Uniaxially aligned poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] thin films characterized by the X‐ray diffraction pole figure technique

Aligned thin films of the liquid‐crystalline polymer poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] were prepared, and the correlation between the optical anisotropy and the structural properties was shown. A series of samples with different thicknesses were prepared via a spin‐casting process on rubbed polyimide surfaces. The alignment of the polymer chains was obtained by a temperature treatment just below the clearing temperature. The degree of alignment was investigated with ultraviolet–visible absorption spectroscopy and in‐plane X‐ray diffraction. Independently, each technique revealed Hermans orientation functions in the range of 0.75–0.8. Surprisingly, a layer‐thickness dependence was not observed. In addition, the X‐ray diffraction pole figure technique revealed that the polymer chains were uniaxially aligned along the rubbing direction. The aligned films were in the nematic state, with the director elongated along the rubbing direction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fluorinated‐plasma modification of polyetherimide films

Ultem 1000 polyetherimide films prepared by cast-evaporating technique were covered with a 1H,1H,2H-tridecafluoro-oct-1-ene (PFO) plasma-polymerized layer. The effects of the plasma exposure time on the surface composition were studied by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and surface energy analysis. The surface topography of the plasma layer was deduced from scanning electron microscopy. The F/C ratio for plasma-polymerized PFO under the input RF power of 50 W can be as high as 1.30 for 480 s and ∼0.4–2 at % of oxygen was detected, resulting from the reaction of long-lived radicals in the plasma polymer with atmospheric oxygen. The plasma deposition of fluorocarbon coating from plasma PFO reduces the surface energy from 46 to 18.3 mJ m⁻². © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3579–3588, 2006     

X‐ray diffraction characterization of the structure of zein–Oleic acid films

Wide‐angle (WAXS) and small‐angle X‐ray scattering (SAXS) studies of dry granular zein, zein fibers, zein–oleic acid resin, and zein–oleic acid films are reported. WAXS patterns showed two diffuse rings for these samples indicative of noncrystalline structures. Measured d‐spacings of ∼ 4.6 Å and ∼ 10.5 Å were found for zein–oleic acid resins and films, consistent with the presence of α‐helical segments. The granular zein and zein fibers had ∼ 4.6‐Å and ∼ 9.5‐Å spacings. Neither the films nor the fibers showed evidence of orientation of the molecular axes. SAXS studies of zein–oleic acid films indicated that the structure of the films was affected by preparation method. Biaxially drawn resin films showed periodicities of ∼ 170 Å along the film surface direction and ∼ 135 Å in the thickness direction, while the cast films had weaker intensity periodicities of ca. 80 Å for all beam directions; a weak, diffuse 45‐Å spacing was also observed for both samples. The 170‐Å periodicity was present in the resin before deformation and following uniaxial deformation. No SAXS periodicity was observed for the granular zein or zein fibers. Several structural models are presented for the resin films that are consistent with reports in the literature that zein, in solution, consist of prism‐like particles consisting of four or more molecules. ? 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1267‐1281, 1999     

Simulation Program for Element Specific X‐Ray Tomography at a 15 MeV High Power Electron Linac

A new beam line was developed and built at the high power electron linac of the Ghent University for tomographic purposes. It will be used for polychromatic γ‐tomography and for element specific, high spatial resolution tomography. In this paper we will discuss the latest progress and results for high resolution element specific tomography. First we will give an overview of the facility and geometry of the set‐up and then give an overview of the simulation software for the beam line. Finally we present some experimental results of element sensitive tomography to demonstrate the power of the NDT technique for chemical engineering.     

Moisture Profiles Determination During Convective Drying Using X‐Ray Microtomography

The knowledge of internal moisture profiles which develop during drying is essential for model validation purposes, but they are difficult to determine experimentally. This paper shows that X‐ray microtomography, together with image analysis, provides an accurate, non destructive and easy to use technique to determine moisture profiles. Results reported concern the drying of wastewater sludges whose management is becoming a real environmental challenge. An analysis of the development of moisture gradients at the sample external wall shows an influence of drying operating conditions. Finally, mass diffusion coefficients are estimated from the knowledge of both the moisture gradients and the drying flux.     

Microstructural Evolution of Isotactic‐Polypropylene during Creep: An In Situ Study by Synchrotron Small‐Angle X‐Ray Scattering

The structure evolution of isotactic‐polypropylene during creep is investigated by in situ synchrotron small‐angle X‐ray scattering. During primary creep, strain grows nonlinearly to a value less than 15%. The long period in loading direction (L _∥) increases with time, whereas the long period perpendicular to the loading direction (L _⊥) decreases slightly. During the secondary creep, strain increases linearly with time. L _∥ and L _⊥ show the same tendency with strain. The increase of the long period is caused by lamellae thickening, which is a kind of cooperative motion of polymer chains with their neighbors at the lamellae surface. Moreover, the growth rate of L _∥ is larger than that of L _⊥, indicating that the orientation of molecular chains along the loading direction decreases the energy barrier of the cooperative motion. During tertiary creep, strain grows dramatically in a short time. In this step, the lamellae are tilted, rotated, and then disaggregated. In addition, a fibrillar structure is formed during lamellae breaking. The length of the fibrillar structure increases from 364 to 497 nm while its width stays at 102 nm with increasing creeping time.     

Cocrystallization behavior of poly(n‐docosyl acrylate) with n‐docosanoic acid by X‐ray and differential scanning calorimetry studies

Cocrystallization behavior of comb‐like poly(n‐docosyl acrylate) (PDA) with n‐docosanoic acid (C₂₂) has been studied by means of differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) methods. The DSC curves of blended samples of neat PDA with C₂₂ show the characteristic melting endotherms that correspond to the melting of the crystallites. DSC measurements of PDA/C₂₂ blends also suggest the existence of another crystalline form induced by the addition of the C₂₂. From the XRD measurements, the existence of hexagonally‐packed crystalline lattice and the phase behavior of PDA/C₂₂ blends at different mole percent are confirmed. Thermal degradation behavior of PDA and its corresponding blends with C₂₂ is studied by thermogravimetric analysis. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2140–2146, 2005     

In Situ X‐Ray Diffraction and Stress Analysis of Solid Oxide Fuel Cells

To increase the long term stability and performance of solid oxide fuel cell (SOFC) materials, it is important to understand the main degradation processes in their functional layers. In this work, the interface between electrolyte and anode material was investigated by in situ X‐ray diffraction (XRD) stress and phase analysis. It has been found that the determining process for the initial degradation of SOFC is the reduction of the anode material with hydrogen. During this process a tensile strength of 600–700 MPa is measured. These stresses are induced in the electrolyte material and produce crack networks. The reduction from nickel oxide to pure nickel was monitored by in situ phase analysis. This reaction induces tensile stress at the interface between electrolyte and anode. The stress produced in the electrolyte material was also confirmed by the observation of crack networks detected using scanning electron microscopy (SEM). Finally, the reducing process was optimized using different process gases, decreasing the destructive tensile stress level.     

Structure–property relationship of polyimide fibers containing ether groups

The copolyimide (co‐PI) fibers with outstanding mechanical properties were prepared by a two‐step wet‐spinning method, derived from the design of combining 4,4′‐oxydianiline (ODA) with the rigid 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)/p‐phenylenediamine (p‐PDA) backbone. The mechanical properties of PI fibers were drastically improved with the optimum tensile strength of 2.53 GPa at a p‐PDA/ODA molar ratio of 5/5, which was approximately 3.7 times the tensile strength of BPDA/p‐PDA PI fibers. Two‐dimensional wide‐angle X‐ray diffraction indicated that the highly oriented structures were formed in the fibers. Two‐dimensional small‐angle X‐ray scattering revealed the existence of the needle‐shaped microvoids aligned parallel to the fiber axis, and the introduction of ODA led to the reduction in the size of the microvoids. As a result, the significantly improved mechanical properties of PI fibers were mainly attributed to the gradually formed homogeneous structures. The co‐PI fibers also exhibited excellent thermal stabilities of up to 563°C in nitrogen and 536°C in air for a 5% weight loss and glass transition temperatures above 279°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42474.     

Recent developments in polymer applications of synchrotron small‐angle X‐ray scattering

Synchrotron radiation facilities have been established and become very familiar in the polymer community not only from academic but also industrial viewpoints. It is not so unusual now to conduct simultaneous measurements of small‐angle X‐ray scattering (SAXS) with other techniques such as wide‐angle X‐ray scattering, stress–strain, light scattering, and so forth. New techniques have also been established and have become more familiar in recent years. In this review, recent developments in polymer applications of synchrotron SAXS are summarized. Instrumental developments and progress in data analyses are reviewed from the following aspects: ultra‐small‐angle X‐ray scattering, anomalous SAXS, X‐ray photon correlation spectroscopy, new types of simultaneous measurements, grazing‐incidence SAXS, new trends in nanoparticle analyses and industrial applications. © 2016 Society of Chemical Industry     

Design of an X‐Ray Powder Diffraction Probe for Multi‐Channel Application: Proof of Principle

The design of an X‐ray powder diffraction probe and its integration with a multi‐channel reactor system for potential application in high‐throughput experimentation is presented. The working principle of the apparatus is exemplified by measurements of corundum and of the phase change observed when oxidizing vanadium(III) oxide (V₂O₃) in air during heating up to 450 °C. The phase transformations of the parent material were monitored by phase identification of the crystalline intermediate vanadium(IV) oxide (VO₂) and the final product vanadium(V) oxide (V₂O₅).     

Low‐temperature thermal graft copolymerization of 1‐vinyl imidazole on fluorinated polyimide films with simultaneous lamination of copper foils

A simple technique of thermal graft copolymerization of 1‐vinyl imidazole (VIDZ) on pristine and argon plasma pretreated fluorinated polyimide (FPI) films with simultaneous lamination of copper foils was demonstrated. The simultaneous thermal grafting and lamination process was carried out in the temperature range of 80–140°C under atmospheric conditions and in the complete absence of a polymerization initiator. Three different FPI samples of different chemical structures were employed in the present study. An optimum T‐peel strength about 15 N/cm was achieved for the copper/FPI laminate. The adhesion strength, however, decreased with increasing fluorine content in the FPI film. The onset of cohesive failure occurred in the FPI film for assemblies with T‐peel strength greater than 6 N/cm. The T‐peel strengths are reported as a function of the argon plasma pretreatment time of the FPI films and thermal lamination temperature. The adhesion strengths were compared to that of the similarly prepared copper/polyimide (Kapton HN) laminate. Time‐dependent water contact angle (Θ) measurements indicated that the surfaces of FPI films are significantly more hydrophobic and more resistant to water diffusion or hydration than the Kapton HN films. The surface compositions of the pristine FPI films, as well as the delaminated FPI films and copper foils were studied by X‐ray photoelectron spectroscopy. The thickness of the graft VIDZ polymer layer was in the order of 200 nm, as derived from the cross‐sectional view of the scanning electron micrograph. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1478–1489, 1999     

Synthesis and Characterization of 3,4,5‐Triamino‐1,2,4‐Triazolium 5‐Nitrotetrazolate

3,4,5‐Triamino‐1,2,4‐triazolium 5‐nitrotetrazolate ( 2 ) was synthesized in high yield from 3,4,5‐triamino‐1,2,4‐triazole (guanazine) ( 1 ) and ammonium 5‐nitrotetrazolate. The new compound 2 was characterized by vibrational (IR and Raman) and multinuclear NMR spectroscopy (¹H, ¹³C, ¹⁵N), elemental analysis and single crystal X‐ray diffraction (triclinic, P(‐1), a=0.7194(5), b=0.8215(5), c=0.8668(5) nm, α=75.307(5), β=70.054(5), γ=68.104(5)°, V=0.4421(5) nm³, Z=2, ϱ=1.722 g cm⁻¹, R₁=0.0519 [F>4σ(F)], wR₂(all data)=0.1154). The ¹⁵N NMR spectrum and X‐ray crystal structure (triclinic, P‐1, a=0.5578(5), b=0.6166(5), c=0.7395(5) nm, α=114.485(5)°, β=90.810(5)°, γ=97.846(5)°, V=0.2286(3) nm³, Z=2, ϱ=1.658 g cm⁻¹, R₁=0.0460 [F>4σ(F)], wR₂(all data)=0.1153) of 1 were also determined.     

Peak‐fitting analysis of cotton fiber powder X‐ray diffraction spectra

The precision and accuracy of diffraction peak positions resolved from the powder X‐ray diffraction spectra of cotton fibers by means of the residuals peak‐fitting procedure of a commercial peak‐fitting software package (PeakFit®) was investigated to explore the potential of such programs in providing reliable data that are not readily apparent in diffuse X‐ray spectra. Each intensity spectrum was fitted by employing a Gaussian function as the peak profile. The precision of 15 pairs of the resolved diffraction peaks is 0.0017 mm; 9 of the 15 pairs fall into the 99% confidence interval. The precision in 2θ of four commonly identified peaks through four independent fittings is from 0.002 to 0.014°. The 2θ accuracy of the resolved peaks is good in comparison to data calculated for both the traditionally accepted and the more recently revised concepts of the cellulose I crystal structure. A peak resolved at about 15.3° may be attributed to the triclinic crystal structure component of cellulose I. Although distinct peaks are not readily apparent in the diffuse spectrum of cellulose, peak‐fitting procedures may provide additional data for structure determination. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2019–2024, 2004     

On the fractal character of polymer spherulites: an ultra‐small‐angle X‐ray scattering study of poly[(R)‐3‐hydroxybutyrate]

Ultra‐small‐angle X‐ray scattering (USAXS) and small‐angle X‐ray scattering (SAXS) measurements are presented for poly[(R)‐3‐hydroxybutyrate] (PHB) crystallized at room temperature. The USAXS patterns indicated that the spherulites had a radially orientated fibrillar nanostructure with fractal geometry over a length scale ranging from 12 nm up to at least 300 nm, with a mass fractal dimension of approximately 2.7 in aged samples. The SAXS patterns indicated that the fibrils themselves were built up of bundles of crystalline lamellae separated by layers of disordered material, with a period length of approximately 6 nm. The SAXS measurements during primary crystallization gave an initial fractal dimension of 4 during spherulite growth, due to the sharp phase boundary between the spherulites and the melt. Copyright © 2004 Society of Chemical Industry     

Structural properties of CrF3‐ and MnCl2‐filled poly(vinyl alcohol) films

Poly(vinyl alcohol) (PVA) films filled with different amounts of CrF₃ and MnCl₂ were prepared by the casting method. Differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) analysis were used to study the changes in the structure properties that occurred because of filling. The changes occurring in the measured parameters with increasing filler contents were interpreted in terms of the structural modification of the PVA matrix. All the studied samples had a main melting temperature due to the main crystalline phase of PVA. The intensity and position of this peak depended on the filling level. However, the samples of CrF₃‐filled PVA films with a filling level greater than or equal to 10 wt % revealed another melting temperature, which indicated the presence of a new crystalline phase in addition to the main crystalline phase. The changes that occurred in the degree of crystallinity of the studied samples were examined. The calculated degree of crystallinity was formulated numerically to be an exponential function of the filling level. The XRD patterns of the studied samples confirmed the DSC results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1115–1120, 2003     

Study of the degree of crystallinity in eudragit/poly(methyl methacrylate) polyblends by X‐ray diffraction

Plaques of blends of Eudragit RL 100 (EU) and poly(methyl methacrylate) (PMMA) with different weight‐per‐weight ratios were prepared by compression molding at 150°C. The X‐ray diffraction profiles of the blends were studied and compared, and the interplanar distance, crystallite size, and crystallinity were computed for various peaks. The Eu/PMMA blend with a 70:30 (w/w) ratio had the maximum crystallinity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1835–1838, 2005     

Amino‐functionalized multiple‐walled carbon nanotubes‐polyimide nanocomposite films fabricated by in situ polymerization

For the preparation of high‐quality polymeric carbon nanocomposites, it is required that carbon nanotubes are fully compatible with matrix polymers. For this purpose, amino‐functionalized multiple‐walled carbon nanotubes (a‐MWNTs) were synthesized. The a‐MWNTs/polyimide nanocomposite films were prepared through in situ polymerization. According to the spectroscopic characterizations, the a‐MWNTs were homogeneously dispersed in the nanocomposite films as the acid‐functionalized MWNTs. The mechanical properties of the polyimide composite were also studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

In situ small angle X‐ray scattering study on structural evolution of crosslinked polytetrafluoroethylene during deformation

The structural evolution of virgin and crosslinked polytetrafluoroethylene (PTFE) during stretching was studied by in situ synchrotron small‐angle X‐ray scattering (SAXS). Both yield and tensile stress of crosslinked PTFE increased with increasing crosslinking density. During stretching, for virgin PTFE, amorphous chains gradually turned to tensile direction at early stage, perpendicularly arranged lamellar stacks appeared at high strains (>140%). While for crosslinked PTFE, lamellar structure was observed even at lower strains; with increasing irradiation dose, the lamellar structure became obvious and the long period decreased. Four‐point SAXS patterns were observed only in 3000kGy‐dosed PTFE during deformation, which indicated that an alternately tilted lamella arrangement called herringbone structure was formed. Radiation dose induces crosslinked networks formed, which can carry part of local stress during deformation, resulting in the increase of yield and tensile stress. Crosslinking density is an important factor on structural evolution. In addition, a deformation mechanism of different crosslinked PTFE is proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39883.