Wide-angle X-ray Diffraction Methods Research Articles

Crystalline structure of cellulose in wood after chemical modification using cyclic acid anhydrides (maleic and succinic)

The chemical modification of wood can be directed to improve various properties, e.g., the dimensional stability, hardness properties, and/or durability properties, against weathering. In this study, a Romanian softwood species Abies alba Mill. was treated and chemically modified using two cyclic acid anhydrides, i.e., maleic and succinic, to improve its interfacial properties relative to unmodified wood. Structural changes, with focus on the evolution of crystalline part in wood after chemical modification, the water absorption, and the water repellent efficiency, were determined. Maleic anhydride exhibited a lower reactivity towards wood substrate than succinic anhydride, presumably because of their different chemical structure (maleic anhydride is very sensitive to the presence of water). It was found that the percentage of water absorption was diminished, primarily after the succinic anhydride treatment. The chemically modified wood was characterized via Fourier transform-infrared spectroscopy and wide-angle X-ray diffraction methods. The crystalline part from wood structure was evidenced in relation to the employed anhydride in chemical modification approach.

Synthesis, Characterization and Dynamic Mechanical Properties of Polyimide-Polyurea-Polysilsesquioxane Block Terpolymers

A novel type of polyurea-b-polyimide(PUI)-LPS terpolymer containing ladder like polysilsesquioxane (LPS) hybrid thin film was successfully prepared by coupling ladder-like polysilsesquioxane (LPS) with polyurea-b-poly(amide acid), followed solution film casting and thermal imidization. The LPS composed of mercapto and fluoride side groups was synthesized by sol–gel and monomer self-assembly methods. The structure and properties of the resulting PUI-LPS thin films were affected by the reaction conditions. Dynamic contact angles (DCA) and dynamic mechanical analysis (DMA) were used to study the surface energy and mechanical properties of PUI-LPS thin films. The presence of LPS containing fluoride and mercapto side groups significantly increased the extent of cyclodehydration (imidization) process at a relatively low temperature of about 150°C. The surface energy of the hybrid thin films was remarkably decreased as LPS concentration increased. The dynamic mechanical properties of the hybrid thin films were determined by dynamic mechanical analysis (DMA). Fourier transform infrared spectroscopy (FTIR) and Wide-angle X-ray diffraction (WAXRD) methods were used to study the composition and structure of the hybrid thin films

Preparation of Smart Surfaces Based on PNaSS@PEDOT Microspheres: Testing of E. coli Detection.

The main task of the research is to acquire fundamental knowledge about the effect of polymer structure on the physicochemical properties of films. A novel meta-material that can be used in manufacturing sensor layers was developed as a model. At the first stage, poly(sodium 4-styrenesulfonate) (PNaSS) cross-linked microspheres are synthesized (which are based on strong polyelectrolytes containing sulfo groups in each monomer unit), and at the second stage, PNaSS@PEDOT microspheres are formed. The poly(3,4-ethylenedioxythiophene) (PEDOT) shell was obtained by the acid-assisted self-polymerization of the monomer; this process is biologically safe and thus suitable for biomedical applications. The suitability of electrochemical impedance spectroscopy for E. coli detection was tested; it was revealed that the attached bacterial wall was destroyed upon application of constant oxidation potential (higher than 0.5 V), which makes the PNaSS@PEDOT microsphere particles promising materials for the development of antifouling coatings. Furthermore, under open-circuit conditions, the walls of E. coli bacteria were not destroyed, which opens up the possibility of employing such meta-materials as sensor films. Scanning electron microscopy, X-ray photoelectron spectroscopy, water contact angle, and wide-angle X-ray diffraction methods were applied in order to characterize the PNaSS@PEDOT films.

Nitro-oxidized carboxycellulose nanofibers from moringa plant: effective bioadsorbent for mercury removal

Mercury contamination in drinking water is a worldwide problem due to its severely harming effects on the human body. A nanostructured natural bioadsorbent, carboxycellulose nanofiber extracted from raw moringa plant using the nitro-oxidation method (termed NOCNF), capable of effectively remediating this problem has been demonstrated. Nitro-oxidation is a simple approach that can extract carboxylated nanocellulose directly from raw biomass. In this study, the produced NOCNF contained a large density of carboxylate groups on the cellulose surface (0.97 mmol/g), capable of removing Hg2+ ions by simultaneous electrostatic-interactions and mineralization processes. Using the Langmuir analysis, the adsorption results indicated that the highest Hg2+ removal capacity of this NOCNF was 257.07 mg/g, which is higher than most of the reported values. The interactions between Hg2+ and NOCNF were further characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy with electron diffraction and wide-angle X-ray diffraction methods, suggesting the existence of two distinct removal mechanisms: predominant adsorption at low Hg2+concentrations (< 250 ppm) and predominant mineralization at high Hg2+ concentrations (> 1000 ppm). The applications of NOCNF were illustrated in both suspension form, as an adsorbent/coagulant, and dry powder form using filtration column. The results indicated that NOCNF in suspension exhibited a higher maximum removal efficiency of 81.6% as compared to the dry state of 74.3%. This work demonstrated the feasibility of extracting nanostructured adsorbents from biomass feedstocks to tackle the Hg2+ contamination problem in drinking water.Graphic abstractCellulose nanofibers, extracted from Moringa plant using the nitro-oxidation method, exhibit excellent adsorption capacity for Mercury (II) removal.

Poly(L-glutamic acid) via catalytical hydrogenation for the fabrication of carbon nanotube nanocomposites

Abstract The synthesis of poly(L-glutamic acid) (PG) was investigated. Reduction of poly(benzyl-L-glutamate) by the palladium/charcoal catalyst proved to be an effective method for obtaining polyglutamic acid pure and particularly exhibiting in the α-helix secondary structure. The structure of this synthetic polypeptide was assessed by infrared spectroscopy, gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, temperature-modulated differential scanning calorimetry and wide-angle powder X-ray diffraction methods. The α-helical PG was, for the first time, combined with multi-walled carbon nanotubes (MWCNTs). The obtained PG was demonstrated to be a promising matrix to disperse MWCNTs, forming MWCNT/PG biocomposites.

Solvent gradient fractionation of Polybutene-1 resin and its molecular weight dependency of Form II to I transformation

The influence of the molecular weight on the crystallization and crystalline phase transformation in polymorphic polybutene-1 (PB-1) is a controversial issue in literature. We suppose the main reason comes from the used commercial samples with broad molecular weight distribution (MWD). To overcome this, one homo-polymer PB-1 resin is effectively separated by solvent gradient fractionation (SGF) according to molecular weight to obtain fractions with narrow MWD for the first time. The appropriate solvent system is selected, i.e. the good solvent and poor solvent are 1,2,4-trimethylbenzene (TMB) and n-butyl cellosolve (BCS), respectively. Most of fractions have narrow polydispersity index less than 1.4. The molecular weights of SGF fractions gradually increase from 3.19 × 104 g/mol to 1.21 × 106 g/mol when the content of good solvent increases in the mixed solvent. In addition, the influence of the molecular weight on the transformation from Form II to Form I at 25 °C is investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) methods. It is found that the higher molecular weight is beneficial to the transformation in the initial stage (0–8h) and the lower molecular weight is beneficial to the transformation in the late stage (over 72h), i.e. the molecular weight has a double influence on the transformation rate from Form II to Form I. And the reasons are also discussed. Our results clarify the influence of molecular weight on transformation from Form II to Form I for PB-1 resin at 25 °C.

The influence of stabilization efficiency on skin–core structure and properties of polyacrylonitrile fibers

In this paper, we report the efficient preparation of polyacrylonitrile-based carbon fibers (CFs) by increasing the stabilization temperature and shortening the stabilization time. The oxidized fibers (OFs) were firstly prepared from precursor fibers (PFs) with different diameters at high stabilization efficiency. The skin–core structure of the obtained OFs was studied by optical microscopy, scanning electron microscopy, atomic force microscopy and nanoscale infrared laser spectroscopy, which revealed that fine denier PFs were more suitable for high-efficient stabilization treatment. Moreover, fine denier PFs were stabilized using four different temperature profiles, and then carbonized under stationary processing conditions to fabricate CFs with different stabilization efficiencies. The skin–core structure, crystallite thickness and mechanical properties of the obtained CFs were tested by scanning electron microscopy, Raman spectra, wide-angle X-ray diffraction and tensile testing methods. Noteworthily, T400-grade CFs were achieved and the manufacturing time was reduced by increasing stabilization efficiency, thus lowering the production costs of CFs.

The resistance of poly-(l-lactide) to gamma radiation: effect of initial preparation and crystallinity

In order to investigate the resistance of poly-(l-lactide) (PLLA) to high-energy radiation, two varieties of samples with substantial differences in microstructure and crystallinity are prepared and exposed to the gamma radiation to various absorbed doses (up to 300 kGy). Since the PLLA morphology is sensitive to preparation conditions and radiation, surface microstructures are analyzed by scanning electronic microscopy. The chain scission degradation is followed using a gel permeation chromatography, while the additional characterization is conducted by differential scanning calorimetry, wide-angle X-ray diffraction method and IR spectroscopy. Presented results show that the quenched samples are more susceptible to radiation than initially high crystalline ones. Furthermore, the radiation leads to two considerably dissimilar recrystallization dynamics, connected with initial structural differences and the presence/absence of taut-tie chains. Radiation-induced increase in the crystallinity (more than 25% of initial value) for the quenched samples is noticeable at low radiation doses.

Phase Transition from Tetragonal Form II to Hexagonal Form I of Butene-1/4-Methyl-1-pentene Random Copolymers: Molecular Factor versus Stretching Stimuli

The phase transition from the kinetically favored tetragonal form II into the thermodynamically stable hexagonal form I is the general phenomenon and core issue in application of polybutene-1-based materials. It is known that the variation of molecular structure by copolymerizing counits and the imposition of external stretching both greatly affect the phase transition. In this work, a series of butene-1/4-methyl-1-pentene (4M1P) random copolymers were synthesized with the dimethylpyridylamidohafnium/organoboron catalyst, where the 4M1P incorporated is the counit type of depressing II–I phase transition. Mechanical tests were combined with the in-situ wide-angle X-ray diffraction (WAXD) method to study the competing effects of the presence of 4M1P counits and stretching on the II–I phase transition. First of all, the quiescent experiments reveal that addition of 4M1P counits not only slows down transition kinetics but also decreases the ultimate form I fraction in the transition plateau. The 4M1P concentr...

Structure and Properties of the Welded Joints of Single-Type Polyethylenes Formed Under the Action of Constant Magnetic Fields

We study the structural features and the thermomechanical and operating properties of the welded joints of PE-80–PE-80 with PE-100–PE-100 made with and without the action of constant magnetic fields (B ~ 1 T). By using the wide-angle X-ray diffraction method, it is shown that the action of a transverse constant magnetic field on the melts of polyethylene specimens of the same type in the course of their welding causes the formation of an oriented structure of the welded joint. The axis of its texture coincides with the direction of the magnetic field, which improves the thermomechanical and operating properties of welded joints. The formation of a welded joint under the action of a longitudinal magnetic field leads to the deterioration of its physicomechanical characteristics, which is explained by the opposing action of the force field that formed in the process of welding and compensating the effect of the magnetic field.

Chitosan-based membranes with different ionic crosslinking density for pharmaceutical and industrial applications

Chitosan membranes (Ch), ionically crosslinked with pentasodium tripolyphosphate (TPP), were prepared using chitosan of medium and high molecular weight of similar degree of deacetylation and different crosslinking conditions. An effect of synthesis conditions (pH of crosslinking TPP solution equal to 5.5 and 9.0) on molecular and supermolecular structure and on crosslinking density of Ch/TPP membranes was confirmed using Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD) method and energy dispersive X-ray (EDX) spectrometry. Atomic-force microscopy (AFM) and contact angle measurements indicated some differences in membrane roughness and hydrophilicity. The state of water in non-crosslinked and ionically crosslinked Ch membranes containing different amount of water was investigated by low temperature differential scanning calorimetry (DSC) measurements. DSC analysis confirmed presence of freezing and non-freezing water in non-crosslinked and ionically crosslinked membranes. The amount of non-freezing water generally decreased after Ch crosslinking and was affected by crosslinking conditions and crosslinking density. Molecular weight of Ch had only slight influence on all characterized properties of ionically crosslinked membranes.

Effect of enantiomeric monomeric unit ratio on thermal and mechanical properties of poly(lactide)

The monomer of poly(lactide), i.e. lactic acid is an optically active compound and thus renders optical activity in the polymer itself. In the present studies highly crystalline and low crystalline grades of poly(lactide) were used to prepare blends with different d- and l-ratios to explore the relation between d- and l-content and various properties of poly(lactide). Optical rotation was measured by Polarimetry to analyse d-content in the blends which was found to vary from 0.05 to 4.14 %. Polarized light microscopy revealed that both the growth rate and final average size of the spherulites increased with the decrease of d-content. The crystallinity was measured by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) methods. It was noticed that a small change in d-content produced remarkable changes in crystallinity and other properties of the blends. The mechanical properties were slightly modified with the decrease in d-content.

Crystallization of Polylactic Acid Composites with Banana and Hemp Fibres by Means of DSC and XRD Methods

This paper deals with the evaluation of crystalline structure and thermal properties of injection molded parts based on polylactic acid (PLA) matrix reinforced by banana and hemp natural fibres (NF). Using differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) methods were evaluated thermal properties and crystalline structure of PLA/NF composites, depending on the amount of natural fibres within the weight ratio of 10% up to 30%. We observed that hemp and banana fibres work like natural nucleating agents and thus subsequently improve the material properties of PLA. We also observed process of melt (primary) and cold (secondary) crystallization of PLA/NF composites depending on cooling rate.

Corrosion inhibition of Eleusine aegyptiaca and Croton rottleri leaf extracts on cast iron surface in 1 M HCl medium

Abstract The adsorption and corrosion inhibition activities of Eleusine aegyptiaca ( E. aegyptiaca ) and Croton rottleri ( C. rottleri ) leaf extracts on cast iron corrosion in 1 M hydrochloric acid solution were studied first time by weight loss and electrochemical techniques viz., Tafel polarization and electrochemical impedance spectroscopy. The results obtained from the weight loss and electrochemical methods showed that the inhibition efficiency increased with inhibitor concentrations. It was found that the extracts acted as mixed-type inhibitors. The addition of halide additives (KCl, KBr, and KI) on the inhibition efficiency has also been investigated. The adsorption of the inhibitors on cast iron surface both in the presence and absence of halides follows the Langmuir adsorption isotherm model. The inhibiting nature of the inhibitors was supported by FT-IR, UV–vis, Wide-angle X-ray diffraction and SEM methods.

DSC, WAXD and SEM studies of biodegradation of poly(l-lactide–glycolide–trimethylene carbonate) shape memory terpolymer

Presented study is a part of structural project devoted to elaborating the basis of manufacturing technology of l-lactide–glycolide–trimethylene carbonate polymer system—a novel full biodegradable and resorbable shape–memory polymers. In this paper we took an attempt to describe the transformation of structure of studied shape–memory terpolymers under the influence of the process of biodegradation that occurred in time of implantation samples using first of all the differential scanning calorimetry and supplementary—the wide angle X-ray diffraction and scanning electron microscopy methods. After a 5-year-period of ageing the distinct increase of crystallinity of fibres was found.

Compatibilized ethylene-propylene-diene terpolymer nanocomposites containing different type of organoclays

Summary — The simple mixing of non-polar rubber and organically modified nanoclay may not lead to good dispersion of organoclay in the rubber matrix, which is due to the incompatibility between the rubber and the filler. Thus, the application of polar compatibilizer which is compatible with both the gum base and organically modified clay may help to increase the reinforcing efficiency of the organoclay. Oil extended carboxylated styrene-butadiene rubber (XSBR) was used as a compatibilizer for the dispersion of the organically modified clay (Cloisite 15A, Cloisite 20A and Cloisite 30B) in the ethylene-propylene-diene terpolymer (EPDM) matrix. The degree of dispersion of organoclays in non-polar EPDM matrix after application of polar compatibilizer as well as the influence of these organoclays on the properties of nanocomposites based on EPDM were analyzed in this study. The microstructure of the organoclay filled EPDM composites was studied by wide angle X-ray diffraction (WAXD) method and high resolution transmission electron microscopic (HR-TEM) analysis. Dynamic mechanical thermal analysis (DMTA), scanning electron microscopic (SEM) analysis, thermogravimetric analysis (TGA) and curing tests were conducted for each nanocomposite. Cloisite 30B filled EPDM composite showed best thermal, mechanical and dynamic mechanical properties compared to all other investigated nanocomposites.

Liquid crystalline polyureas with oligo(ethylene glycol) sequences

AbstractA diamine monomer containing ester, amide and ether functional groups was prepared and its polymerization reaction with different diisocyanates to give main chain poly(ester amide ether urea)s was investigated. The monomer was synthesized via reaction of terephthaloyl chloride with 4-hydroxybenzoic acid and subsequent reaction of the resulted diacid with 1,8-diamino-3,6-dioxaoctane. The polymers were characterized by FT-IR and 1H-NMR spectroscopic method and elemental analysis. The resulting polymers exhibited excellent solubility in polar solvents. Crystallinity of the resulted polymers was evaluated by wide-angle X-ray diffraction (WXRD) method, and they exhibited semi-crystalline patterns. The glass transition temperatures (Tg) of the polymers determined by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were in the range of 88-112 °C. The temperatures for 10% weight loss (T10) from their thermogravimetric analysis (TGA) curves were found to be in the range of 297-312 °C in air. Also the prepared polyureas showed liquid crystalline character.

Cooling rate effect on the phase transitions in a polymer liquid crystal: DSC and real-time MAXS and WAXD experiments

The importance of the cooling rate for the structural transformations in a main-chain poly(hexamethylene-4,4′-bibenzoate) has been presented. Detailed analysis of the phase transitions, main structural parameters and their temperature changes has been performed by differential scanning calorimetry, real-time middle-angle X-ray scattering and wide-angle X-ray diffraction methods. The thermodynamic nature of the initial transformation into a smectic A phase has been discussed. The material in the smectic state is supposed to be organized in smectic domains. The crystallization from the smectic phase depends strongly on the kinetics. The crystallization inside the smectic domains results into different final structures determined by the cooling rate applied. At the highest cooling rates, only one crystalline form has been observed. Different possible modifications have been discussed for the case: either a γ-polymorphic form or still some mesophase of high order, as a frozen metastable state. There is a possibility that the phase might be also identified as a condis crystal. At decreasing cooling rates, a new crystalline form, named α∗, appears together with the first one. Lowering the cooling rate, the volume fraction of the α∗-polymorph gradually increases, at the expenses of the first form. The interesting feature of the new observed α∗-polymorph is that it has some similarities with α- and δ-phases of the same material. Contrary to the previous observations, no γ ⇄ α ∗ transformation has been observed neither during the course of single crystallization nor during the subsequent heating. A model describing the gradual transformation of the material during its temperature treatment has been proposed.

The change in characteristics of microcrystalline cellulose during wet granulation using a high-shear mixer.

The objective of this study was to investigate the mechanism of hard granule formation and to demonstrate the applicability of X-ray diffraction methods for studying the polymeric pharmaceutical excipients. Using a high-shear mixer, microcrystalline cellulose (MCC) was granulated with water as the granulating liquid. The hardness of the MCC granules increased with granulation time and the amount of water added. The specific surface area measured by the N2 adsorption method was reduced during the process. Crystallite size of cellulose, calculated by Scherrer's equation adapted for wide angle X-ray diffraction method, decreased with granulation time and with increasing amounts of water added. Debye plots for X-ray small scattering patterns suggested that the average magnitude of the continuous solid region in MCC granules became significantly greater, whereas the specific surface area of the MCC granules, calculated from Debye plots, became smaller in comparison with that of intact MCC. These findings suggested that the long-chain structures in MCC were disrupted, resulting in smaller units with shorter chain lengths due to the strong shear force of the impeller. These smaller units then form a network within the granules. Thus, MCC granules are strengthened with longer granulation time and greater amounts of water, resulting in a more intricate network. The change in MCC chain length and physical structure can be experimentally detected using the small-angle X-ray scattering and wide-angle powder X-ray diffraction methods.

Equipment for investigations of biological nanostructures by diffraction methods using synchrotron radiation

This paper reports on the experimental and methodical developments intended for the small-angle time-resolved station DICSI (“diffraction movie“) at the K1.3a beamline of the Siberia-2 storage ring at the Russian Research Centre “Kurchatov Institute.“ The principles of operation of the optical geometric and detecting systems, as well as the control and recording system, as applied to the investigation of the dynamics of biological nanostructures, have been considered in detail. A new version of the two-coordinate detecting system based on the designed highly effective fluorescent screen (Gd2O2S: Tb) and a CSDU-429 digital camera has been developed. The advantage of this recording system over the Image Plate detecting system in phenomenological investigations is that the optical images obtained on X-ray fluorescent screens with the use of cooled CCD/CMOS arrays can be directly entered into a computer. The detecting system has been tested on different samples by small- and wide-angle X-ray diffraction methods with the use of synchrotron radiation of the VEPP-3 storage ring at the Siberian Synchrotron Center (Novosibirsk, Russia) and the Siberia-2 storage ring at the Kurchatov Center for Synchrotron Radiation and Nanotechnology (Moscow, Russia). Different modifications of original two-coordinate recording systems have been used in systematic studies of the structural dynamics of biological tissues.