Wide-angle X-ray Diffraction Patterns Research Articles

Biobased odd–odd poly(propylene dicarboxylate)s

Biobased odd–odd poly(propylene dicarboxylate)s, based on 1,3-propanediol and three odd diacids [i.e., glutaric acid (C5), pimelic acid (C7) or azelaic acid (C9)], have been synthesized and analyzed, in order to study the effect of chain length of aliphatic diacids on thermal properties. Crystallization and melting behaviors were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), temperature-modulated differential scanning calorimetry (TMDSC) and polarized optical microscope (POM). DSC results suggested that the crystallization ability increases with the increasing chain length. WAXD patterns of the three polyesters showed a similar crystal structure. In DSC heating curves after isothermal crystallization of the samples, three endothermic peaks for the polyesters at shorter chain length (C5, C7) and at most four endothermic peaks for longer-chain-length polyester (C9) were displayed, and the mechanism of the multiple melting phenomenon was discussed. One or two exothermic peaks can be seen for shorter (C7) or longer (C9) polyester in the non-reversible heat flows of TMDSC, respectively, which evidenced once or twice melting–recrystallization–remelting processes occurring during melting heating. Finally, POM observation indicated that the spherulitic growth rate increases with the increasing chain length. Besides, ring-banded structures were observed in short-chain-length (C5, C7) samples, but C9 aliphatic polyester.

Tensile study of melt-spun poly(3-hydroxybutyrate) P3HB fibers: Reversible transformation of a highly oriented phase

Poly-3-hydroxybutyrate (P3HB) typically crystallizes into the orthorhombic α-form. The additional intense and rather broad equatorial reflection in wide-angle X-ray diffraction (WAXD) patterns seen in our melt-spun P3HB fibers cannot be attributed to the α-form crystals. We propose that a non-crystalline mesophase, which consists of disordered but highly oriented and stretched molecules located between α-crystals, leads to the observed broad equatorial reflection. We show that the transformation of this mesophase from and into the α-form phase is partially reversible under cyclic tensile loading. Structure factor calculations, which are based on atomic positions from molecular dynamics simulations of a set of stretched P3HB molecules, support this model. The WAXD patterns were analyzed with azimuthal, radial, equatorial and meridional scans and the changes in the crystal orientation, changes in the percentages of individual phases and changes in the α-crystal lattice spacings were analyzed as a function of the applied tension. Changes in long spacings, crystal sizes and coherence lengths under cyclic loading were determined with small-angle X-ray scattering (SAXS) measurements. The long spacing between α-crystals increases when tensile stress is applied and it snaps back to the original spacing when the tensile stress is released.

Biaxial ordering in the supercooled nematic phase of bent-core mesogens: effects of molecular symmetry and outer wing lateral groups

ABSTRACT In previous research, we have found that the incorporation of three lateral substituents on bent-core oxadiazole-based liquid crystals has allowed for the presence of a nematic phase that supercooled to room temperature. X-ray diffraction (XRD) studies of these derivatives have confirmed that the nematic phase consists of cybotactic clusters. Moreover, the wide-angle XRD pattern showed a splitting indicative of local biaxial ordering within this phase. In this paper, we report the phase behaviour of two series of compounds that contain up to four lateral methyl groups. In one series, the arrangement of the lateral groups is symmetrical, and in the other case, the groups are not symmetrically distributed. All of the non-symmetric derivatives supercool to room temperature in the nematic phase, while symmetric derivatives tend to crystallise well above room temperature. XRD analysis of all of these compounds indicates the presence of cybotactic order. However, a splitting of the wide-angle XRD pattern is observed only in derivatives with lateral groups on the outer benzene rings, regardless of their supercooling behaviour, indicating the crucial influence of these substituents on the molecular packing.

Diversified α-phase nanostructure of isotactic polypropylene under cylindrical confinement via cross diffraction analysis

Understanding polymer nanostructures is a prerequisite to manipulate their physical properties. Molecular self-assembly under confinement effectively generates novel polymer nanostructures. However, in one confined system, diffraction signals of different nanostructures are merged in a typical two-dimensional (2D) wide-angle X-ray diffraction (WAXD) measurement. For comparison, selected-area electron diffraction (SAED) of transmission electron microscopy can precisely capture the “local” diffraction signal of an individual nanoscale entity. Here, using isotactic polypropylene (i-PP) as a model polymer, we have demonstrated a cross-analysis of global X-ray and local electron diffraction results to fully reveal the structural details of i-PP nanorods. For the first time, we have decomposed completely the “mixed” 2D WAXD patterns of i-PP nanorods into five types of α-phase nanostructures: (a). Left-tilted daughter crystals; (b) Right-tilted daughter crystals; (c) Double-tilted daughter crystals; (d) a*-axis oriented crystals; (e) b-axis oriented crystals.

Crystallization of Long-Spaced Precision Polyacetals I: Melting and Recrystallization of Rapidly Formed Crystallites

Rapidly melt-crystallized polyethylenes with acetal groups (−O–CH2–O−) precisely spaced by 12, 18, 19, or 23 methylene backbone carbons exhibit two reorganizations and three melting endotherms on heating at relatively low heating rates. Real-time wide-angle X-ray diffraction (WAXD) experiments further confirm that these transitions are associated with a reorganization to a different crystalline structure. The differential scanning calorimetry endotherms are associated with melting of the initially formed disordered (or hexagonal) phases, followed by melting of Form I and by melting of Form II crystals with increasing temperature. In parallel with these structural changes, the long spacing undergoes a discrete step increase at the polymorphic transitions. Upon the transition from disordered to Form I crystals, the core crystal thickness increases by one repeating unit, whereas the crystal thickness remains basically unchanged during the transition from Form I to Form II crystallites. The effect of even vs odd CH2 spacer on the observed melting temperatures is prevalent for spacer <10 CH2 units. The even or odd number of methylenes between acetals also affects the type and kinetics of packing assembly in layered crystallites. Although a disordered mesomorphic-like structure develops under fast cooling in odd-spaced polyacetals (PA-19, PA-23), the formation of Form I crystals cannot be bypassed in PA-12 and PA-18. Furthermore, some differences are also found in the WAXD patterns of Form II between odd- and even-spaced polyacetals, denoting that staggering of the acetals in the crystallites is affected by the configuration of consecutive acetals with respect to the methylene sequence.

Biobased Engineering Thermoplastics: Poly(butylene 2,5-furandicarboxylate) Blends.

Poly(butylene 2,5-furandicarboxylate) (PBF) constitutes a new engineering polyester produced from renewable resources, as it is synthesized from 2,5-furandicarboxylic acid (2,5-FDCA) and 1,4-butanediol (1,4-BD), both formed from sugars coming from biomass. In this research, initially high-molecular-weight PBF was synthesized by applying the melt polycondensation method and using the dimethylester of FDCA as the monomer. Furthermore, five different series of PBF blends were prepared, namely poly(l-lactic acid)–poly(butylene 2,5-furandicarboxylate) (PLA–PBF), poly(ethylene terephthalate)–poly(butylene 2,5-furandicarboxylate) (PET–PBF), poly(propylene terephthalate)–poly(butylene 2,5-furandicarboxylate) (PPT–PBF), poly(butylene 2,6-naphthalenedicarboxylate)-poly(butylene 2,5-furandicarboxylate) (PBN–PBF), and polycarbonate–poly(butylene 2,5-furandicarboxylate) (PC–PBF), by dissolving the polyesters in a trifluoroacetic acid/chloroform mixture (1/4 v/v) followed by coprecipitation as a result of adding the solutions into excess of cold methanol. The wide-angle X-ray diffraction (WAXD) patterns of the as-prepared blends showed that mixtures of crystals of the blend components were formed, except for PC which did not crystallize. In general, a lower degree of crystallinity was observed at intermediate compositions. The differential scanning calorimetry (DSC) heating scans for the melt-quenched samples proved homogeneity in the case of PET–PBF blends. In the remaining cases, the blend components showed distinct Tgs. In PPT–PBF blends, there was a shift of the Tgs to intermediate values, showing some partial miscibility. Reactive blending proved to improve compatibility of the PBN–PBF blends.

Synthesis and Properties of Poly(butylene carbonate-co-spirocyclic carbonate)

Poly(butylene carbonate)(PBC) has significantly promising applications as a degradable material in the field of polymers, while its poor thermal performance and low crystallization rate are its main defects. To overcome these shortcomings, a series of poly(butylene carbonate-co-spirocyclic carbonate)(PBSC) copolymers were synthesized from diphenyl carbonate, 1,4-butanediol and spiroglycol via two-step polycondensation reactions, using magnesium oxide as a catalyst. Differential scanning calorimetry(DSC) results indicated that the glass transition temperature(Tg) values of PBSC copolymers were enhanced from −19 °C to 56 °C with rising the spiroacetal moiety content. Thermogravimetric analysis(TGA) results showed that the resulting PBSCs have a higher thermal stability than that of poly(butylene carbonate). Wide angle X-ray diffraction(WXRD) patterns were characterized to investigate the crystallization behaviour of PBSCs. Tensile testing demonstrated that copolymerization of spiroacetal moieties into PBC chains imparted PBSC with favourable mechanical performance. Typically, PBSC30 had a tensile modulus of (1735±430) MPa, a tensile strength of (42±5) MPa and an elongation of 504%±36%.

Effect of ripening on in vitro digestibility and structural characteristics of plantain (Musa ABB) starch

This study focused on the effect of ripening on in vitro digestibility and the multi-scale structural characteristics of plantain starch. It was shown that the RS content of plantain starch gradually decreased during ripening process, while RDS and SDS contents increased. Scanning electron micrographs showed the layer-by-layer degradation of the surfaces of starch granules. The transformation from CB-type to CA-type crystalline structure of starch was revealed by wide angle X-ray diffraction patterns. Relative crystallinity, IR ratio 1045/1022 and the apparent amylose content all decreased with increasing maturity. Meanwhile, branched chain length distributions of amylopectin indicated that the content of short chain increased and that of long chain decreased, leading to the changes of digestion performance. In addition, the serious damage to amorphous region in semi-crystalline lamellae and amorphous growth ring was caused. All above factors contributed to the decrease of plantain starch resistance to digestion with increasing maturity. This work provides a fundamental understanding of the changes that plantain starch undergoes during ripening.

Preparation and Properties of High-performance Polyimide Copolymer Fibers Derived from 5-Amino-2-(2-hydroxy-5-aminobenzene)-benzoxazole

A series of polyamic acid copolymers (co-PAAs) with para-hydroxyl groups was synthesized using two diamine monomers, namely p-phenylenediamine (p-PDA) and 5-amino-2-(2-hydroxy-5-aminobenzene)-benzoxazole (m-pHBOA), of different molar ratios through copolymerization with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) in N,N-dimethyacetamine (DMAc). The co-PAA solutions were used to fabricate fibers by dry-jet wet spinning, and thermal imidization was conducted to obtain polyimide copolymer (co-PI) fibers. The effects of the m-pHBOA moiety on molecular packing and physical properties of the prepared fibers were investigated. Fourier transform infrared (FTIR) spectroscopic results confirmed that intra/intermolecular hydrogen bonds originated from the hydroxyl group and the nitrogen atom of the benzoxazole group and/or the hydroxyl group and the oxygen atom of the carbonyl group of cyclic imide. As-prepared PI fibers displayed homogenous and smooth surface and uniform diameter. The glass transition temperatures (Tgs) of PI fibers were within 311−337 °C. The polyimide fibers showed 5% weight loss temperature (T5%) at above 510 °C in air. Two-dimensional wide-angle X-ray diffraction (WXRD) patterns indicated that the homo-PI and co-PI fibers presented regularly arranged polymer chains along the fiber axial direction. The ordered molecular packing along the transversal direction was destroyed by introducing the m-pHBOA moiety. Moreover, the crystallinity and orientation factors increased with increasing draw ratio. Small-angle X-ray scattering (SAXS) results showed that it is beneficial to reduce defects in the fibers by increasing the draw ratio. The resultant PI fibers exhibited excellent mechanical properties with fracture strength and initial modulus of 2.48 and 89.73 GPa, respectively, when the molar ratio of p-PDA/m-pHBOA was 5/5 and the draw ratio was 3.0.

Aggregation behavior of the amyloid model peptide NACore

AbstractThe aggregation of the 11 residue long NACore peptide segment of α-synuclein (68-GAVVTGVTAVA-78) has been investigated using a combination of cryogenic transmission electron microscopy (cryo-TEM), small- and wide-angle X-ray scattering, and spectroscopy techniques. The aqueous peptide solubility is pH dependent, and aggregation was triggered by a pH quench from pH 11.3 to approximately pH 8 or 6, where the average peptide net charge is weakly negative (pH 8), or essentially zero (pH 6). Cryo-TEM shows the presence of long and stiff fibrillar aggregates at both pH, that are built up from β-sheets, as demonstrated by circular dichroism spectroscopy and thioflavin T fluorescence. The fibrils are crystalline, with a wide angle X-ray diffraction pattern that is consistent with a previously determined crystal structure of NACore. Of particular note is the cryo-TEM observation of small globular shaped aggregates, of the order of a few nanometers in size, adsorbed onto the surface of already formed fibrils at pH 6. The fibrillation kinetics is slow, and occurs on the time scale of days. Similarly slow kinetics is observed at both pH, but slightly slower at pH 6, even though the peptide solubility is here expected to be lower. The observation of the small globular shaped aggregates, together with the associated kinetics, could be highly relevant in relation to mechanisms of secondary nucleation and oligomer formation in amyloid systems.

Processing and strain induced crystallization and reinforcement under strain of poly(1,4-cis-isoprene) from Ziegler–Natta catalysis, hevea brasiliensis, taraxacum kok-saghyz and partenium argentatum

Abstract Strain induced crystallization and reinforcement were studied for poly(isoprene)s from the following sources: Ziegler–Natta catalysis, hevea brasiliensis (HNR), taraxacum kok-saghyz (TKS), known as the russian dandelion, partenium argentatum (GR), known as guayule. Two HNR samples were studied, with high (HNR-H) and low (HNR-L) molar mass. Investigated guayule samples were: as isolated from the latex (GR-R) and after extraction with acetone (GR-P). All of the samples had weight average molar mass higher than 1.5 × 106 Da. TKS was found to be the most stereoregular sample, with undetectable amounts of stereoerrors. Wide angle X-Ray diffraction patterns were collected on samples, unstretched after processing and during stretching, up to 5 as the strain ratio. Quasi-static tensile measurements were performed. HNR and GR-P exhibited rubber crystallinity already in the undeformed state and the orientation of their crystalline phase remained low also for the highest strain ratios. GR-R and TKS were amorphous at low strain and developed highly oriented crystalline phases under stretching. TKS developed extraordinary mechanical reinforcement under stretching: stresses at large elongations were much higher than those obtained with HNR. It is thus shown that the formation of highly oriented crystalline phases brings large mechanical reinforcement. In conclusion, an amorphous NR sample from a natural source, such as TKS, which has high molar mass and does not contain non rubber components which could act as plastifiers, is able, under stretching, to develop crystallinity and a high degree of axial orientation. Crystallization occurs at high strain ratio, when the chains are prevailingly aligned. The biosynthesis of TKS is likely to play a strategic role, as it promotes the chain end crosslinking of the polymer chains.

Crystallization of poly(L-lactic acid)/poly(D-lactic acid) blend induced by organic solvents

Crystallization of amorphous poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) blend has been investigated by immersion in various organic solvents, acetone, ethyl acetate, tetrahydrofuran (THF), toluene, o-xylene, o-dichlorobenzene, and benzene. Crystalline structure of the blend samples was studied by wide angle X-ray diffraction pattern and differential scanning calorimetry measurement. Immersion of the amorphous blend sample in the solvents, except o-xylene, induced the crystallization of both the homo- and stereocomplex (SC) crystals of PLA. Among the used solvents, benzene, THF, and acetone were effective to form the SC crystal. Increase in the conducting temperature accelerated the formation of the SC crystal. The crystallization of the amorphous PLLA/PDLA blend has been also investigated by exposing to vapor of some organic solvents, acetone, THF, benzene, and chloroform. The vapor of chloroform induced crystallization of the SC crystal effectively. High compatibility, close solubility parameter, of PLA and the solvent should be essential to induce effective formation of the SC crystal by the vapor of the solvents.

Triaxially oriented shape memory natural rubber

Shape memory natural rubber (SMNR) is crystalline natural rubber (NR) which is stable at room temperature even after releasing from tensile force. In this study, preparation of triaxially oriented SMNR and its properties are reported. A series of wide-angle X-ray diffraction (WAXD) patterns was successfully obtained from this sample by changing the zone axis. The clear WAXD pattern corresponding to hk0 reciprocal lattice was also successfully obtained. The lattice constants of NR crystal reported in the previous studies were compared with those estimated from the specimen free from tensile stress, and as a result, distortion of the crystal lattice was found to be negligible. The triaxially oriented SMNR is thought to be useful for future refinement of crystal structure of NR. In the DSC measurements, multiple melting peaks of the crystallized SMNR appeared at temperature much higher than reported equilibrium melting temperature. An unidentified step similar to glass transition was also found in the DSC traces at about 20 °C.

Structural study of the ordering processes of cold drawn trans-1,4-polyisoprene samples in the heating process on the basis of wide- and small-angle X-ray scattering measurements

The regularization processes of the TPI glasses drawn at the various low temperatures were investigated by performing the temperature-dependent simultaneous measurements of the 2-dimensional wide-angle and small-angle X-ray scattering patterns. The glassy sample drawn below the cold crystallization temperature but above the glass transition temperature (-70°C) showed the disordered β form, which was found to transform to the regular β form at around -30°C. On the contrary, when we decreased the stretching temperature furthermore; for example -60 and -70°C, it gave the disordered α form. This disordered form transforms to the regular α form by heating to around 30°C. The small-angle X-ray scattering patterns were found to change in parallel with the wide-angle X-ray diffraction pattern changes, revealing a correlation between the crystalline phase transition and higher-order structure change in these regularization processes. These paracrystalline are packed in the smaller crystal cell than the regular form.

Enhanced piezoelectric output of the PVDF-TrFE/ZnO flexible piezoelectric nanogenerator by surface modification

In this paper, ZnO nano-particles (NPs) were modified by adding a dispersant (n-propylamine, PA) and a silane coupling agent (1H, 2H, 1H, 2H, Perfluorooctyltriethylsilane, PFOES) simultaneously. Further, the PVDF-TrFE/modified ZnO composite films with high crystallinity and large specific surface area were prepared, which acted as the active layer of the piezoelectric nanogenerator (PENG). Four species of films, pure PVDF-TrFE, PVDF-TrFE/ZnO, PVDF-TrFE/ZnO@PA and PVDF-TrFE/ZnO@PA@PFOES were marked P-0-0-0, P-Z-0-0, P-Z-P-0 and P-Z-P-P, respectively. The crystalline phases of the films were determined by Fourier infrared spectroscopy (FT-IR) and wide-angle X-ray diffraction (WXRD). Scanning electron microscope (SEM), Laser scanning confocal microscope (LSCM), Atomic force microscope (AFM) and water contact angle (WCA) measurements were employed to analyze the surface morphology of the films. The thermal properties of the materials were characterized with a differential scanning calorimeter (DSC). From the FTIR spectra and WXRD pattern, it was notable that the modified ZnO NPs promoted the crystallization of β-phase. The results showed that the crystallinity of P-Z-P-P was increased by 36.12% compared to P-0-0-0. Combined with the results of SEM, LSCM and AFM, it can be concluded from WCA that modified ZnO NPs can increase the specific surface area of the film. The piezoelectric strain constant d33 value of P-Z-P-P film was 73.5% higher than that of P-0-0-0 film, and the output voltage value of ITO/P-Z-P-P/Au PENG increased 24.4% than that of ITO/P-0-0-0/Au PENG. After 1000 cycles of testing, the output voltage of the ITO/P-Z-P-P/Au PENG has been maintained at 2.40 V, indicating that the generator exhibited the high mechanical endurance. By clarifying the mechanism of surface modification, it can be concluded that enhanced piezoelectric output of the PENG is contributed to both higher β-phase content and larger charge collecting area by surface modification.

Effect of Simultaneous Use of Silica and Nanoclay in Rubber Compounds Based on Nitrile Rubber

The synergistic effect of simultaneous use of two reinforcing fillers in rubber compounds based on Acrylonitrile Butadiene Rubber (NBR) was investigated with mechanical and vulcanisation characteristics of the rubber compounds. The Wide-Angle X-ray Diffraction (WAXD) patterns showed that in hybrid compounds, no obvious peaks appeared. This indicated that the nanoclay was exfoliated. These results revealed that addition of the reinforcing filler, either nanoclay or silica, shortened the optimum cure time (t90) and also scorch time (ts1) of samples compared to that of pure NBR compound. In hybrid compounds, the reduction in optimum cure time and scorch time was higher than that of for silica-filled NBR or nanoclay-filled NBR compounds. This can be attributed to the synergistic effect between nanoclay and silica as two reinforcing agents in NBR compounds. Regardless the composition of the reinforcing filler, an increase of the relaxed storage modulus was observed, while the tand value was gradually decreased. For hybrid samples, the experimental values of dynamic modulus showed a positive deviation from the values obtained from the Modified Guth model. Hybrid compounds showed higher burst strength compared to silica or nanoclay filled NBR compounds.

Effects of Drawing and Heat-Treatment Conditions on the Structure and Mechanical Properties of Polyhydroxyamide and Polybenzoxazole Fibers

We report the preparation of polybenzoxazole (PBO) fiber from polyhydroxyamide (PHA) precursor fiber which is free from strong acid such as polyphosphoric acid. We prepared the PHA fibers with different spin-draw ratios (SDRs) using a wet-spinning method and the PBO fibers with an SDR of 3.5 (SDR-3.5 PBO fibers) were prepared by various heat-treatment temperatures, and investigated their morphology, crystalline structure, and mechanical properties. The simultaneous thermogravimetric analysis-mass spectrometry (STA-MS) and field-emission scanning electron microscopy (FE-SEM) results confirmed that the diameter of the SDR-3.5 PBO fiber was much smaller than that of the SDR-3.5 PHA fiber, due to the release of water during the thermal cyclization reaction which forms the PBO structure. The wide-angle Xray diffraction (WAXD) pattern of the SDR-3.5 PBO fiber heat-treated at 350 °C (SDR-3.5 PBO 350 fiber) showed two peaks, at 2θ=14.83 ° and 24.38 °, and the diffraction angles dropped with increasing heat-treatment temperature. In addition, the initial modulus and tensile strength of the SDR-3.5 PBO fiber heat-treated at 550 °C (SDR-3.5 PBO 550 fiber) were found to be 19.1 GPa and 449.2 MPa, which were much higher than those of the SDR-3.5 PHA fiber, 9.3 GPa and 227.0 MPa, respectively.

Beyond Conventional Reaction Mechanism of Ordered Mesoporous Nickel Oxide for Lithium Ion Batteries

In a recent days, as cutting-edge devices, such as cell phone, electric vehicle (EV) and energy storage system (ESS) become more sophisticated, the battery performance is required to be higher. As a result, metal oxides having a capacity several times larger than that of carbon have attracted attention as a candidate for a next-generation secondary battery. Although metal oxides show higher capacity than one of conventional theory, which is insertion, alloy and conversion reaction, but it has not been clearly determined. Nickel oxide (NiO) is very attractive anode material due to its chemically stable, cheap, environmentally benign, easy to synthesize properties, and high theoretical capacity (718 mAh/g). However, commercialization of NiO is hampered by its poor cycle performance and rate capability due to inherently severe volume changes during cycling. One of strategies to overcome these limitations is to synthesize nanostructured NiO with various morphology, such as nanofibers, nanowalls, hollow spheres, hierarchical structures, and especially porous structure. In this study ordered mesoporous NiO is synthesized by using KIT-6 as a hard template for the sake of higher performance. Low-angle X-ray diffraction (XRD) patterns of highly ordered mesoporous NiO is quite different from KIT-6 silica template. A new (110) peak appears before 2θ=1°, which indicates the meso-structure transformation from cubic to tetragonal or the lower space group after the silica template etching process. In wide angle XRD pattern, synthesized highly ordered mesoporous NiO is matched with cubic NiO (JCPDS 47-1049). N2 adsorption-desorption isotherms show that the obtained replicas possess high specific surface areas (92 m2/g), and large pore volumes (0.24 cm3/g). The SEM images prove their mesoporous structures, indicating that nanoreplication was uniformly performed without formation of other metal oxide phase. Its theoretical capacity is calculated through conversion reaction, in which NiO reacts with Li ion and is converted to metallic Ni nanoparticles and Li2O, but the conventional reaction mechanism cannot elucidate its high reversible capacity (~1000 mAh/g). So synchrotron radiation analyses are used to research detail mechanism study. Conventional reaction mechanisms in anode, such as insertion, conversion, and alloy, have respective consistency as shown in operando SAXS. Operando SAXS spectra of mesoporous NiO shows different behavior during 1st discharge compared to one of other anode materials, which follow conversion reaction. There are no significant changes of SAXS until ~1 mol of Li ion is reacted. Thereafter, the pore net volume changes increase and peak intensity decrease gradually indicating the loss of mesostructure upon the conversion reaction to form Ni and Li2O. These observation is similar to in situ XRD, which shows constant peak intensity until ~1 mol of Li ion is reacted and decrease because of phase transition from ordered mesoporous structure to amorphous phase, result of conversion reaction. In these results, retained peak intensity might be attributed to electrolyte participation reaction, not associated with the NiO lattice. For further study, ex situ XAS analysis is used to study the local atomic structure of cycled NiO in detail. Ni K-edge XANES spectra show negligible changes in initial stage of 1st discharge. These changes are also clearly observed in Ni K-edge EXAFS spectra, which show pristine and discharged to 200 mAh/g samples are similar and peak intensity of discharged to 400 mAh/g sample is lower. It indicates that electrolyte participation reaction (oligomer layer formation) takes place first, and then the conversion reaction occurs. In the middle stage of 1st discharge, it goes to metallic Ni, product of conversion reaction. The amplitudes of Ni-O and Ni-Ni peaks in mesoporous NiO decrease significantly and the amplitudes of Ni-Ni peak in metallic Ni increase with the increase of depth of the discharge due to displacement of reacting species during conversion reaction. There are no significant changes due to SEI layer formation in final stage of 1st discharge. Note that little changes of Ni K-edge XANES spectra are observed until charged to 600 mAh/g sample, and it goes to NiO-like phase till fully charged state in the 1st charge. It indicates that reversible conversion reaction takes only some part of entire reversible capacity, and the reversible oligomer formation / decomposition attributes to the remained reversible capacity. A similar consistency is shown on 2nd discharge. The XPS and HRTEM experiments were carried out for research of the electrolyte participation reaction. More details will be discussed in the meeting.

Effect of Mutual Interaction between High and Low Stereo-Regularity Components on Structure Formation in Melt Spinning Process of Isotactic Polypropylene Blend Fibers

Abstract Fiber formation behavior of the blend fibers consisting of two types of isotactic polypropylene (iPP), i. e. high stereo-regularity/high molecular weight iPP (HPP) and low stereo-regularity/low molecular weight iPP (LPP), was investigated. In the melt spinning of blend fibers of various HPP:LPP compositions, the spinnability was improved significantly not only by blending LPP into HPP but also by blending HPP into LPP. On-line diameter measurement of the spin-line revealed that the increase of LPP composition caused the shift of solidification point to downstream, indicating that the crystallization temperature was lowered. Wide-angle X-ray diffraction (WAXD) analysis of the as-spun fibers clarified that only the α-form crystal was formed, and the crystalline orientation increased with the increases of take-up velocity and HPP weight fraction. The crystallinities obtained from the WAXD patterns of the as-spun fibers of various HPP/LPP compositions prepared at the take-up velocity of 1 and 5 km/min were lower than the values estimated based on the rule of additivity, where the difference was more prominent for the 1 km/min fibers. Analyses of crystallinity through differential scanning calorimetry measurements also suggested the suppression of the crystallization of HPP in the HPP/LPP blend fibers. The thermal analyses basically clarified that in the melt spinning process of the blends of HPP and LPP, both components crystallized independently even though the two polymers are considered to be miscible in the molten state, however, detailed analyses of melting behavior of the as-spun fibers suggested the possibility of the formation of crystals with a certain level of mixing of the HPP and LPP molecules, i. e. the mixing of a certain amount of LPP molecules into the HPP crystals and also the mixing of a certain amount of HPP molecules into the LPP crystals.

Structure and properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/poly(L-lactic acid) quasi core/sheath melt-electrospun microfibers

A facile route was proposed to fabricate core–sheath microfibers, and the relationships among processing parameters, crystalline structures and the mechanical properties were investigated. The compression molded poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)/poly(L-lactic acid) (PLLA) strip enhanced the spinnability of PHBH and the mechanical properties of PLLA as well. The core–sheath ratio of the fibers was determined by the prefab strip, while the PLLA sheath component did not completely cover the PHBH core component due to the weak interfacial tension between the melts of PHBH and PLLA. A rotational target was applied to collect aligned fibers, which were further drawn in a water bath. The tensile strength and the modulus of as-spun and drawn fibers increased with increasing the take-up velocities. When the take-up velocity was above 500 m/min, the jet became unstable and started to break up at the tip of the Taylor cone, decreasing the mechanical properties of the fibers. The drawing process facilitated the crystallization of PLLA and PHBH, and the tensile strength and the modulus increased linearly with the increasing the draw ratio. The crystal information displayed from wide-angle X-ray diffraction patterns and differential scanning calorimetry heating curves supported the results of the tensile tests.