Wide-angle X-ray Diffraction Spectra Research Articles

Dicationic pyridinium salts as new organic ionics: Changes in solid-state phases and thermal/electrochemical properties

To explore a new family of organic ionic materials, a series of α,ω-bis[N,N′-(4-alkylpyridinium)]alkane salts combined with iodide (I−), tetrafluoroborate (BF4−), and bis(trifluoromethanesulfonyl)imide (Tf2N−) anions and alkylene bridges of different lengths are synthesized. From 1H NMR chemical shift changes, the proton acidity of at the bis-pyridinium cations can be estimated for different anions. All the synthesized I− and BF4− salts have one or multiple solid–solid phase transitions, which are typical features of plastic and liquid crystals. The I− or BF4− salts with large values (>90 J mol−1 K−1) of total entropy changes in solid–solid phase transitions (Σ(ΔSss)) would have a very soft crystalline phase. Combined with polarized microscope images and wide-angle X-ray diffraction spectra, 1,2-bis[N,N′-(4-n-dodecylpyridinium)]ethane 2BF4– may be a true plastic crystal at temperatures above 70 °C. The thermal properties of the bis-pyridinium Tf2N− salts are quite different; they show only a melting transition and are thermally more stable than those of I− and BF4−. The electrochemical window of the bis-pyridinium BF4– and Tf2N− salts is stable up to 4.3 V (vs. Li/Li+).

Low Dielectric Poly(imide siloxane) Films Enabled by a Well-Defined Disiloxane-Linked Alkyl Diamine.

This paper presents an efficient pathway to achieve the dielectric constant as low as 2.48 @ 25 °C, 1 MHz for nonporous poly(imide siloxane) films with mechanical and thermal robustness. A symmetric disiloxane-linked alkyl diamine, bis(aminopropyl)tetramethyldisiloxane (BATMS) with a well-defined molecular formula NH2CH2CH2CH2Si(CH3)2OSi(CH3)2CH2CH2CH2NH2, has been used to controllably reduce the dielectric constant of the polymer films by adjusting the loading of BATMS. The thermal stability of all the polymer films remains robust with T5 and T10 no less than 458 and 472 °C, respectively, while the glass-transition temperature decreases with increasing incorporation of flexible disiloxane-alkyl segments into a polymer backbone. There exists a consistent regularity between the thermal, optical, and dielectric properties with the loading amount of BATMS in the polymer films, inferring that the disiloxane-alkyl segments are homogeneously distributed in the polymer backbone. Charge-transfer complex inhibition of polymer films by disiloxane segments has been revealed by an enlarged d-spacing in wide-angle X-ray diffraction spectra and a blue shift in film fluorescence emission spectra. The combined low dielectric constant, robust mechanical and thermal stability, and improved hydrophobicity make the series of BATMS-resulting poly(imide siloxane) films promising candidates for sophisticated flexible microelectronic application.

Effect of Hollow Glass Microspheres on the Morphology, Rheology and Crystallinity of Short Bamboo Fiber-Reinforced Hybrid Polypropylene Composite

Light-weight and high-strength polymer composites have attracted the special attention of automotive and aerospace sectors since they offer advantages such as less fuel consumption and higher fuel efficiency. In the present study, an effort has been made to prepare such polymer composites using natural fiber and very low-density hollow inorganic particles. The use of hollow glass microspheres (HGM) as a potential filler particle for making light-weight hybrid polymer composites was investigated. Polypropylene (PP) and maleic anhydride-grafted-polypropylene (in 9:1 ratio) constituted the base matrix (BM). For strength reinforcement, alkali-treated short bamboo fibers (SBF) were employed, while for making the composite material light in weight, HGM were incorporated. Silane treatment of HGM by (3-aminopropyl)triethoxysilane was performed to enhance interfacial adhesion with BM. Adequate wetting of HGM and SBF was evident from the SEM images of cryo-fractured samples. A 14% increase in tensile strength was observed in comparison to virgin PP for the composite with 5 wt.% HGM, and a desirable decrease in density was observed for all the composite samples with increasing HGM content. Improvement in hardness but a marginal decrease in impact strength due to HGM fillers was observed. Rheological analysis of the composite melt samples showed an apparent increase in the complex modulus with increasing HGM content. Thermal analysis of the composites revealed a significant impact of hybrid fillers on the crystallinity, with SBF showing a minimal effect while HGM reducing it significantly. Wide-angle x-ray diffraction spectra showed changes in the crystal structure of the composite with noticeable β-form peaks.

High-performance polyimide copolymer fibers derived from 5-anino-2-(2-hydroxy-4-aminobenzene)-benzoxazole: Preparation, structure and properties

A series of high-performance polyimide copolymer (co-PI) fibers containing phenylenebenzoxazole moiety with one hydroxyl group are synthesized based on the copolymerization of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) with two diamine monomers, namely, p-phenylenediamine (p-PDA) and 5-anino-2-(2-hydroxy-4-aminobenzene)-benzoxazole (p-mHBOA), through a two-step method. The molar ratio of p-PDA/p-mHBOA varies from 10/0 to 0/10. Influences of the p-mHBOA moieties on the thermal stability, crystal structure, crystal orientation, microvoid morphology, and mechanical properties are systemically investigated. Fourier transform infrared results confirm that intra/inter molecular hydrogen bonds come from the OH group and nitrogen atom of the benzoxazole group and/or OH group and the oxygen atom of the carbonyl group of cyclic imide. The glass transition temperatures (Tgs) of co-PI fibers are in the range of 290 °C–325 °C. The prepared fibers show excellent thermal stabilities, and their T5% is within 528 °C–542 °C in air. Two-dimensional wide-angle X-ray diffraction spectra indicate that homo-PI and co-PI fibers present a regularly arranged polymer chains along the fiber axial direction. Moreover, the ordered molecular packing along the transversal direction of fibers is destroyed by the copolymerization. Small-angle X-ray scattering results show that co-PI fibers with optimal mechanical properties exhibit the shortest average length (L) and the smallest radius (R¯) of microvoids. When the p-mHBOA/p-PDA molar ratio is 5/5, the fracture strength and initial modulus can reach approximately 30.31 cN/dtex (4.40 GPa) and 894.88 cN/dtex (129.8 GPa), respectively. The relationship between structure and mechanical properties is also discussed.

Nanostructured mesoporous silica: influence of the preparation conditions on the physical-surface properties for efficient organic dye uptake.

A series of ordered mesoporous silica such as MCM-41, SBA-3 and SBA-15, in addition to silica micro- (SM) and nano- (SN) mesoporous particles, were prepared. The preparation conditions were found to greatly influence the physical-surface properties including morphological structure, porosity, particle size, aggregate average size, surface area, pore size, pore volume and zeta potential of the prepared silica, while the chemical structure, predicted from FT-IR spectra, and the diffraction patterns, predicted from wide-angle X-ray diffraction spectra, were identical. Surface areas of approximately 1500, 1027, 600, 552 and 317 m2 g−1, pore volumes of 0.93, 0.56, 0.82, 0.72 and 0.5 cm3 g−1, radii of 2.48, 2.2, 5.66, 6.6 and 8.98 nm, average aggregate sizes of 56, 65.4, 220.9, 73, 61.1 and 261 nm and zeta potential values of −32.8, −46.1, −26.3, −31.4 and −25.9 mV were obtained for MCM-41, SBA-3, SBA-15, SN and SM, respectively. Methylene blue dye uptake capacity of the prepared silica types was investigated using the batch technique and, in addition, the most effective material was further studied by the column flow system. The kinetics and isotherms of the uptake process were studied. The morphological structure, surface area, pore radius and zeta potential values were the most correlated factors.

High-performance polyimide fibers derived from wholly rigid-rod monomers

Insufficient mechanical properties are one of the major obstacles for the wide application of polyimide (PI) fibers, especially utilized as reinforcement in structural composites. In this work, the copolymerization of two rigid-rod diamines, 2,5-bis(4-aminophenyl)-pyrimidine (PRM) and p-phenylenediamine (PPD), with the 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) was developed to fabricate PI fibers with high strength and high modulus. The effects of chemical structure (diamine molar ratio) on the molecular packing behavior, micromorphology as well as properties of the resulting co-PI fibers have been investigated in detail. Wide-angle X-ray diffraction spectra showed that co-PI fibers exhibited higher oriented structures with lower lateral packing order degrees in relative to both homo-BPDA/PRM and homo-BPDA/PPD PI fibers, and the Hermans’ orientation degrees reached 0.97 for the two samples with PRM/PPD molar ratio of 5/5 and 4/6. Small-angle X-ray scattering (2D SAXS) patterns indicated that the co-PI fiber with the PRM molar content of 50% showed the densest inner structure. Accordingly, this co-PI fiber presented a higher mechanical performance (tensile strength of 3.11 GPa and modulus of 144.2 GPa) as compared to those PI fibers reported previously. Meanwhile, these wholly rigid-rod PI fibers exhibited excellent thermal stabilities with the 5 and 10% weight loss temperatures ranging from 548 to 565 °C and from 572 to 589 °C, respectively. The prominent comprehensive properties make these PI fibers strong candidates for the future fiber-reinforced polymer composites.

Fabrication and characterization of co-polyimide fibers containing pyrimidine units

A series of co-polyimides (co-PIs) containing pyrimidine rings were synthesized by reacting the self-synthesized diamine 2,5-bis(4-aminophenyl)-pyrimidine (PRM) with commercial 4,4’-diaminodiphenyl ether (ODA) and aromatic 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). A series of co-PI fibers were produced using a two-step wet-spinning method, including extrusion, coagulation, washing, drying, thermal imidization and hot-drawing processes. Orientation structures of the precursor co-PAA fibers formed in the wet-spinning process, and their effects on the thermomechanical properties of the as-spun co-PI fibers were discussed. An interesting phenomenon has been found that glass transition temperatures (T gs) of as-spun co-PI fibers decreased with increasing orientation factors, which was explained based on some previous works. Two-dimensional wide-angle X-ray diffraction spectra of the final co-PI fibers showed that samples with higher PRM contents show highly oriented and well-ordered crystalline structures, which account for the enhanced mechanical properties when incorporating PRM moieties. The co-PI fiber with the PRM/ODA molar ratio of 6/4 showed an optimum tensile strength and modulus of 3.1 and 90 GPa, respectively, showing a great potential in light advanced composites.

Insight into the multiscale structure of pre-stretched recast Nafion® membranes: Focus on the crystallinity features

The structure of solution cast Nafion® membranes that were uniaxially stretched, and then thermally annealed was studied over an extended observation window, from a few angstroms to several hundreds of angstroms, using both Small-Angle X-Ray Scattering (SAXS) and Wide-Angle X-Ray Diffraction (WAXD). This Nafion® membrane preparation allowed highlighting new structural features, never reported previously. Indeed, while SAXS data evidenced moderate effect of stretching with different behaviors of the matrix and ionomer peaks, WAXD spectra showed a strong stretching induced anisotropy of the crystalline phase. These results defy the Nafion® structural models and call for further theoretical and experimental developments taking into account these new data.

Structure and properties of polyimide fibers containing benzimidazole and Amide Units

ABSTRACTCo‐polyimide (co‐PI) fibers with outstanding mechanical properties were fabricated via thermal imidization of polyamic acids, derived from a new design of combining the amide and benzimidazole diamine monomers, 4‐amino‐N‐(4‐aminophenyl)benzamide (DABA) and 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (BIA), with 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA). The crystalline structure and micromorphology of the prepared co‐PI fibers were investigated by synchrotron wide‐angle X‐ray diffraction (WAXD) and small‐angle X‐ray scattering (SAXS). The two‐dimensional WAXD spectra imply that the co‐PI fibers possess a structure between smectic‐like and three‐dimensionally ordered crystalline phase, and all the obtained fibers are highly oriented along the fiber axis. SAXS patterns exhibit a pair of meridional scattering streaks for the homo‐PI (BPDA/BIA) fiber, suggesting the presence of periodic lamellar structure. The incorporation of DABA into the polymer chains destroyed the lamellar structure but led to smaller size of microvoids upon increasing DABA moiety, based on SAXS analysis. The co‐PI fibers, with the molar ratio of BIA/DABA being 7/3, exhibited the optimum tensile strength and modulus of 1.96 and 108.3 GPa, respectively, attributed to the well‐defined ordered and dense structure. The chemical structure and molecular packing significantly affected the thermal stability of fibers, resulting in the different glass transition temperatures (Tg) from 350 to 380 °C. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 183–191

Mechanism of increasing the reducing sugar yield in cellulose hydrolysis via modification with 2,4-dianilino-6-chloro-s-triazine

Cellulose, one of the most abundant and useful natural resources from products of forests, has become increasingly important because of its conversion to bio-ethanol. Yet, the low yield of the conversion is the key problem that should be solved. Microcrystalline cellulose was chemically modified with 2,4-dianilino-6-chloro-1,3,5-triazine to increase the yield of hydrolysis of cellulose for high glucose generation. The modifier, 2,4-dianilino-6-chloro-1,3,5-triazine, was synthesized from 2,4,6-trichlorine-1,3,5-triazine and aniline, and the chemical structure of the modifier was determined by Fourier transform-infrared, nuclear magnetic resonance and mass spectrometry techniques. The structure of the modified microcrystalline cellulose was characterized by Fourier transform-infrared spectrometry and wide-angle X-ray diffraction techniques. The hydrolysis of the modified microcrystalline cellulose had been studied and the yield of the reducing sugar reached the highest when the relative molar percentage of 2,4-dianilino-6-chloro-1,3,5-triazine to the cellulose (based on the remained glucose unit) was about 30 %. The change of the crystalline structure of cellulose by chemical modification, which was suggested by wide-angle X-ray diffraction spectra, was propitious to the hydrolysis of cellulose. Furthermore, the yield of hydrolysis varied with the loading of the modifier which was due to the change of the crystalline structure of the modified cellulose. It might be a probable mechanism of yield improvement via modification that was verified by the calculated result of crystalline index and crystallite size.

Miscibility Study of Chitosan and Methylcellulose Blends

The miscibility of chitosan / methylcellulose (CH/MC) blends was studied by FT IR, wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), and scanning electronic microscopy (SEM). The regular changes of FT IR and WAXD spectra of CH/MC blend powder indicated the miscibility of the blends. TGA curves and SEM images of cross-sections of the blends films showed partly miscibility.

Development of poly(amidoamine) dendrimer/poly(vinyl alcohol) hybrid membranes for CO2separation

Abstract A novel hybrid membrane of poly(amidoamine) (PAMAM) dendrimer/cross-linked poly(vinyl alcohol) (PVA) was developed for the selective separation of CO2 from a mixture of CO2 and H2. PAMAM dendrimers were incorporated into a cross-linked PVA matrix to improve CO2 separation performance at elevated pressures. An organic metal compound di-isopropoxy-bis(triethanol aminato) titanium (Ti cross-linker) was selected as the PVA cross-linker. The characterization of PAMAM/cross-linked PVA hybrid membranes was conducted using Fourier transform infrared spectrometry/attenuated total reflectance (FTIR/ATR), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS) spectra. Cross-linking of PVA with Ti cross-linker was confirmed by FTIR/ATR spectra. WAXD spectra showed that the relative crystallinity of PAMAM/PVA hybrid membrane decreased greatly when compared with PVA film. SAXS results indicated that PAMAM and PVA are compatible in the PAMAM/PVA hybrid membrane. To improve the CO2 separati...

Synthesis of Mixed Ceramic MgxZn1–xO Nanofibers via Mg2+ Doping Using Sol–Gel Electrospinning

We report on the synthesis of tuned energy band gap Mg(x)Zn(1-x)O nanofibers (NFs) with different Mg(2+) content via the sol-gel electrospinning (ES) technique wherein the addition of the doping material affects not only the morphologies of as-spun ZnAc/PVA and MgAc/ZnAc/PVA nanofibers but also the crystal microstructure and optical properties of calcined ZnO and Mg(x)Zn(1-x)O nanofibers. Following an appropriate aqueous solution preparation of magnesium acetate (MgAc) and zinc acetate (ZnAc) with poly(vinyl alcohol) (PVA), electrospinning is performed and then as-spun nanofibers are calcined in an air atmosphere at 600 °C for 3 h. As-spun and calcined nanofiber diameters and morphologies are evaluated with scanning (SEM) and transmission (TEM) electron microscopies, whereas crystalline microstructural interpretations of ZnO and Mg(x)Zn(1-x)O are conducted with wide-angle X-ray diffraction spectra (XRD). Surface chemical composition and elemental evaluation of calcined nanofibers are examined with X-ray photoelectron spectroscopy (XPS), and optical properties and crystal defect analyses of the calcined nanofibers are conducted with photoluminescence spectra (PL). We observe a sharp reduction in fiber diameter upon calcination as a result of the removal of organic species from the fibers and conversion of ceramic precursors into ceramic nanofibers, and the appearance of a range of fiber morphologies from "bead in a string" to "sesame seed" coverage depending on fiber composition. Because Zn(2+) and Mg(2+) have similar ionicity and atomic radii, some Zn(2+) atoms are replaced by Mg(2+) atoms in the crystals, leading to a change in the properties of crystal lattices. The band gap energy of the calcined fibers increases significantly with addition of Mg(2+) along with an increase in the ultraviolet (UV) photoluminescence emission of the fibers.

Synthesis and properties of novel alicyclic-functionalized polyimides prepared from natural-(D)-camphor

In this article, a new alicyclic-functionalized diamine, 1,3-bis(4-aminophenoxymethylene)-1,2,2-trimethylclopentane (BAMT) was successfully synthesized starting from natural —(D)-camphor through four reaction steps of oxidation to offer a dicaboxylic acid, reduction to offer a diol, nucleophilic substitution to give a dinitro compound and then reduction to give the final diamine. Two alicyclic-containing polyimides were prepared by polycondensing BAMT with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-oxydiphthalicanhydride (ODPA), respectively. For the studies of the structure–property relationships of the polyimides, one aromatic polyimide of 4, 4′-oxydianiline (ODA) polycondensed with ODPA was prepared in comparison. The alicyclic-containinig polyimides PI (BPDA-BAMT) and PI (ODPA-BAMT) maintain good thermal properties with glass transition temperatures (Tg) of 257°C and 240°C, and temperatures at 5% weight loss (T5) of 443°C and 436°C in nitrogen, respectively. The alicyclic polyimides exhibit tensile strengths of 91.9–133 MPa, Young's moduli of 2.75—3.24 GPa, and elongations at break of 5.6–18%. Compared with the aromatic polyimide PI (ODPA-ODA), PI (ODPA-BAMT) shows improved transparency with the UV-Vis transmittance at 500 nm over 80%. In addition, PI (ODPA-BAMT) displays better solubility than PI (ODPA-ODA), which has been confirmed by the bigger d-spacing value of PI (ODPA-BAMT) than that of PI (ODPA-ODA) calculated from the Wide-angle X-ray Diffraction spectra. This study indicates that the renewable forestry compound, such as natural —(D)-camphor, could be a good origin for the structural designing and preparation of alicyclic-containing polyimides with outstanding combined features suitable for advanced microelectronic and optoelectronic applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

SAXS/DSC/WAXD study of TiO2 nanoparticles and the effect of γ-radiation on nanopolymer electrolyte

Nanostructured polymer electrolytes are very attractive materials for components of batteries and opto-electronic devices. (PEO)8ZnCl2 polymer electrolytes and nanocomposites were prepared using Poly(ethylene oxide) (PEO) γ-irradiated with a selected dose of 529 kGy and with an addition of 10% of TiO2 nanograins. The influence of the added nanosize TiO2 grains on the polymer electrolytes and the effect of the γ-radiation from a Co-60 source were studied by small-angle X-ray scattering (SAXS) simultaneously recorded with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) at the synchrotron ELETTRA. Infrared (IR) and impedance spectroscopy (IS) were also performed [1]. It was shown by previously performed IS that the room temperature conductivity of the nanocomposite polymer electrolyte increased more than two times above 65 °C, relative to pure composites of PEO and salts. We observed all changes between 20 °C and 100 °C for treated and as prepared polymer electrolyte in the SAXS, DSC and WAXD spectra and especially during the phase transition to the super-ionic phase at 65 °C [2,3]. The SAXS/DSC measurements yielded insight into the temperature-dependent changes of the grains of the electrolyte as well as into the differences due to different heating and cooling rates. The crystal structure and the melting and crystallization temperatures of the nanosize grains were revealed by the simultaneous WAXD measurements.

Miscibility and Liquid Crystallinity Studies of Chitosan/Ethylcellulose Blends

The miscibility of chitosan/ethylcellulose (CH/EC) blends was studied by FT IR, wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electronic microscopy (SEM). The regular changes of FT IR and WAXD spectra of CH/EC blend powder indicated the miscibility of the blends. DSC curves and SEM images of cross-sections of the blends films showed partly miscibility. CH/EC blends could form anisotropic phase in their formic acid solutions observed on a polarizing light microscope (PLM).

Self‐Assembly of Chiral trans‐Cyclobutane‐Containing β‐Dipeptides into Ordered Aggregates

Two chiral synthetic β-dipeptides have been constructed, one with two trans-cyclobutane residues and the other with one trans and one cis fragment, 1 and 2, respectively, and investigated to get insight into the non-covalent interactions responsible for their self-assembly to form ordered aggregates, as well into parameters such as their morphology and size. Experimental evidence of the formation of these assemblies was provided by spectroscopy, microscopy and X-ray diffraction experiments that suggest the formation of nanoscale helical aggregates. This process involves a conformational change in the molecules of each dipeptide with respect to the preferred conformation of the isolated molecules in solution. A high-resolution NMR spectroscopy study allowed the determination of the dynamics of the gelation process in [D(8)]toluene and the sol-gel transition temperature, which was around 270 K in this solvent at a concentration of 15 mM. NMR spectroscopy experiments also provided some information about conformational changes involved in the sol-gel transition and also suggested a different gel packing for each dipeptide. These observations have been nicely explained by computational studies. The self-assembly of the molecules has been modelled and suggested a head-to-head molecular arrangement for 1 and a head-to-tail arrangement for 2 to give helical structures corresponding to hydrogen-bonded single chains. These chains interact with one another in an antiparallel way to afford bundles, the significant geometry parameters of which fit well to the main peaks observed in wide-angle X-ray diffraction spectra of the aggregates in the solid state.

Nitration and amination of polyphenylene oxide: Synthesis, gas sorption and permeation analysis

A high degree of nitration of polyphenylene oxide (PPO) was successfully achieved by carefully optimizing synthetic protocol. The reduction of nitro group to amino could be done quantitatively. The physical properties of formed polymers were investigated and correlated with gas sorption and permeation properties. The formed polymers were amorphous in nature as revealed by wide angle X-ray diffraction spectra. An increase in the packing density in comparison to unsubstituted PPO as a result of induced polarity was indicated by lowering of fractional free volume and d-spacing. The substitution by either nitro or amino group increased the chain stiffness as revealed by the dynamic mechanical analysis. Though both, nitro and amino group substitution on PPO led to a decrease in pure gas permeability, the selectivity of various gas pairs was increased by these substitutions. The gas sorption analysis revealed that both, solubility selectivity and diffusivity selectivity were increased by these polar group substitutions. The nitro group substitution was more effective in improving solubility selectivity, while amino group substitution was more effective in improving diffusivity selectivity.

Some observations on the high-resolution solid-state CP-MAS 13C-NMR spectra of periodate-oxidised cellulose

Oxidation of cellulose by sodium metaperiodate leads to a decrease in the crystallinity. A wide-angle X-ray diffraction (WAXRD) study of oxidised celluloses [2,3-dialdehyde celluloses (DAC), 2,3-dicarboxycelluloses (DCC) and sodium 2,3-dicarboxylate celluloses (NaDCC)] showed that the crystalline peak at 2Θ = 22.7 ° decreased almost proportionately with the degree of oxidation of the starting cellulose. In the WAXRD spectra, no new crystalline peaks were observed for the oxidised celluloses, further indicating their amorphous nature. High-resolution, solid-state, cross-polarisation-magic angle spinning (CP-MAS) 13C nuclear magnetic resonance (NMR) spectra of these same oxidised cellulose samples were recorded in order to investigate the changes occurring with increasing oxidation levels. For each series of spectra of increasing oxidation levels of DAC, DCC and NaDCC an increasing trend towards the formation of a multiplicity of peaks was observed, owing to the numerous stereochemical configurations and rotameric conformations possible. The 98% oxidised cellulose samples represent almost pure compounds (new, linear, cellulose-derived polymers). The spectra and observed chemical shifts for this series are being reported for the first time in this paper. It is shown that solid-state NMR can be useful in investigations of oxidatively degraded celluloses.

A X-ray line profile study on as-polymerized isotactic polypropylene

The line profile analysis of high-resolution wide angle X-ray diffraction spectra (WAXS) has been employed to characterize two polypropylenes polymerized by: a) “conventional” Ziegler-Natta catalyst (PP-A) and b) “high-yield” new supported catalyst (PP-B). The observed differences in line-width are most reasonably due to a marked crystallite size anisotropy, more pronounced for PP-A. The smallest size is along the crystallographic a-axis, which is the preferred direction of growth of crystallites. Paracrystalline fluctuations, on the whole larger in the high-yield polymer than in the conventional one, are present. The diffuse background resulting from line profile analysis is preliminarily investigated here in terms of scattering from a microcrystalline array.