Wide-angle X-ray Diffraction Methods Research Articles

Investigation of Phase & Strain Distributions Inside of Solid Oxide Fuel Cells

A microfocused, high energy wide angle X-ray diffraction method with micron-level spatial resolution was developed to investigate phase and strain distributions of individual components inside of planar solid oxide fuel cells (SOFCs). Examples were given for the study of a commercial SOFC sample deactivated after direct contact with the high temperature stainless steel current collector under typical operating conditions.

Tetraphenylsilane-containing polyarylates with well-defined functional groups via postpolymerization modification

New tetraphenylsilane-containing polyarylate with two pendant benzyl ester groups was synthesized successfully by direct polycondensation from a new silicon-containing aromatic diacid monomer bis[p-(benzyloxycarbonyl)phenyl]-bis(p-carboxyphenyl)silane (BBCS) with p-dihydroxybenzene in pyridine, using dimethylformamide as the activator and p-tosyl chloride as the condensing agent. Then, the benzyl ester groups were smoothly converted to carboxyl groups by catalytic hydrogenation, obtaining the polyarylate with two carboxyl groups attached on the phenylenes of tetraphenylsilane moiety. The new monomer and polyarylates were characterized by 1H NMR, FTIR, wide angle X-ray diffraction and gel permeation chromatography methods. The carboxyl-containing polyarylate exhibited good solubility in most polar aprotic solvents and had the 5% weight loss over 400°C. The presence of well-defined carboxyl groups and rigid tetrahedral structure of tetraphenylsilane in the polyarylate provides the feasible routes to the preparation of either hypercrosslinked covalent organic framework materials or optoelectronic materials through the reaction with chromophoric compounds.

Color-Tuned Highly Fluorescent Organic Nanowires/Nanofabrics: Easy Massive Fabrication and Molecular Structural Origin

The development of one-dimensional fluorescent nanowires (1D-NWs) and their higher-dimensional architectures such as nanowebs and nanofabrics (2D-NFs) could open a new area in nanomaterials science and nanotechnology. In particular, fluorescent pi-electronic 1D-NWs are considered promising materials for realizing innovative nanodevices together with semiconductors and metallic NWs. We earlier reported that 1-cyano-trans-1,2-bis-(3',5'-bis-trifluoromethyl-biphenyl)ethylene (CN-TFMBE), a simple but very peculiar derivative of oligo(p-phenylene vinylene)s (OPV) composed of a cyano-stilbene backbone, self-assembles easily into 1D-NWs with highly enhanced fluorescence emission in the solid state. We report herein surprising new outcomes obtained from a more detailed exploration of the self-association behavior of CN-TFMBE and its analogues. We found that CN-TFMBE self-assembled into highly fluorescent 1D-NWs and 2-D NFs very easily and massively, irrespective of whether drop casting, spin coating, or vacuum deposition was used for processing. However, we additionally found that, if the backbone cyano group or trifluoromethyl substituents were removed from CN-TFMBE, the resulting molecule did not form 1D-NWs under any conditions. Through structural analyses using mid- and wide-angle X-ray diffraction methods and multiscale computer simulation techniques, we formulated molecular structural guidelines for programming pi-electron molecules into highly fluorescent 1D-NWs and 2-D NFs. Interestingly, we demonstrated that R,G,B,Y-color tuned 1D-NWs and NFs could be easily and massively fabricated based on our guidelines. This class of highly fluorescent color-tuned organic pi-electronic nanomaterial is expected to open a new phase in applications such as nanoscale optoelectronics, sensing, and biological devices.

Challenges in Highly-reliable Crystal Structure Analysis of Synthetic Polymers based on the Organized Combination of Wide-Angle X-ray Diffraction and Wide-Angle Neutron Diffraction Methods.

Challenges in Highly-reliable Crystal Structure Analysis of Synthetic Polymers based on the Organized Combination of Wide-Angle X-ray Diffraction and Wide-Angle Neutron Diffraction Methods.

New heat stable and processable poly(amide–ether–imide)s derived from 5-(4-trimellitimidophenoxy)-1-trimellitimido naphthalene and various diamines

New aromatic diimide-dicarboxylic acid having flexible ether linkage, 5-(4-trimellitimidophenoxy)-1-trimellitimido naphthalene, was synthesized by the reaction of trimellitic anhydride with 5-(4-aminophenoxy)-1-naphthylamine. Then, a series of novel aromatic poly(amide–ether–imide)s were prepared by the phosphorylation polycondensation of the synthesized monomer with various aromatic diamines. A model compound was synthesized by the reaction of the monomer with aniline. The resulting polymers with inherent viscosities of 0.43–0.70 dl/g were obtained in high yield. All new compounds including the naphthalene-based monomer, model compound, and the resulted polymers were characterized by FT-IR and NMR spectroscopic methods. The ultraviolet λ max values of the poly(amide–ether–imide)s were also determined. The resulted polymers exhibited a good solubility in a variety of high polar solvents such as N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), and pyridine. For some of the polymers obtained the crystallinity behavior was estimated by means of wide-angle X-ray diffraction (WXRD) method, and the resulted polymers exhibited nearly an amorphous nature. Thermal stability of the obtained polymers was determined by thermogravimetric analysis (TGA/DTG), and the 10% weight loss temperatures of the one-step degraded poly(amide–ether–imide)s were found to be in the range between 528 and 551 °C in nitrogen. From differential scanning calorimetric (DSC) analyses, the polymers showed T gs between 276 and 307 °C. Cyclic voltammetry (CV) measurements of a typical polymer showed that they are also electrochemically stable.

New organosoluble and thermally stable poly(urea-imide)s prepared from one-pot polyaddition reactions

A new class of aromatic poly(urea-imide)s having biphenylene pendant group was prepared by the diphenyl azidophosphate (DPAP) activated one-pot polyaddition reaction of a preformed imide ring-containing dicarboxylic acid, 4-p-biphenyl-2,6-bis(4-trimellitimidophenyl)pyridine (1) with various aromatic diamines. A model compound was also synthesized by the reaction of diimide-dicarboxylic acid 1 with two mole equivalents of aniline. In this direct method the polymers were prepared by polyaddition reactions of the in situ-formed diisocyanate with the aromatic diamines. The inherent viscosities of the polymers were measured in the range of 0.11–0.15 dL g−1. The ultraviolet λmax values of the poly(urea-imide)s were also determined. Furthermore, crystallinity of the resultant polymers was evaluated by wide-angle X-ray diffraction method, and they exhibited nearly a noncrystalline nature. All of the resulting polymers exhibited excellent solubility in common polar solvents. The glass transition temperatures of the polymers determined by DSC thermograms were in the range 241–272°C. The temperatures at 10% weight loss from their TGA curves were found to be in the range 406–437°C in nitrogen. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Surface Chain Orientation during Crystallization Induction Period of Poly(pentamethylene 2,6-naphthalate) Studied with Polarized FTIR-ATR

Thermoinduced surface orientation behaviors were studied in situ by Fourier transform infrared spectroscopic (FTIR) measurements along with attenuated total reflection (ATR) and transmission methods during the cold crystallization of melt-quenched amorphous poly(pentamethylene 2,6-naphthalate) (PPN) film. The chain in the crystalline phase formed during the cold crystallization process was found to orient parallel with the film surface with a naphthalene ring perpendicular to the film plane. By observing the isothermal crystallization process via polarizing optical microscopy and wide-angle X-ray diffraction methods, it was revealed that PPN shows very slow crystallization kinetics, even when crystallized at the temperature associated with the fastest crystallization rate. Furthermore, the crystallization induction period was longer than 150 min, during which time a significant amount of crystalline phase was not to be formed. The chain orientation at the surface during the crystallization induction period was again measured via polarized FTIR-ATR spectroscopy. It was found that the preferential surface orientation occurs during the early stage of the induction period, and no further orientation was observed during the subsequent crystallization process. Rapid local ordering that occurred during the crystallization induction period, especially at the surface, appears to be followed by gradual packing of the locally ordered chain to form the crystalline phase.

Nanoindentation behaviour of layered silicate reinforced unsaturated polyester nanocomposites

The effect of various loading levels of nanoclay reinforcement on the nanomechanical properties of layered silicate nanoclay reinforced unsaturated polyester (UPE) nanocomposites were investigated by a nano-indentation test method. The clay was dispersed into a UPE matrix via blending using a mechanical stirrer. Structural studies were carried out using a wide angle X-ray diffraction (WAXD) method and correlated with the nanoindentation results. This shows that nanoindentation behaviour is strongly influenced by clay reinforcement and the degree of clay dispersion in the polymer matrix. The experimental results show that there is a strong correlation between nanomechanical properties and inter layer d-spacing of clay particles in the nanocomposite system. Incorporation of 1%, 3% and 5% by weight nanoclay into the polyester resin results in an improvement in hardness of 29%, 24% and 14%, respectively. The elastic modulus increased from 5393 MPa for unreinforced polyester to 6646 MPa (23% increase) with the introduction of 5% by weight nanoclay.

Sequence distribution and crystal structure of poly(ethylene/trimethylene terephthalate) copolyesters

The sequence distribution and the crystal structure of copolyesters synthesized from ethylene glycol, 1,3-propanediol, and dimethyl terephthalate with different molar volume ratios were investigated in this study. The triad sequence probabilities of ethylene/trimethylene terephthalate were characterized from the aromatic quaternary carbons by 13C NMR. The composition of the copolyesters was determined from the aromatic quaternary carbons by 13C NMR, and the methylene protons by 1H NMR. Results show that 1,3-propanediol reacted faster with terephthalic acid in copolyester polymerization than ethylene glycol. The difference in monomer reactivity is significant in the polymerization. Although the constitutional units revealed a random distribution in the molecular chain by 13C NMR, crystallites formed across the full range of ethylene glycol/1,3-propanediol composition by use of differential scanning calorimetry, a hot stage polarizing microscope, and a wide angle X-ray diffraction method. The WAXD deconvolution results show that the major constitutional repeating unit in the molecular chain dominates the crystal structure as a host crystal. The crystal structure was examined by a scanning electron microscope after a solvent etching. Photomicrographs show that the random distribution of the third constitutional unit in the molecular chain of copolyester significantly disturbs the host crystal formation and lamellar orientation.

Study on Smectic Liquid Crystal Glass and Isotropic Liquid Glass Formed by Thermotropic Main-Chain Liquid Crystal Polyester

Two distinct glassy states formed by a thermotropic main-chain BB-3(1-Me) polyester were characterized by the wide-angle X-ray diffraction and DSC methods. In the BB-3(1-Me), a smectic CA liquid crystal (LC) was formed from an isotropic liquid on gradual cooling at rates smaller than 1 °C min-1 and solidified without crystallization, resulting in the smectic LC glass. On the other hand, the isotropic liquid solidified without the liquid crystallization on rapid cooling at rates larger than 50 °C min-1, resulting in the isotropic liquid glass. On heating, the smectic LC glass showed a glass transition (TgLC) of 81 °C, while the isotropic liquid glass showed a glass transition (Tgiso) of 93 °C and transformed to the smectic LC at 110 °C. The corresponding heat capacity increases were 50.1 and 78.5 J mol-1 K-1 for the smectic LC glass and the isotropic liquid glass, respectively. The enthalpy−temperature relationship in all the states was estimated by integration of the heat capacity measured by the temperat...

Latex interpenetrating networks based on polyurethane, polyacrylate and epoxy resin

Firstly the polyurethane (PU)/polyacrylate (PA) latex interpenetrating networks (LIPNs) were synthesized and the miscibility of PU/PA LIPN was investigated with differential scanning calorimetry (DSC). The effects of different PU/PA composition, the blending pattern and NCO/OH molar ratios on LIPNs performance have also been characterized using DSC, wide-angle X-ray diffraction (WAXD) methods. The particle size and its distribution were determined by dynamic light scattering (DLS) instrument. It has been found that the miscibility of PU/PA LIPNs is superior to the corresponding physical polymer blending systems due to a considerable extent of interpenetration and entanglement between PU and PA latex. PU/PA LIPNs can improve water resistance of PU dispersion emulsion; however, they are inferior to corresponding solvent-based counterparts. In order to solve the problem, a new kind of novel ternary LIPN of PU/PA/epoxy (EP) resin was synthesized. The water resistance of films was improved considerably. The effects of EP resin content on water resistance and mechanical properties of films were also explored in this paper.

Stable cubic phases in codispersions of glucocerebroside and palmitoyloleoylphosphatidylethanolamine

The effect of glucocerebroside (GlcCer) on the structure and thermotropic phase behavior of aqueous dispersions of palmitoyloleoylphosphatidylethanolamine (POPE) has been examined using simultaneous small-angle and wide-angle X-ray diffraction methods. Binary mixtures of GlcCer:POPE in molar ratios of 2:100, 5:100, 10:100, 20:100, 30:100, and 40:100 were examined in the temperature range 20–90 °C. Cubic phase has been observed in binary mixtures comprised of molar ratios greater than 5:100 in the temperature range of 60–90 °C upon heating at a rate of 2 °C/min. The cubic phase is relatively stable and coexists with inverted hexagonal or lamellar phases. It persists in the codispersions throughout subsequent cooling scans to 30 °C. The space group of the cubic phase is determined to be Pn3 m or Pn3. The lattice constant of the Pn3 m cubic phase was found to be almost constant when it coexists with lamellar liquid-crystal phase. Marked temperature-dependent changes were observed when cubic phase coexists with hexagonal phase or lamellar-gel phases. This is the first report of cubic phases formed by codispersions of glycosphingolipids and phospholipids. The mechanism of cubic phase formation and the interaction between GlcCer and POPE is discussed in terms of the putative biological functions of glycolipids.

Time-resolved small-angle X-ray scattering and wide-angle X-ray diffraction studies on the nanostructure of melt-processable molecular composites

Novel melt-processable molecular composites were obtained from isotactic polypropylene (iPP) and liquid-crystalline oligoester (LCO). The nanostructure and thermal behaviour of molecular composites were examined by real-time synchrotron small-angle X-ray scattering and wide-angle X-ray diffraction methods, and differential scanning calorimetry. The synthesized oligoester, with low melting temperature (391 K), exhibits the ability to form a thermotropic mesophase. It was shown that strong rigid rod-like macromolecules of LCO are dispersed at the molecular scale in iPP matrix and act as reinforcing fibres.

Characterization of nano-structured poly(ε-caprolactone) nonwoven mats via electrospinning

Nano-structured poly(ε-caprolactone) (PCL) nonwoven mats were prepared by electrospinning process. In this study, three types of solution were used. One dissolved in only methylene chloride (MC), the second dissolved in mixture of MC and N, N-dimethylformamide (DMF), the third dissolved in mixture of MC and toluene. MC, toluene and DMF are a good, poor, and nonsolvent for PCL, respectively. For the MC only, electrospun fibers had very regular diameter of about 5500 nm, but electrospinng is not facilitated. For the mixture of MC and DMF, electrospinning is certainly enhanced as well as fiber diameter decreased dramatically as increasing DMF volume fraction. It was due to high electric properties of solution such as dielectric constant and conductivity. Whereas, as increasing toluene volume fraction, electrospinning is strictly restricted due to very high viscosity and low conductivity. As the results, it has regarded that solution properties is one of the important parameter in electrospinning. Properties such as conductivity, surface tension, viscosity and dielectric constant of the PCL solutions prepared from three types of solvent system were studied. The morphology, crystallinity and mechanical properties of electrospun PCL nonwoven mats were characterized by scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and universal testing method (UTM), respectively.

Control on the structure of poly(oxyethylene) with tri(oxyethylene) side chains for a polymer solid electrolyte

Structure of poly(oxyethylene) with tri(oxyethylene) side chains (TEC) doped with LiClO 4 was quantitatively evaluated by using a wide-angle X-ray diffraction (WAXD) method and the relation between the crystallinity of the branched polyether and the ionic conductivity was elucidated. By introducing tri(oxyethylene) side chains, the crystallinity of TEC became much lower than linear poly(oxyethylene) (PEO)and the ionic conductivity increased significantly. Further, the change of spherulitic structure was observed by using the polarized light microscope. The structure of the linear poly(oxyethylene) is the sheaflike spherulites and that of TEC is the spherulites which show the concentric extinction rings due to the influence of side chains. The structure of TEC doped with LiClO 4 at the concentration of [Li]/[-O-]=0.05 is the sheaflike spherulites again, but is different from that of poly(oxyethylene). The sizes of spherulites of TEC doped with LiClO 4 are smaller and the bundle of lamellae, which grew to the radial direction, is disordered and thicker than that of poly(oxyethylene). This is due to the presence of tri(oxyethylene) side chains and lithium salts between lamellae of poly(oxyethylene). From the oriented crystallization by uniaxial drawing or shearing, a “stacked lamellae” structure parallel to oriented direction is obtained. The structure may afford different ionic conductivities according to the direction of a material. In other words, anisotropic conductivity may be observed on this oriented material.

Cocrystallization behavior of poly(hexamethylene terephthalate- co-hexamethylene 2,6-naphthalate) random copolymers

A series of poly(hexamethylene terephthalate- co-hexamethylene 2,6-naphthalate) (P(HT- co-HN)) random copolymers were synthesized by melt polycondensation and characterized using 1H NMR spectroscopy and viscometry. Their cocrystallization behavior was investigated using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) method. Even though the P(HT- co-HN) copolymers synthesized are statistically random copolymers, they show a clear melting and a crystallization peak in DSC thermograms over the entire range of copolymer composition and have a minimum melting temperature in the plot of melting temperature versus copolymer composition. WAXD patterns of all the copolymer samples show sharp diffraction peaks and are largely divided into two groups, i.e. PHT type and PHN type crystals. In addition, WAXD patterns of the PHN type crystals are subdivided into two types of PHN α and PHN β according to the copolymer composition. These facts indicate that the P(HT- co-HN) copolymers show isodimorphic cocrystallization. The composition at which the crystal transition between PHT type and PHN type occurs is equivalent to the eutectic composition (22 mol% HN content) for the melting temperature. When the defect free energies were calculated by using the equilibrium inclusion model proposed by Wendling and Suter, the defect free energies in the case of incorporation of HT units in the PHN α and β crystals were higher than the case of incorporation of HN units in the PHT crystal lattice.

Studies on the interface of glass fiber-reinforced polypropylene composite

The interfacial characteristics of glass fiber-reinforced polypropylene (PP) are studied with polarized light microscopy, wide angle X-ray diffraction and single fiber fragmentation methods. Transcrystallites are generated at the interface of KH-550 treated glass fiber-reinforced PP when it is blended with maleic anhydride-grafted PP (MA-PP). MA-PP markedly enhanced the interfacial shear strength (IFSS) of the chemically treated glass fiber-reinforced PP composite. A fiber fracture model is proposed. IFSS around 4–7 MPa would be good choices for the system of KH-550 treated glass fiber and PP modified with MA-PP.

Time-resolved isothermal crystallization of absorbable PGA-co-PLA copolymer by synchrotron small-angle X-ray scattering and wide-angle X-ray diffraction

The isothermal crystallization behavior of absorbable dyed and undyed PGA-co-PLA copolymers was investigated by time-resolved simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) methods with synchrotron radiation. The morphological parameters extracted from time-resolved SAXS profiles show that long period and lamellar thickness decrease slightly after primary crystallization. The unit cell parameters a and b and the apparent lateral crystal sizes L110 and L020 were extracted from the corresponding WAXD profiles. A significant decrease in the unit cell parameters and a substantial increase in the apparent crystal sizes are seen during the initial crystallization stage. Both scattering invariant (Q from SAXS) and crystallinity (Xc from WAXD) results indicate that the crystallization rate is the fastest at 130°C. These copolymers show a bell-shape crystallization rate curve with temperature, where the dyed copolymer has a faster crystallization rate than the undyed one even though the inclusion of the low molecular weight organic dye is very small (ca. 0.2% by weight). We conclude that the dye molecule, which enhances the visibility during surgery, acts as a nucleating agent that increases the overall crystallization rate. The crystallization rate at 90°C is significantly slower than that at 130°C, however, the long period and lamellar thickness formed at 90°C are much lower than those formed at higher temperatures. The dyed and undyed PGA-co-PLA copolymers have almost the same morphological parameters at the same temperature. This indicates that morphological parameters of the lamellar structures in the polymers depend primarily on the crystallization temperature rather than on the crystallization rate. It is evident that the thermodynamic factor driven by temperature principally determines the lamellar morphology. The final unit cell parameters a and b and the final apparent crystal sizes all increase with temperature, indicating that crystal perfection prevails at high temperatures.

Crystal orientation function of poly(trimethylene terephthalate) by wide-angle x-ray diffraction

A wide-angle X-ray diffraction method for measuring poly(trimethylene terephthalate) (PTT) crystal orientation function was described. It was based on Wilchinsky's treatment of uniaxial orientation. Although PTT has a low symmetry triclinic cell only one equatorial reflection is needed for the measurement because the unit cell β-angle happened to be 90°, and there is a strong 010 reflection. The choice of unit cell parameters from the conflicting literature data and the reduction of Wilchinsky's equation into a simple form allowing the measurement of only one reflection were presented. The discrepancies between literature wide-angle X-ray and electron diffraction unit cell volumes and crystal densities were also discussed.

The Relationship Between Structures and In Vitro Properties of a Polyanhydride Implant Containing Gentamicin Sulfate

Laboratory scale injection-molding equipment was utilized to fabricate an implant consisting of poly(FAD:SA 1:1) and 20% (w/w) gentamicin sulfate. Characterizations were performed to determine the molecular weight and glass transition temperature of poly(FAD:SA 1:1). A study was carried out to investigate the relationships between the in vitro performance, morphology, and micro-structures of the molded implants. It was found that implants produced with different structures exhibited different physical integrities in water, i.e., cracking or non-cracking. For the non-cracking implants, a skin–core structure formed by an oriented skin layer was observed under a polarized light microscope. The same morphology was not seen in the cracking implants. The crystal orientation in the skin layer of the non-cracking implants was further identified using a wide-angle x-ray diffraction method (WAXD). No crystal orientation could be found in the cracking implants by WAXD. Furthermore, studies were carried out to evaluate the in vitro drug release for implants showing different degrees of integrity in water. The in vitro drug release of the cracking implants was markedly faster than that of the non-cracking implants due to the pronounced initial drug-burst effect as a result of crack formation in the implants.