated using nitrogen sorption and small angle neutron scattering. Ordered mesoporous structures were obtained, for almost all synthesis conditions, after the solvent-extraction of the template agent. Only in one case, for the materials functionalized by mercaptopropyl groups in co-condensation route, disordered amorphous structure was obtained. All samples functionalized by post-grafting presented well-ordered mesoporous structures. The results have potential use for easy design of sorbent materials for drug loading or pollutant adsorption applications. [ABSTRACT FROM AUTHOR]

In this study, we investigated the dispersion of carbon nanotubes and the interphases formed around them in nanocomposites with a polyamide 6 matrix (with carbon nanotube reinforcement) and hybrid composites with the same matrix, reinforced with carbon nanotubes and carbon fibers. Small-angle neutron scattering (SANS) experiments showed that carbon fibers effectively increased the dispersion of the carbon nanotubes. The average size of the carbon nanotube aggregates were significantly smaller, but the reinforcement–matrix interface area was larger in the hybrid composites than in the nanocomposites. Nanotube dispersion had a significant effect on the crystalline structure; the X-ray diffraction patterns showed that in the hybrid composites, the crystallites grew epitaxially on the surface of the well-dispersed carbon nanotubes, which resulted in decreased average crystallite size. In the hybrid composites, the smaller crystallites inferred a larger rigid amorphous fraction in the matrix. The larger interphase fraction in the hybrid composites also led to better mechanical performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Various uses of ferrofluids for technical applications continuously raise interest in the improvement and optimization of the preparation methods. This paper deals with the preparation of finely granulated magnetite particles coated with oleic acid in hydrocarbon suspensions following either chemical co-precipitation from iron salt precursors or wet milling of micron size magnetite powder with the goal to compare the benefits and disadvantages of each method. Microstructural measurements showed that both methods gave similarsized magnetite particles of 10-15 nm. The wet-milled magnetite suspension had a higher saturation magnetization than that obtained in the relatively rapid co-precipitation synthesis. The different efficacies of ferrophase incorporation into kerosene could be related to the different mechanisms of oleic acid bonding to the surface of the nanoparticles. Comparative data showed that wet milling represents a viable alternative to the traditional co-precipitation method since despite of longer processing time, the impact of chemicals on the environment and remnant water in the final product could be avoided. [ABSTRACT FROM AUTHOR]

Zero field cooled dc-magnetization measurements of monodispersed MnZnFeO nanoparticles dispersed in kerosene exhibit two transitions at low temperatures. These transitions correspond to (i) the superparamagnetic to blocked superparamagnetic and (ii) the blocked superparamagnetic to surface spin-glass like/quantum superparamagnetic state upon lowering the temperature. The existence of a disorder surface is confirmed by recording small-angle neutron scattering data below and above the Curie temperature. Magnetic relaxation analysis shows a plateau at low temperature (below 5 K) with a slight minimum at 3 K, which is a characteristic of the surface spin-glass-like state. This is analyzed considering the energy distribution n( E)∼1/ E. The existence of surface disorder dominates at low temperature and mimics the transition from superparamagnetic to quantum superparamagnetic states. [ABSTRACT FROM AUTHOR]

Abstract: Intermolecular interactions between a single water and two N,N′-dimethylethyleneurea (DMEU) molecules have been investigated using ab initio quantum chemistry method. The local and density-fitting approximations of the standard Møller–Plesset perturbation theory (DF-LMP2) have been employed together with the aug-cc-pVTZ basis set. Several trimeric systems were built where the water molecule, through the O–H⋯N hydrogen bond interactions, played the role of the bridge between the two DMEU molecules. The results show that the presence of the water molecule does not increase the stability of the trimeric systems. In the first three configurations the water molecule intercalates between two DMEU molecules, forming stable clusters. In the next three configurations, the water molecule is attached to a plane-parallel stacked DMEU dimer through the C=O⋯H–O hydrogen bond, and these structures are more stable than the first three. Small-angle neutron scattering data show clustering of DMEU molecules in their dilute aqueous solutions, and the ab initio results suggest that DMEU molecules could form contact pairs in dilute aqueous solutions. [Copyright &y& Elsevier]

Organic-inorganic silica composites have been prepared via acid catalyzed sol-gel route using tetramethoxysilan (TMOS) and methyl-trimethoxysilane (MTMS) as silica precursors and n-butyl-3-methylpyridinium tetrafluoroborate ([bmPy][BF4]) as co-solvent and pore template, by varying the content of the ionic liquid (IL). Morphology of the xerogels prepared using the ionic liquid templating agent were investigated using scanning electron microscopy and small angle neutron scattering (SANS). Thermal analysis has been used in order to evaluate the thermal and structural stability of the materials, in both nitrogen and synthetic air atmosphere. In nitrogen atmosphere, the IL decomposition took place in one step starting above 150 °C and completed in the 150–460 °C temperature interval. In synthetic air atmosphere, the IL decomposition produced two-step mass loss, mainly in the 170–430 °C temperature interval. The decomposition mechanism of the IL inside the silica matrix was studied by mass spectrometric evolved gas analysis (MSEGA). The measurements showed that the degradation of the IL's longer side chain (butyl) starts at low temperature (above 150 °C) through a C-N bond cleavage, initiated by the nucleophilic attack of a fluorine ion. [ABSTRACT FROM AUTHOR]

Abstract: Aqueous solutions of tetramethylurea (TMU) were studied by small-angle neutron and X-ray scattering at temperatures 10, 25 and 40 C in the TMU mole fraction range of 0.0125–0.025. The scattering data indicate preferential attractive interaction between the solute molecules, which becomes stronger as the temperature increases. From SANS data, concentration fluctuations and Kirkwood–Buff integrals have been calculated. The experimental data reveal a considerable solute–solute attraction above 0.01 mole fraction of TMU. These findings indicate that in addition to the usually assumed solute caging by water molecules, solute clustering of hydrophobic nature should also be considered for this system. [Copyright &y& Elsevier]

Solutions of pyridine in heavy water were studied by small-angle neutron scattering at 25 °C in the pyridine mole fraction range of 0.02–0.25. From the experimental data Kirkwood–Buff integrals and the closeness to phase separation parameters were calculated and compared with those obtained for pyridine – light water solutions from thermodynamic data available in the literature. The detailed analysis shows that a significant clustering of similar species occurs in the solution. In spite of the strongly non-ideal behavior these solutions are still far away from macroscopic phase separation. [Copyright &y& Elsevier]

[Display omitted] The co-assembly of polyelectrolytes (PE) with proteins offers a promising approach for designing complex structures with customizable morphologies, charge distribution, and stability for targeted cargo delivery. However, the complexity of protein structure limits our ability to predict the properties of the formed nanoparticles, and our goal is to identify the key triggers of the morphological transition in protein/PE complexes and evaluate their ability to encapsulate multivalent ionic drugs. A positively charged PE can assemble with a protein at pH above isoelectric point due to the electrostatic attraction and disassemble at pH below isoelectric point due to the repulsion. The additional hydrophilic block of the polymer should stabilize the particles in solution and enable them to encapsulate a negatively charged drug in the presence of PE excess. We demonstrated that diblock copolymers, poly(ethylene oxide)- block -poly(N,N-dimethylaminoethyl methacrylate) and poly(ethylene oxide)- block -poly(N,N,N-trimethylammonioethyl methacrylate), consisting of a polycation block and a neutral hydrophilic block, reversibly co-assemble with insulin in pH range between 5 and 8. Using small-angle neutron and X-ray scattering (SANS, SAXS), we showed that insulin arrangement within formed particles is controlled by intermolecular electrostatic forces between protein molecules, and can be tuned by varying ionic strength. For the first time, we observed by fluorescence that formed protein/PE complexes with excess of positive charges exhibited potential for encapsulating and controlled release of negatively charged bivalent drugs, protoporphyrin-IX and zinc(II) protoporphyrin-IX, enabling the development of nanocarriers for combination therapies with adjustable charge, stability, internal structure, and size. [ABSTRACT FROM AUTHOR]

Abstract: Equilibrium geometries of methylene chloride dimers have been calculated using the local version of second order Møller–Plesset perturbation theory (LMP2), combined with the density fitting (DF) technique. Five distinct energy minimum bonded conformations have been resolved. The results have been compared to the intramolecular geometries and the intermolecular orientational correlations obtained previously from neutron and X-ray scattering experiments combined with molecular dynamics and reverse Monte Carlo modeling. [Copyright &y& Elsevier]

The studies were focused on the relationship between morphology features and synthesis variables, looking for their implications in the drug loading and release capacities. Increasing the amount of methylated tri-alcoxide toward the tetra-alcoxide precursor caused shrinkage of the hexagonally ordered mesoporous structure and also the reduction of the pore diameters, while the total pore volumes and surface areas remain high and suitable for drug loading. In drug release profiles: silica prepared with the largest amount of hydrophobic precursor retained about twice as much of drug, compared with the sample obtained of pure TEOS.The studies were focused on the relationship between morphology features and synthesis variables, looking for their implications in the drug loading and release capacities. Increasing the amount of methylated tri-alcoxide toward the tetra-alcoxide precursor caused shrinkage of the hexagonally ordered mesoporous structure and also the reduction of the pore diameters, while the total pore volumes and surface areas remain high and suitable for drug loading. In drug release profiles: silica prepared with the largest amount of hydrophobic precursor retained about twice as much of drug, compared with the sample obtained of pure TEOS. [ABSTRACT FROM AUTHOR]

The intermolecular interaction in difluoromethane, dichloromethane, dibromomethane, and diiodomethane dimers has been investigated using high level quantum chemical methods. The potential energy curve of intermolecular interaction along the C⋯C bond distance obtained using the coupled-cluster theory with singles, doubles, and perturbative triples excitations CCSD(T) were compared with values given by the same method, but applying the local (LCCSD(T)) and the explicitly correlated (CCSD(T)-F12) approximations. The accuracy of other theoretical methods—Hartree–Fock (HF), second order Møller–Plesset perturbation (MP2), and dispersion corrected DFT theory—were also presented. In the case of MP2 level, the canonical and the local-correlation cases combined with the density-fitting technique (DF-LMP2)theories were considered, while for the dispersion-corrected DFT, the empirically-corrected BLYP-D and the M06-2Xexchange-correlation functionals were applied. In all cases, the aug-cc-pVTZ basis set was used, and the results were corrected for the basis set superposition error (BSSE) using the counterpoise method. For each molecular system, several dimer geometries were found, and their mutual orientations were compared with the nearest neighbor orientations obtained in recent neutron scattering studies. The nature of the intermolecular interaction energy was discussed. [ABSTRACT FROM AUTHOR]

In this work, the nanostructure of oxide dispersion-strengthened steels was studied by small-angle neutron scattering (SANS), transmission electron microscopy (TEM), and atom probe tomography (APT). The steels under study have different alloying systems differing in their contents of Cr, V, Ti, Al, and Zr. The methods of local analysis of TEM and APT revealed a significant number of nanosized oxide particles and clusters. Their sizes, number densities, and compositions were determined. A calculation of hardness from SANS data collected without an external magnetic field, or under a 1.1 T field, showed good agreement with the microhardness of the materials. The importance of taking into account two types of inclusions (oxides and clusters) and both nuclear and magnetic scattering was shown by the analysis of the scattering data. [ABSTRACT FROM AUTHOR]

We report on the structural evaluation of high fat fish oil-in-water emulsions emulsified with sodium caseinate (CAS) and phosphatidylcholine (PC). The microemulsions contained 70% (w/w) fish oil with 1.05–1.4% (w/w) CAS and 0.4–1.75% (w/w) PC and were studied by the combination of light scattering together with small-angle X-ray and neutron scattering (SAXS/SANS). Aqueous CAS forms aggregates having a denser core of about 100 kDa and less dense shell about 400 kDa with the hard sphere diameter of 20.4 nm. PC appears as multilayers whose coherence length spans from 40 to 100 nm. PC monolayer separates oil and water phases. Moreover, 80% CAS particles are loosely bound to the interface but are not forming continuous coverage. The distance between aggregated CAS particles in microemulsion is increased compared to CAS aggregates in pure CAS-in-water system. PC multilayers become larger in the presence of oil-water interface compared to the pure PC mixtures. Bilayers become larger with increasing PC concentration. This study forms a structural base for the combination of CAS and PC emulsifiers forming a well-defined thin and dense PC layer together with thick but less dense CAS layer, which is assumed to explain its better oxidative stability compared to single emulsifiers. [ABSTRACT FROM AUTHOR]

Stable mineral colloids play a role in the mobilization of actinide contaminants in the environment. In this paper we present a method to isolate and identify colloids released from high surface area sorbents associated with a proposed clay mineral barrier in a nuclear waste repository. The mineral colloids, which have a strong tendency to remain dispersed in solution, were separated from Al 13 - or (Ce Al)-pillared clay sediment, adsorbed on glass together with hydrolyzed vanadium(IV) species and studied by a variety of techniques including grazing-incidence X-ray scattering (GIXS), small-angle X-ray scattering (SAXS), Fourier transform-infrared spectroscopy (FT-IR) and atomic force microscopy (AFM). We show that the clay platelets are dimensionally orientated in the continuous, transparent 100 nm thick film until the onset of vanadium oxides above 350 °C. Organic matter and the secondary mineral quartz limit the swelling capacity of the platelets, an indication that the stable colloids originate from a part of the native clay that could not be intercalated by aluminum cations. X-ray scattering from oriented clay films intercalated by aluminum- and mixed cerium/aluminum oxo-hydroxy cations are also investigated by the GIXS technique. Unlabelled Image • A continuous, vanadium hydroxide/clay-colloid thin film was self-assembled on glass. • Clay nanoplates dimensionally orient within the 100 nm thick film. • Platelet orientation is preserved until the onset of vanadium oxides above 350 °C. • The platelets are potentially useful for actinide/clay-colloid transport studies. [ABSTRACT FROM AUTHOR]

In this study, we investigated the cytotoxicity of doxorubicin (DOX)-loaded magnetic nanofluids on 4T1 mouse tumor epithelial cells and MDA-MB-468 human triple-negative breast cancer (TNBC) cells. Superparamagnetic iron oxide nanoparticles were synthesized using sonochemical coprecipitation by applying electrohydraulic discharge treatment (EHD) in an automated chemical reactor, modified with citric acid and loaded with DOX. The resulting magnetic nanofluids exhibited strong magnetic properties and maintained sedimentation stability in physiological pH conditions. The obtained samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, UV-spectrophotometry, dynamic light scattering (DLS), electrophoretic light scattering (ELS), vibrating sample magnetometry (VSM), and transmission electron microscopy (TEM). In vitro studies using the MTT method revealed a synergistic effect of the DOX-loaded citric-acid-modified magnetic nanoparticles on the inhibition of cancer cell growth and proliferation compared to treatment with pure DOX. The combination of the drug and magnetic nanosystem showed promising potential for targeted drug delivery, with the possibility of optimizing the dosage to reduce side-effects and enhance the cytotoxic effect on cancer cells. The nanoparticles' cytotoxic effects were attributed to the generation of reactive oxygen species and the enhancement of DOX-induced apoptosis. The findings suggest a novel approach for enhancing the therapeutic efficacy of anticancer drugs and reducing their associated side-effects. Overall, the results demonstrate the potential of DOX-loaded citric-acid-modified magnetic nanoparticles as a promising strategy in tumor therapy, and provide insights into their synergistic effects. [ABSTRACT FROM AUTHOR]

Sequential ultra-small-angle and small-angle and X-ray scattering (USAXS and SAXS) measurements of hierarchical microstructure of a common energetic material, the high explosive 2,4,6-Triamino-1,3,5-trinitrobenzene (TATB), were performed to follow the microstructure evolution upon applied pressure. The pellets were prepared by two different routes—die pressed from a nanoparticle form and a nano-network form of TATB powder. The derived structural parameters, such as void size, porosity, and the interface area, reflected the response of TATB under compaction. Three populations of voids were observed in the probed q range from 0.007 to 7 nm−1. The inter-granular voids with size larger than 50 nm were sensitive to low pressures and had a smooth interface with the TATB matrix. The inter-granular voids with size of ~10 nm exhibited a less volume-filling ratio at high pressures (>15 kN) as indicated by a decrease of the volume fractal exponent. The response of these structural parameters to external pressures implied that the main densification mechanisms under die compaction were the flow, fracture, and plastic deformation of the TATB granules. Compared to the nanoparticle TATB, the applied pressure strongly influenced the nano-network TATB due to its more uniform structure. The findings and research methods of this work provide insights into the structural evolution of TATB during densification. [ABSTRACT FROM AUTHOR]

The structure and interaction parameters of the water-soluble cholesterol-based surfactant, Chobimalt, are investigated by small-angle neutron and X-ray scattering techniques. The obtained data are analyzed by a model-independent approach applying the inverse Fourier transformation procedure as well as considering a model fitting procedure, using a core-shell form factor and hard-sphere structure factor. The analysis reveals the formation of the polydisperse spherical or moderately elongated ellipsoidal shapes of the Chobimalt micelles with the hard sphere interaction in the studied concentration range 0.17–6.88 mM. The aggregation numbers are estimated from the micelle geometry observed by small-angle scattering and are found to be in the range of 200–300. The low pH of the solution does not have a noticeable effect on the structure of the Chobimalt micelles. The critical micelle concentrations of the synthetic surfactant Chobimalt in water and in H2O-HCl solutions were obtained according to fluorescence measurements as ~3 μM and ~2.5 μM, respectively. In-depth knowledge of the basic structural properties of the detergent micelles is necessary for further applications in bioscience and biotechnology. [ABSTRACT FROM AUTHOR]

Chemical co-precipitation from ferrous and ferric salts at a 1:1.9 stoichiometric ratio in NH4OH base with ultrasonication (sonolysis) in a low vacuum environment has been used for obtaining colloidal suspensions of Fe3O4 nanoparticles coated with citric acid. Before coating, the nanoparticles were processed by electrohydraulic discharges with a high discharge current (several tens of amperes) in a water medium using a pulsed direct current. Magnetite nanoparticles were obtained with an average crystallite diameter D = 25–28 nm as obtained by XRD and particle sizes of 25 nm as measured by small-angle X-ray scattering. Magnetometry showed that all samples were superparamagnetic. The saturation magnetization for the citric acid covered samples after electrohydraulic processing showed higher value (58 emu/g) than for the directly coated samples (50 emu/g). Ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy showed the presence and binding of citric acid to the magnetite surface by chemisorption of carboxylate ions. Hydrodynamic sizes obtained from DLS and zeta potentials were 93 and 115 nm, −26 and −32 mV for the citric acid covered nanoparticles and 226 nm and 21 mV for the bare nanoparticles, respectively. The hydraulic discharge treatment resulted in a higher citric acid coverage and better particle dispersion. The developed method can be used in nanoparticle synthesis for biomedical applications. [ABSTRACT FROM AUTHOR]

By combining oppositely charged polydiallyldimethylammonium chloride (PDADMAC) and sodium polyacrylate (NaPA), interpolyelectrolyte complexes (IPECs) can be formed in aqueous solution. Such IPECs are studied for rather short NaPA and under variation of the Mw of PDADMAC. The focus is on elucidating the effect of having a hydrophobic modification of the NaPA, which is introduced by having 10 mol% of the monomeric units substituted by ones carrying a dodecyl alkyl chain. This modification renders the complexes more hydrophobic, which is seen in the fact that precipitation of the complexes occurs at a lower mixing ratio and the biphasic region is also wider. The structures of the soluble IPECs are studied by a combination of light and neutron scattering (SANS). It is observed that the complexes formed possess typical radii of gyration of ≈30–40 nm, which become somewhat smaller with increasing length of the PDADMAC chain. The SANS data can be described well with the Beaucage model for complexes, where locally small hydrophobic domains of cylindrical shape are formed, whose persistence length decreases with increasing content of NaPA in the complexes. In contrast no such structures are seen for NaPA without the hydrophobic modification. The cylindrical domains are then arranged within larger‐sized clusters of 30–40 nm, which become more compact with reduced length of the PDAMAC chains. The structure of the IPECs is largely determined by the presence of the hydrophobic modification of the NaPA and is further controlled by the length of the hydrophobic modification. Such IPECs of controlled structure, relatively small size, and containing hydrophobic domains are potentially interesting as delivery systems due to having domains of variable polarity. [ABSTRACT FROM AUTHOR]

Magnetic iron oxide-silica shell nanocomposites (IONP@SiO2) have been prepared in a two-step procedure. IONPs were obtained by coprecipitation of iron salts, and coated by silica in sol-gel method under sonication. Two IONP/silica ratios and two drying methods, heating in oven and supercritical CO2 drying, were used. The samples were analyzed using X-ray diffraction (XRD), infrared spectroscopy, magnetic measurements, small-angle neutron scattering (SANS), nitrogen sorption, and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX). The iron oxide silica nanocomposites obtained via supercritical drying exhibited higher values of the specific surface area and of saturation magnetization compared to the samples synthesized with the same iron oxide content but obtained after drying at 60 °C. Pd(II) adsorption experiments were performed on the materials prepared by supercritical drying. The maximum adsorption capacity 6.5 mg/g showed that the materials can be used as good and cheap adsorbent for palladium ions from aquatic environment. [ABSTRACT FROM AUTHOR]

Reliability and lifetime are the two most relevant design considerations in the production of safety critical assemblies. For example in a modern automobile dozens of electronic assemblies are integrated in which thousands of solder joints are mounting the electronic components to the printed circuit boards. There exists no standardised and universal observation method for characterising the fine microstructure of such solder joints. Previously we have developed a new method for the quantitative characterization of lead-free solder alloys and in present study the validity of the proposed method is demonstrated. Microstructure of Sn-3.5Ag lead free solder alloy was investigated by electrochemical impedance spectroscopy. Solder samples were solidified with different cooling rates in order to induce differences in the microstructure. Microstructure of the ingots was revealed by selective electrochemical etching. Electrochemical impedance spectra (EIS) were measured before and after the selective etching process. The complex impedance spectra contain information about microstructure of the solder alloys. Comparison and modelling of two EIS spectra allowed obtaining a characteristic parameter of surface structure of the etched specimens. The EIS measurements were complemented with small angle neutron scattering measurements and scanning electron microscopy, in order to correlate the EIS parameter with the magnitude of the interface of the β-Sn and Ag 3 Sn phases. [ABSTRACT FROM AUTHOR]

We report how the solution structure, β-conformation and film morphology develop in poly(9,9-dioctylfluorene) (PFO) solutions and suspensions, as well as in subsequently prepared films when the molecular weight and solvent quality are systematically varied in toluene-acetone mixtures. The polymer series with molecular weights ranging from 10 kDa to 100 kDa is prepared using the precipitation fraction. The β conformation is favored by increasing molecular weight (≥30 kDa) and decreasing solvent quality (≥45 % acetone content). The content of the β conformation in the films is significantly increased when the β conformation already exists in precursor suspensions. In contrast, when there is no β conformation in the precursor solution, no β conformation will appear in the films. The mechanisms of phenomenological transformation are discussed. This work is a step toward developing quantitative guidelines for controlling PFO solutions and their film properties. [Display omitted] • β conformation of PFO is influenced by molecular weight and mixed solvent, in both solutions and films. • The β conformation and chain structure of the film are partially related to the solution. • Aggregates in solution can form sheet-like aggregates or even network. • The β content in film is higher than that in solution due to the spin-out of liquid rich in α. [ABSTRACT FROM AUTHOR]

The influence of cholesterol and β-sitosterol on egg yolk phosphatidylcholine (EYPC) bilayers is compared. Different interactions of these sterols with EYPC bilayers were observed using X-ray diffraction. Cholesterol was miscible with EYPC in the studied concentration range (0-50 mol%), but crystallization of β-sitosterol in EYPC bilayers was observed at X ≥ 41 mol% as detected by X-ray diffraction. Moreover, the repeat distance (d) of the lamellar phase was similar upon addition of the two sterols up to mole fraction 17%, while for X ≥ 17 mol% it became higher in the presence of β-sitosterol compared to cholesterol. SANS data on suspensions of unilamellar vesicles showed that both cholesterol and β-sitosterol similarly increase the EYPC bilayer thickness. Cholesterol in amounts above 33 mol% decreased the interlamellar water layer thickness, probably due to "stiffening" of the bilayer. This effect was not manifested by β-sitosterol, in particular due to the lower solubility of β-sitosterol in EYPC bilayers. Applying the formalism of partial molecular areas, it is shown that the condensing effect of both sterols on the EYPC area at the lipid-water interface is small, if any. The parameters of ESR spectra of spin labels localized in different regions of the EYPC bilayer did not reveal any differences between the effects of cholesterol and β-sitosterol in the range of full miscibility. [ABSTRACT FROM AUTHOR]

Abstract: The intermolecular interaction of non-saturated (oleic acid) and saturated (stearic and myristic acids) mono-carboxylic acids in a non-polar organic solvent (deuterated benzene) is derived from the concentration dependence of the small-angle neutron scattering. The excluded volume repulsion dominates over the attraction (supposed due to van der Waals forces) for oleic and myristic acids. In turn, for stearic acid the attractive component is higher than the repulsive one; this results in a shift of the transition into the liquid crystalline state (because of molecule anisotropy) towards smaller concentrations and could explain early data on worse stabilization properties of stearic acid in ferrofluids compared to oleic and myristic acids. [Copyright &y& Elsevier]

Partial molar volumes V ¯ 2 values of water in the 1,2-Hexanediol/1,5-Pentanediol (1) + water (2) binary mixtures versus molar fraction x 1, at 298.15 K. [Display omitted] • Physico-chemical properties data of alkanediols (1) + water binary (2) mixtures were reported. • The densities and refractive indices data were used to calculate the derived volumetric properties. • The speeds of sound data were used to calculate the excess isentropic and excess molar isentropic compressibilities. • The excess properties were correlated with the Redlich-Kister equation and with the Prigogine-Flory-Patterson model. • The results are discussed in terms of structural effects between components. The thermophysical properties data as densities, speeds of sound, and refractive indices for aqueous binary mixtures of 1,2-hexanediol and 1,5-pentanediol, have been measured at several temperatures in the range of (298.15–318.15) K, atmospheric pressure, and in the whole domain (0 to 1) of diol molar fractions. From the obtained experimental values, the related excess and deviation quantities, namely the excess molar volumes, the partial/apparent molar volumes, the isentropic compressibilities, the excess isentropic compressibilities and the deviation in refractive indices were calculated. The excess thermodynamic properties were correlated with the Redlich-Kister polynomial equation. The experimental excess molar volumes values have been also used to test the applicability of the Prigogine-Flory-Patterson theory and the results were analyzed in terms of molecular interactions between the components of the mixture. Discussions concerning the experimental and calculated results in relation to the molecular interactions and structural effects between components of mixtures are presented. In the dilute range, at (0 to 0.3) diol mole fractions, the characteristic behavior of the excess and partial molar quantities was related to the structural changes in the mixtures as observed by neutron scattering. [ABSTRACT FROM AUTHOR]

Abstract: Structure of hydrophilic epoxy networks swollen in deuterated water has been investigated by small-angle neutron scattering (SANS). Two series of the networks were prepared by end-linking reaction of α,ω-diamino terminated poly(oxypropylene)-block-poly(oxyethylene)-block-poly(oxypropylene) (POP–POE–POP), α,ω-diamino terminated poly(oxypropylene) (POP) and diglycidyl ether of Bisphenol A propoxylate (PDGEBA). In the first series, prepared using functionalized POP–POE–POP and PDGEBA, hydrophilicity of the networks was controlled via cross-linking density of the networks, changing the initial ratio of reactives. In the second series, POP–POE–POP was gradually substituted by POP of the same molecular weight, enabling a control of hydrophilicity of the networks at essentially constant crosslinking density in this way. Microphase separated structure of the networks swollen in deuterated water with composition variations on nanometer scale was found by SANS. The scattering data were fitted to the Percus–Yevick model, approximating the swollen network by an idealized system of spheres dispersed in the matrix. Satisfactory fits in the region of the interference scattering peak were obtained giving values 30–70Å for the average radius of the spherical regions. Radius of the spheres increases with increasing hydrophobicity of the networks (growing POP content and/or network crosslinking density). [Copyright &y& Elsevier]

Superparamagnetic iron oxide nanoparticles (SPIONs) have attracted the particular interest of scientists from various disciplines since their obtaining to the present day. The physicochemical and pharmacokinetic properties of SPIONs-containing magnetic nanofluids, and their applicability in biomedicine, largely depend on the stability of the colloidal system, particle size, size distribution, net magnetic moment, phase composition, and type and properties of stabilizers. Also, in some cases, when using magnetic nanoparticles for biomedical purposes, it is necessary that the stabilizing ligands of nanoparticles should not significantly change the magnetic properties. From this point of view, the preparation of stable colloidal systems containing bare iron oxide nanoparticles (BIONs) in water at physiological pH attracts particular attention and becomes increasingly popular in scientific circles. This study is focused on the development of the synthesis of aqueous suspensions of SPIONs stabilized with various organic molecules (oleic acid [OA] and poly(ethylene glycol) monooleate - with molecular weights 460 and 860) using a modified controlled chemical coprecipitation reaction, as well as stable nanofluids containing BIONs in an aqueous medium at neutral pH (near-physiological). The obtained samples were characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy, small-angle x-ray scattering (SAXS), dynamic light scattering (DLS), electrophoretic light scattering (ELS), and Vibrating Sample Magnetometry. [ABSTRACT FROM AUTHOR]

The sonochemical coprecipitation reaction with moderate ultrasound irradiation in a low vacuum environment was used to obtain aqueous colloidal suspensions of iron oxide nanoparticles (IONPs). The synthesized magnetite nanoparticles were conjugated directly by folic acid using electrohydraulic discharges as a processing technique before modification of the surface of the nanoparticles. Electrohydraulic discharges were applied in two operational modes with high and low power pulsed direct currents between the electrodes. The physical and chemical properties of the obtained samples were studied using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). The investigation proved an inverse cubic spinel structure of magnetite with folic acid attachment to the magnetite surface (mean crystallite diameter in the samples, D, ranges 25-31 nm by XRD and SAXS). It was found that the processing with electrohydraulic discharges increased the colloidal stability of the folic acid-magnetite nanoparticle dispersions. [ABSTRACT FROM AUTHOR]

We report results of measurements of first-order reversal curves (FORCs) for neutron irradiated reactor pressure vessel steels to seek their possible application to a nondestructive evaluation of the irradiation hardening. We find a peak position of the FORC distribution, which is the second derivative of measured FORCs, shifts towards zero field after neutron irradiation, associated with the narrowing of the peak width. The observations indicate the progress of the magnetic softening and magnetic homogeneity under neutron irradiation. The present investigations demonstrate that FORCs can offer additional information on microstructural changes due to neutron irradiation, which can not be obtained by a conventional hysteresis method. [ABSTRACT FROM AUTHOR]

• Composites were prepared based on 316 L with 0.33–1 wt.% Si 3 N 4 and Y 2 O 3 by spark plasma sintering. • The hardness of CDS and ODS were significantly higher than for reference. • The submicron sized particles were detected by SANS in CDS with lower concentration. • Samples exhibit ferromagnetic property, a large ferromagnetic component evolved with thermal aging. • ODS and CDS samples showed saturation magnetization dependent on ageing temperature and time. The effect of the ultrafine grained silicon nitride and yttria addition to the morphological, structural, mechanical and magnetic properties of the ceramic dispersion strengthened 316 L stainless steels prepared by powder technology has been studied. Four composites have been prepared: 316 L/0.33 wt.% Si 3 N 4 , 316 L/1 wt.% Si 3 N 4 (CDS) and 316 L/0.33 wt.% Y 2 O 3 , 316 L/1 wt.% Y 2 O 3 (ODS). Spark plasma sintering (SPS) was used for fast compaction of milled composite powders. The hardness values have been found to be significantly higher in the cases of CDS and ODS samples in comparison to reference sample, whereas the ODS composites had lower smaller hardness than the CDS composites regardless the content of additives. The magnetic characterization of samples demonstrated that the samples exhibit ferromagnetic property already before ageing and a larger ferromagnetic component was observed as a result of thermal aging. It was proven that in the case of ODS and CDS samples with a low amount of Y 2 O 3 or Si 3 N 4 the saturation magnetization was slightly dependent on ageing time, however, it exhibited a noticeable change with ageing both at 600 and 800 °C for samples containing higher amount of additives. [ABSTRACT FROM AUTHOR]

Simulation (molecular dynamics and Car-Parrinello [Phys. Rev. Lett. 55, 2471 (1985)]) and diffraction (x-ray and neutron) studies on nitromethane are compared aiming at the determination of the liquid structure. Beyond that, the capabilities of the methods to describe liquid structure are discussed. For the studied liquid, the diffraction methods are performing very well in the determination of intramolecular structure, but they do not give detailed structural information on the intermolecular structure. The good agreement between the diffraction experiments and the results of molecular dynamics simulations justifies the use of simulations for the more detailed description of the liquid structure using partial radial distribution functions and orientational correlation functions. Liquid nitromethane is described as a molecular liquid without strong intermolecular interactions such as hydrogen bonding, but with detectable orientational correlations resulting in preferential antiparallel order of the neighboring molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simplified preparation of thiol functionalized short range ordered mesoporous silicas. • Selective sorption of aqueous Ag(I) with a capacity of 238 mg g−1 at pH = 5.0. • Sorption equilibrium establishes extremely fast, in 15 min contact time. • Strong and selective binding of Ag(I) due to the formation of layered thiolate coordination compounds on the surface. • Quantitative recovery of Ag(I) and sorbent regeneration with 10 mM Na 2 S 2 O 3 solution. A simplified sol–gel method was developed for the preparation of thiol functionalized porous silica particles using (3-mercaptopropyl)-trimethoxy-silane (MPTMS) for co-gelation in the presence of micellar templates. The resulting short range ordered porous silica microparticles are exceptionally effective sorbents of aqueous Ag(I). The binding of aqueous Ag(I) is almost stoichiometric in the broad pH range between 4.0 and 9.0 even at low Ag(I) concentrations until reaching the limiting 238 mg g−1 sorption capacity. The sorbent displays high selectivity towards Ag(I), which was tested in the simultaneous presence of several different metal compounds. The practically complete recovery of Ag(I) and the regeneration of the sorbent was achieved by washing with a 10 mM Na 2 S 2 O 3 solution. X-ray photoelectron spectroscopy (XPS) revealed that silver is not reduced on the surface of the sorbent. The reason for the strong and selective binding of Ag(I) is the formation of layered thiolate coordination compounds on the functionalized silica surface that display characteristically high stability even in the presence of other competing metal ions. [ABSTRACT FROM AUTHOR]

• Non-Fickian water absorption behavior is exhibited in high temperature. • Water interacts first with free carbonyl group and then with hydrogen-bonded carbonyl group. • Water absorption results in the disintegration of the loose hard domains. • The stress relaxation is remarkable accelerated with water absorption. The influence of water absorption on molecular dynamics, microstructures and relaxation behaviors of polyurethane (PU) elastomers with polyether (poly(tetramethylene glycol), PTMG) soft segments has been studied. Kinetics of water absorption of PU elastomer can be well fitted by Fick's model. However, non-Fickian absorption behavior was observed in the late stage at 60 °C, which was presumed to be related to the plasticization of some hard domains. Broadband dielectric relaxation spectroscopy was used to investigate the molecular dynamics of PU elastomers. The analysis of α -relaxation and Maxwell-Wagner-Sillars interfacial polarization indicated that the water absorption has a great influence on the molecular mobility of soft segment and the interface regions between soft domains and hard domains. Microphase separation structures of PU elastomers consisted of loose, partially regular and compact hard domains. Water molecules could interact with loose hard domains and lead to the plasticization. The results of stress relaxation behavior indicated that water absorption leaded to remarkable increase in the stress relaxation ratio. The deterioration of relaxation properties caused by water absorption was not only related to the soft segments, but also caused by the plasticization of the interface regions and the hard domains. [ABSTRACT FROM AUTHOR]

A series of calibration measurements have been performed on Suanni – the first small‐angle neutron scattering spectrometer entering into routine user operation in China – aiming to characterize instrument performance and to provide a reference for user experiments. Various calibration standards were used to verify the precise association of the scattering intensity I with the scattering vector magnitude q at short and medium sample–detector distances. The measurements recorded for silver behenate powder revealed a slight shift of the neutron wavelength (λ) at the sample position as compared to the nominal λ calculated by the selector constant. The deviation was more significant with λ > 0.8 nm owing to the shape of the incoming neutron spectrum incident on the selector. The measured dead time for the entire detection system is 2.7 µs, as determined by measurements with varying fluxes. A protonated/deuterated polystyrene blend was employed as the primary standard to calibrate the secondary standard H2O. The instrument covers an effective q range between 0.013 and 5 nm−1, as demonstrated by scattering curves obtained from a monodisperse poly(methyl methacrylate) nanoparticle suspension and a glassy carbon plate. The wavelength, the scattering vector magnitude and the absolute intensity for the Suanni small‐angle neutron scattering spectrometer have been calibrated by using standard samples, providing an informative reference for users and diagnostic tools for instrument scientists. [ABSTRACT FROM AUTHOR]

Superparamagnetic γ -Fe 2 O 3 nanoparticles (5 nm diameter) were synthesized in water. The bare particles exhibit good colloidal stability at ∼pH 2 because of the strong electrostatic repulsion with a surface charge of +25 mV. The polyacrylic acid (PAA)-coated particles exhibit remarkable colloidal stability at ∼pH 7 with abundant free carboxyl groups as reactive sites for subsequent functionalization. In this work, we used zeta potential analysis, transmission electron microscopy, small angle X-ray scattering, and Inductively coupled plasma mass spectrometry to investigate the adsorption behavior of U (VI) on bare and coated colloidal superparamagnetic nanoparticles at pH 2 and pH 7. At pH 2, uranyl ion (UO 2 2+ ) absorbed on the surface of the bare particles with decreasing particle surface charge. This induced particle agglomeration. At pH 7, uranyl ion (UO 2 2+ ) hydrolyzed and formed plate-like particles of uranium hydroxide that were ∼50 nm in diameter. The PAA-coated iron oxide nanoparticles absorbed on the surface of these U (VI) hydroxide plates to form large aggregates that precipitate to the bottom of the dispersion. At both pH 2 and pH 7, the resulting U (VI)/nanoparticle complex can be easily collected and extracted from the aqueous environment via an external magnetic field. The results show that both bare and polymer-coated superparamagnetic γ -Fe 2 O 3 nanoparticles are potential absorbents for removing U (VI) from water. [ABSTRACT FROM AUTHOR]

Small-angle scattering was employed to characterize the gradual phase mixing and separation of Estane 5703p, a type of polyester polyurethane, as a function of temperature (20–110 °C) and time (minutes to 80 days). The polymer structure was modelled by polydisperse hard spheres, and microstructure evolution of the material was inferred from the development of the fitting parameters. At temperatures higher than 40 °C, the scattering data indicated the mixing of hard domains (MDI-BDO) with soft matrix (PBA). The hard domain distance showed a sharp increase at 50–60 °C. Between 60 and 90 °C, a newly-observed ordering signalled the formation of a distinct mesophase with a repeat distance of 5.15 nm. Upon heating, the morphology evolution in Estane follows: domain intermixing – mesophase formation – final melting. After cooling, the domain structure partly recovered, but did not reach the original state during storage at room temperature for 80 days. [ABSTRACT FROM AUTHOR]

The ability of bentonite and montmorillonite pillared by Al-oxide and mixed (Ln-Al)-oxides (Ln = La, Ce) to remove 239 plutonium solution species from water is comparatively investigated at pH 7 and pH 4. Small-angle scattering and neutron contrast variation with H 2 O/D 2 O mixtures is used to verify the ingress of water in the calcined products after hydrophilicity was introduced by an NH 3 -H 2 O vapor treatment. The size and shape of the (La/Ce)-Al oxo-hydroxy pillaring cations (2 nm spheres) is determined by small-angle x-ray scattering from the pillaring solutions. Not all of the oxide pillars improved Pu uptake compared with sodium montmorillonite. At neutral and acidic pH only (Ce-Al)-oxide pillared clays showed the ability to remove Pu over the concentration range studied (1.35 × 10 −8 –8 × 10 −8  mol dm −3 ) with distribution coefficient ( K D ) values >10 4 . XPS analysis of the (Ce-Al)-oxide pillared clays indicates the presence of Ce 4+ as cerium dioxide. The progressive improvement in sorption performance in the order of pillar type Al 2 O 3  < La 2 O 3 -Al 2 O 3  << CeO 2 -Al 2 O 3 reflects the increasing access of Pu solution species to the clay mineral layers by changes to the basal spacing and specific surface area, and also to the higher stability of the (Ce-Al)-oxide pillars. [ABSTRACT FROM AUTHOR]

Core-shell polymer coated superparamagnetic nanoparticles are critical tools in bio-nanotechnology, in which the soft and thin polymeric coatings play a key role in their stabilization, surface functionality and biocompatibility. Standard characterization tools, such as Transmission Electron Microscopy are indispensable for the morphological characterization of the metal-containing core but they cannot clearly discriminate between core and shell components. Dynamic Light Scattering can only overestimate the shell thickness by measuring the particle hydrodynamic diameter. Here, we describe Small-Angle X-ray Scattering and Small-Angle Neutron Scattering as tools to study poly (acrylic) acid coated gamma iron oxide superparamagnetic nanoparticles dispersed in aqueous medium. Our results show that Small-Angle Scattering techniques offers in situ and sensitive measurements of the “stealth” polymer coatings which cannot be accurately detected by other techniques. The Small Angle Scattering approach presented in this work is applicable for analysis of core-shell organic/inorganic hybrid nanoparticles systems for a broad range of applications. [ABSTRACT FROM AUTHOR]

Mesoporous silica particles have been synthesized by sol–gel method from tetraethoxysilane (tetraethylorthosilicate, TEOS) and methyltriethoxysilane (MTES), in ethanol and water mixture, at different ratios of the of the silica precursors. Ammonia was used as catalyst at room temperature and hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide, CTAB) as the structure directing agent. Nitrogen sorption, X-ray diffraction and small-angle neutron scattering gave information on the evolution of the gel structure and pore morphologies in the function of MTES/TEOS molar ratio. Thermogravimetric and differential thermal analysis showed that with addition of MTES the exothermic peak indicating the oxidation of the low molecular weight organic fragments shift to higher temperature. A room-temperature, one-pot synthesis of MCM-41 type materials is presented, in which the variation of the MTES concentration allows to change the hydrophobicity, preserving the specific properties materials, like the ordered pore structure, large specific surface area and high porosity. Specifically, the obtained materials had cylindrical pores, specific surface areas up to 1101 m 2 /g and total pore volumes up to 0.473 cm 3 /g. The obtained mesoporous materials are susceptible for further functionalization to improve their selective uptake of guest species in drug delivery applications. [ABSTRACT FROM AUTHOR]

The aggregation of a water soluble, dicationic perylene bisimide derivative was studied by means of absorption and emission spectroscopies, X-ray and neutron scattering techniques as well as electron microscopy. The results provide evidence for the existence of higher order molecular aggregates in solution, potentially utilizable in device fabrication as super molecular building blocks. [ABSTRACT FROM AUTHOR]

[Display omitted] • ex-situ and in-situ observations from the microscopic to the nanoscopic level. • SPEM and XPS provide insight into the agglomeration of chemical elements during DCT. • Mo plays a crucial role in DCT through its modification of chemical bonding states. • APT shows preferential formation of Mo-rich M 7 C 3 carbides after DCT. • SANS and SPEM confirm increased formation of M 23 C 6 carbides. The study investigates the effect of deep cryogenic treatment (DCT) on a high-alloyed ferrous alloy (HAFA) and its effectiveness on carbide evolution and chemical shifts of alloying elements. With ex-situ and in-situ observations ranging from the microscopic to the nanoscopic level, we uncover the atomistic mechanism by which DCT affects carbide precipitation, resulting in a 50% increase in carbide volume fraction. Synchrotron-based scanning photoelectron microscopy provides insight into the agglomeration of carbon during exposure to DCT. We find that Mo plays a crucial role in DCT through its modification of chemical bonding states, which is postulated to originate from the loosely-formed primordial Mo 2 C carbides formed during exposure to cryogenic temperatures. These in turn provide energetically favorable nucleation zones that accelerate the formation of M 7 C 3 carbides, which serve as intermediate states for the formation of M 23 C 6 carbides, which most strongly impact the mechanical properties. These results are supported by atom probe tomography, showing the preferential formation of Mo-rich M 7 C 3 carbides in DCT samples, resulting from greater solute mobility. This work clarifies the fundamental mechanisms on how DCT affects HAFA, solving a long-elusive problem. [ABSTRACT FROM AUTHOR]

In this research, a group of segmented polyurethane (PU) copolymers with different hard segment (HS) contents were successfully synthesized. The microstructure of the PU copolymers was characterized via Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and small-angle neutron scattering (SANS). Then, the PU copolymers were selected as polymer binder for coating an insensitive high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) to prepare polymer bonded explosives (PBXs). When the HS concentration of PU copolymers increased from 14 to 34 wt %, a 14.6 times increase in the creep rupture time of PBXs under 60 °C/3 MPa and a 52.3% decrease in the steady-state creep strain rate under 60 °C/1 MPa were observed. The experimental results indicated that a wide variety of structure and properties of PU copolymer could be customizable through the adjustment of the HS contents, and consequently, provided an efficient route to tune the creep performance of the PBXs over a wide range. [ABSTRACT FROM AUTHOR]

We have investigated effects of long-term thermal aging at 550°C up to 10000 h on major-loop coercivity, hysteresis scaling of minor loops, and first-order reversal curves (FORCs) for low-alloy pressure vessel steels with low and high Ni contents. While major-loop coercivity and minor-loop coefficient of the scaling exhibit a gradual decrease with aging for high-Ni steel, those for low-Ni one are very weakly dependent on aging time. On the other hand, we found that FORC distribution becomes steep along both axes of interaction and switching fields and the peak shifts toward a lower switching field for both steels. Considering that there is no significant development of nanoscale precipitates during the aging as revealed with small-angle neutron scattering experiments, a relaxation of lattice strain in a matrix, possibly associated with diffusion of Ni atoms, may dominate magnetic properties at 550°C. [ABSTRACT FROM AUTHOR]

Piperidine and N-methylpiperidine hydrates aggregate in liquid aqueous solutions due to hydrogen bonds between hydration water molecules. No such effects occur in the mixtures of the amines with methanol, that supports the idea of active role of water solvent in the aggregation. However, the question of contributions in thermodynamic functions due to specific interactions, van der Waals forces, and the size and shape of the molecules remains open. In the present study, limiting partial molar enthalpies of solution of pyrrolidine, N-methylpyrrolidine, piperidine, and N-methylpiperidine in water and methanol and vice versa were measured and compared with those assessed from theoretically calculated molecular interaction energies using a simple "chemical reaction" model. Nearly quantitative agreement of the enthalpies was achieved for the systems studied, except the amines in water. The latter required an empirical hydrophobic hydration term to be considered. The hydrogen bonds formation and breaking which accompany the mixtures formation leads to considerable excess volumes, while the size of the solute molecules is manifested rather in the compressibility of aqueous solutions. SANS evidenced that aqueous solutions are microheterogeneous on the nanometer-order length scale. The propensity to promote phase separation increases in the order: N-methylpiperidine < N-methylpyrrolidine < piperidine < pyrrolidine. [ABSTRACT FROM AUTHOR]

The variation of synthesis temperature made it possible to produce artificial ferritins possessing different structural and magnetic properties, size distribution, and colloidal stability. The effect of synthesis temperature on the core structure and stability of protein shell was investigated using small-angle neutron scattering, small-angle X-ray scattering, SQUID magnetometry, dynamic light scattering, and zeta potential measurements. The optimal temperature was established for the synthesis of artificial ferritin suitable for biomedical imaging applications at ∼60 °C, which is close to the protein denaturation temperature. [ABSTRACT FROM AUTHOR]

Synthesis, aggregation properties in aqueous solution and antimicrobial activity of novel urea-based cationic gemini surfactants N , N ′-bis{2-[(undecylcarbamoyl)amino]ethyl}- N , N , N′ , N ′-tetramethylalkane-α,ω-diammoniumdibromides of variable spacer length are presented as a function of surfactant molecular structure. Utilizing the experimental methods of tensiometry, dynamic light scattering, time-resolved fluorescence quenching, neutron scattering, and zeta potential, the obtained data indicate a stronger aggregation tendency of urea-based surfactants with a short spacer composed of 2 CH 2 groups which was confirmed by all applied experimental methods. As results from the comparison with the gemini surfactants without urea groups in the alkyl tails and polymethylene spacer, the presence of urea groups enhances the aggregation properties of gemini molecules through additional hydrogen bonding interactions. A simple molecular model of the hydrogen bonding interaction between neighbouring urea-based gemini molecules is provided. For longer spacers of 4–10 CH 2 groups, the existence of monodisperse spherical micelles has been confirmed. The dependence of antimicrobial activity vs. spacer length shows nonlinear parabolic behaviour with the maximum antimicrobial activity found at the spacer length of 6 CH 2 groups for bacteria and 8 CH 2 groups for fungi. This is related to a different composition of cell membrane of the used microorganisms. [ABSTRACT FROM AUTHOR]

The microstructure of compression molded Estane 5703 films exposed to 11%, 45%, and 80% relative humidity and 70 °C for 1 and 2 months has been studied by small-angle neutron scattering (SANS), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Scattering data indicated increase of the interdomain distance and domain size with a higher humidity and longer aging time. GPC data showed a progressive shortening of polyurethane chains with increasing humidity and aging time. The shortening of the polyurethane chains caused a drop of the glass transition temperature of soft segments, and promoted crystallization of the soft segments during long-time storage of the aged samples at room temperature. FTIR showed a substantial increase in the number of inter-urethane H-bonds in the aged samples. This correlates with the increase of the hard domain size and the degree of phase separation as measured by SANS. The data collected reveals that the reduced steric hindrance caused by hydrolysis of ester links in polybutylene adipate residues promotes the organization of hard segments into domains, leading to the increase of domain size and distance, as well as phase segregation in aged Estane. These findings provide insight into the effects of humidity and thermal aging on the microstructure of aged polyester urethane from molecular to nanoscale level. [ABSTRACT FROM AUTHOR]