Wide-angle X-ray Diffraction Studies Research Articles

A wide angle x-ray diffraction (WAXD) study of thermal and chemical actuation of a shape memory polymer

Abstract The one way effect of the shape memory polymer ESTANE ETE 75DT3 (abbreviation: SMP-E) can be chemically triggered by exposure to methanol, ethanol, and 1-propanol. The present study uses wide angle x-ray diffraction to confirm that programming induces oriented structure in an initially amorphous state. During subsequent shape recovery the sharp diffraction intensity peaks of the programmed state weaken, and oriented amorphous structure is partly lost. This corresponds to the finding that initial shapes cannot be fully recovered. The present work shows that the uptake of small alcohol molecules not only triggers shape recovery but also weakens intermolecular bonds, which results in strength decreasing. From the alcohol concentrations that were measured by weight gain studies, it can be concluded that the key parameter that governs the mechanical and functional behavior of SMP-E is the number of C-atoms that the SMP-E takes up. It is shown that thermal shape recovery is more effective than chemical shape recovery. Chemically triggered shape recovery can be used to lift small end loads corresponding to stresses of up to 1 MPa. The results are discussed in the light of previous work published in the literature.

Novel Quaternary Ammonium Derivatives Based on Apple Pectin.

New quaternary ammonium derivatives (quats) based on apple pectin (PA) were synthesized by the chemical modification of native polysaccharides with various quaternization mixtures containing epichlorohydrin (ECH) and a tertiary amine. Pectin derivatives (QPAs) were studied by elemental analysis, conductometric titration, Fourier-transform infrared spectroscopy (FTIR), and 13C nuclear magnetic resonance (13C NMR). Viscosity measurements enabled the evaluation of the viscosity average molar mass (Mv) for the unmodified polysaccharide, as well as its intrinsic viscosity ([η]) value. Dynamic light scattering (DLS) analysis revealed that the PA and its quats formed aggregates in an aqueous solution with either a unimodal (PA) or bimodal (QPAs) distribution. Scanning transmission electron microscopy analysis (STEM) of the PA and its derivatives demonstrated the presence of individual polymeric chains and aggregates in aqueous solution, with the smallest sizes being specific to amphiphilic polymers. Thermal stability, as well as wide-angle X-ray diffraction (WAXD) studies, generally indicated a lower thermal stability and crystallinity of the QPAs compared with those of the PA. Antipathogenic activity demonstrated that the PA and its derivatives exhibited effectiveness against S. aureus ATCC 25923 bacterium and C. albicans ATCC 10231 pathogenic yeast.

Mercaptoethanol-assisted synthesis of sulfonic acid-functionalized polysiloxanes as inorganic fillers in composite membranes for energy-storage applications

Developing proton-exchange membranes (PEMs) for energy applications is necessary for fulfilling the increasing energy demand without environmental effects. In this study, we prepared composite membranes containing mercaptoethanol-assisted sulfonic acid-functionalized polysiloxanes (MASFPs) and perfluorinated sulfonic acid (PFSA). The MASFP-containing composite membrane (i.e., CMASFP-2) exhibited better membrane properties than the composite membrane prepared without mercaptoethanol (CMASFP-1) and the reference Nafion 212 membrane. Wide-angle X-ray diffraction (XRD) studies revealed a broad peak at 2θ = 17.4° and 39°, indicating that the composite membranes are semicrystalline. Scanning electron microscopy (SEM) analysis revealed that the prepared composite membranes had good morphology, whereas energy-dispersive X-ray spectroscopy analysis revealed that it had siloxane and more sulfonic acid than the pristine PFSA membrane. Thermogravimetric and mechanical strength analyses revealed that incorporating sulfonic acid-functionalized siloxanes improved the thermal stability and mechanical strain of the membrane. The prepared CMASFP-2 membrane had a high ionic conductivity of 0.106 mS cm−1 and an ion-exchange capacity of 1.09 meq·g−1. CMASFP-2 also exhibited lower hydrogen gas permeability than the Nafion 212 and PFSA membranes, demonstrating that it can be used for energy applications.

Multiscale insights into electric field orientation effects on piezoelectric strain and crystallography in P(VDF–TrFE) and P(VDF–TrFE–CTFE) fibers

This research primarily focuses on the effect of changing electric field directions on the crystal structure of piezoelectric fibers, notably, P(VDF–TrFE) and P(VDF–TrFE–CTFE). The study also explores the deformation mechanisms of fibers at micro- and nanoscales. A significant aspect of the research involves the application of parallel and perpendicular electric fields and observation of their impact on fiber properties. In situ wide-angle X-ray diffraction (WAXD) studies are crucial for determining the nanoscale properties when the electric field orientations change. The results show that the direction of the electric field significantly affects the sign (positive or negative) of the dipole vector within the β-crystal lattice structure of the fibers. This can be attributed to the rotation of dipole vectors in response to the electric field–fiber alignment angle. Furthermore, the research identifies the crystal plane (201,111)β as exhibiting the highest magnitude of piezoelectric response strain in the β phase. The study also employs scanning electron microscopy and digital image correlation (DIC) to reveal the material's morphology and to assess fiber strain distribution at the micrometer scale under different voltages. DIC results particularly highlight that stress concentration leads to the deformation of fibers into voids, which are spaces between fibers created by electrospinning. This work comprehensively elucidates how deformation works in piezoelectric polymers by connecting large-scale changes observed in fibers through DIC and small-scale changes observed in WAXD studies presenting the piezoelectric strain responses at the crystal plane.

Concentration-tuned diverse response to selective biogenic amines using a reusable fluorophore: monitoring protein-rich food spoilage.

Maintaining the freshness of food is essential for a healthy and quality life. Nevertheless, it remains a global challenge. Hence, an easy detection and monitoring protocol would be highly desirable. A cyanoacrylic acid (CAA)-based fluorophore is manifested as a reusable platform that responds diversely against different concentrations of selective aliphatic biogenic amines (BAs) in both solution and vapor phases. Slow spoilage of the protein-rich food is progressively monitored through emission shifts visible to the naked eye. This fluorophore provides easy and naked-eye detection of the BA vapor through a change in emission, i.e., red → orange → orange-yellow → cyan → green and quantum yield enhancement, which occur in stepwise increments of vapor concentrations. The probe design includes π-conjugated functionalized fluorescent molecules linked to multiple twisting sites, resulting in both solid and solution-state emission. The attached carboxylic acid responds quickly with selective BAs, mainly putrescine (PUT), cadaverine (CAD), and spermidine (SPM), where the concentration-based emission variation has appeared to be distinct and prominent against PUT [sensitivity (μM): 2 (solution); 3.3 (vapour)]. The selectivity towards diamine can be clarified by the formation of carboxylic acid salts and the consequent proton exchanges between free and protonated amines. In addition, -CN···H interaction is likely to develop within this ammonium carboxylate system, providing extra stability. Such ammonium carboxylate salt formation and gradual change in the molecular arrangement, resulting in symmetry development, are validated by FT-IR and wide-angle X-ray diffraction studies. Besides, this fact is supported by DFT studies that validate intramolecular H-atom exchange between free amine and ammonium salt units. A fluorophore-coated coverslip, filter paper, or silica gel-coated Al-plate is fruitfully utilized to detect the freshness of fish and chicken, which reveals the potential of this probe to prevent food waste and control food safety.

Influence of low contents of cellulose nanocrystals on the crystallization behavior of biobased Poly(propylene 2,5-furandicarboxylate)

To address the slow crystallization problem of poly(propylene 2,5-furandicarboxylate) (PPF), fully biobased PPF/cellulose nanocrystals (CNC) composites were prepared via a solution and casting method in this work at low CNC contents. The influence of CNC on the crystallization of PPF was studied in detail under various conditions, including nonisothermal and isothermal melt crystallization as well as nonisothermal and isothermal cold crystallization. The results revealed that the crystallization of PPF was enhanced under various crystallization conditions by CNC due to the heterogeneous nucleating agent role. From the isothermal crystallization kinetics study, the presence of CNC did not alter the crystallization mechanism of PPF. In addition, the thermogravimetric analysis results showed that both PPF and PPF/CNC composites displayed an excellent thermal stability. On the basis of the wide angle X-ray diffraction study, CNC did not change the crystal structure of PPF.

Water Influence on the Physico-Chemical Properties and 3D Printability of Choline Acrylate-Bacterial Cellulose Inks.

The aim of this work was to study the influence of water as a co-solvent on the interaction between a polymerizable ionic liquid-choline acrylate (ChA)-and bacterial cellulose. Bacterial cellulose dispersed in ChA is a new type of UV-curable biopolymer-based ink that is a prospective material for the 3D printing of green composite ion-gels. Higher cellulose content in inks is beneficial for the ecological and mechanical properties of materials, and leads to increased viscosity and the yield stress of such systems and hampers printability. It was found that the addition of water results in (1) a decrease in the solvent viscosity and yield stress; and (2) a decrease in the stability of dispersion toward phase separation under stress. In this work, an optimal composition in the range of 30-40 wt% water content demonstrating 97-160 Pa of yield stress was found that ensures the printability and stability of inks. The rheological properties of inks and mechanical characteristics (0.7-0.8 MPa strength and 1.1-1.2 MPa Young's modulus) were obtained. The mechanism of influence of the ratio ChA/water on the properties of ink was revealed with atomic force microscopy, wide-angle X-ray diffraction studies of bacterial cellulose after regeneration from solvent, and computer simulation of ChA/water mixtures and their interaction with the cellulose surface.

Influence of Thermal Annealing on the Sinterability of Different Grades of Polylactide Microspheres Dedicated for Laser Sintering.

We present a comparison of the influence of the conditioning temperature of microspheres made of medical grade poly(L-lactide) (PLLA) and polylactide with 4 wt % of D-lactide content (PLA) on the thermal and structural properties. The microspheres were fabricated using the solid-in-oil-in-water method for applications in additive manufacturing. The microspheres were annealed below the glass transition temperature (Tg), above Tg but below the onset of cold crystallization, and at two temperatures selected from the range of cold crystallization corresponding to the crystallization of the α’ and α form of poly(L-lactide), i.e., at 40, 70, 90, and 120 °C, in order to verify the influence of the conditioning temperature on the sinterability of the microspheres set as the sintering window (SW). Based on differential scanning calorimetry measurements, the SWs of the microspheres were evaluated with consideration of the existence of cold crystallization and reorganization of crystal polymorphs. The results indicated that the conditioning temperature influenced the availability and range of the SWs depending on the D-lactide presence. We postulate the need for an individual approach for polylactide powders in determining the SW as a temperature range free of any thermal events. We also characterized other core powder characteristics, such as the residual solvent content, morphology, particle size distribution, powder flowability, and thermal conductivity, as key properties for successful laser sintering. The microspheres were close to spheres, and the size of the microspheres was below 100 µm. The residual solvent content decreased with the increase of the annealing temperature. The thermal conductivities were 0.073 and 0.064 W/mK for PLA and PLLA microspheres, respectively, and this depended on the spherical shape of the microspheres. The wide angle X-ray diffraction (WAXD) studies proved that an increase in the conditioning temperature caused a slight increase in the crystallinity degree for PLLA microspheres and a clear increase in crystallization for the PLA microspheres.

Lipase-Catalyzed Fully Aliphatic Copolyesters Based on Renewable Isohexide Isomers

Isohexides are versatile carbohydrate-based building blocks for designing biodegradable polymers with tunable biodegradability and enhanced material properties owing to their unique high structural rigidity and hydrophilicity. However, the limited reactivity and thermal stability of isohexides, especially the isomers with endo-hydroxyl groups, hamper their practical applications. In this work, fully aliphatic copolyesters based on two isohexide stereoisomers, isosorbide (IS) and isomannide (IM), were comparatively synthesized via a mild lipase-catalyzed polymerization [enzymatic polymerization (EP)] technique. The products were obtained with fairly high molecular weights (Mn values: 15,300–31,500 g·mol–1), negligible degree of discoloration, and 20–40 °C higher thermal stabilities (Td,5%: 335–360 °C) compared to those of their counterparts obtained by melt polymerization (MP). Molecular dynamics (MD) simulation revealed that the endo-OH is preferred to the exo-OH under the EP process having a high hydrogen-bonding frequency with the catalytic site of CALB (lipase immobilized from Candida antarctica, CALB), and it also requires considerably low energy (70–100 kJ·mol–1) to form the second tetrahedral transition-state intermediates. The wide-angle X-ray diffraction (WAXD) study further elucidates the interesting influence of the EP process on inducing specific β-type crystalline structures.

Flower- and Grass-like Self-Assemblies of an Oleanane-Type Triterpenoid Erythrodiol: Application in the Removal of Toxic Dye from Water.

Erythrodiol (3β-olean-12-ene-3, 28-diol) (C30H50O2) 1 is a nanosized oleanane-type fused 6-6-6-6-6 pentacyclic triterpeneoid extractable from the dried leaves of olive (Olea europia). One step reduction of oleanolic acid extracted from Lantana camara also yields the same compound. The triterpenoid has one secondary −OH group attached at C3 of the “A” ring and one primary −OH group at C28 present at the junction of the “D” and “E” rings. Here, we report the spontaneous self-assembly of erythrodiol in different neat organic liquids and aqueous-organic liquid mixtures. The nanosized dihydroxy triterpenoid having an oleanane-type lipophilic rigid skeleton self-assembled in liquids, yielding nanosized fibrils, microsized flowers, and grass-like architectures via formation of densely assembled fibrils and petals or 2D sheets. The microstructures of the self-assemblies have been characterized by different techniques like optical microscopy, electron microscopy, atomic force microscopy, FTIR, and wide angle X-ray diffraction studies. The porous self-assemblies having a large surface area obtained from 1 were capable of adsorbing toxic fluorophores like rhodamine-B, rhodamine-6G, methylene blue, and crystal violet (CV). Moreover, removal of the aforementioned toxic pigments has also been demonstrated from their aqueous solutions by using UV–visible spectrophotometry and epifluorescence microscopy.

Penetration Process of a Hydrated Deep Eutectic Solvent Through the Stratum Corneum and its Application as a Protein Penetration Enhancer.

The penetration mechanism of choline chloride‐glycerol deep eutectic solvent (DES) through the stratum corneum (SC) as a potential solvent for a novel enhancer of protein penetration into the skin was investigated in a wide and small angle X‐ray diffraction study. We found that DES penetrated through intercellular lipids but not the corneocytes. DES seemed to extract a portion of lipids of the short lamellae in the SC. Hydrated DES with a DES to water weight ratio of 9 to 1 (9DES‐1H2O) showed the strongest interaction with the lipids in the SC compared with water, DES, and hydrated DESs with another weight ratio of DES to water (DES : water=8 : 2). In a skin penetration test with a fluorescently labelled lysozyme, 9DES‐1H2O increased the amount of penetration through the SC by two‐fold compared with HEPES buffer.

Effect of α-Fe2O3 nanoparticles on the mechanism of charge storage in polypyrrole-based hydrogel

A hybrid hydrogel based on polypyrrole and hydrothermally prepared α-Fe2O3 nanoparticles was synthesized via in situ chemical polymerization of pyrrole using sodium trimetaphosphate as a crosslinker. Wide-angle X-ray diffraction study confirmed the presence of α-Fe2O3 in the prepared material. Mapping of the elemental composition using energy dispersive X-ray spectroscopy showed the uniform distribution of the inorganic particles inside the polypyrrole matrix. The effect of α-Fe2O3 on the structure of the hybrid hydrogel and on the mechanism of charge storage was studied with scanning electron microscopy, cyclic voltammetry, galvanostatic charge–discharge and impedance spectroscopy. The specific capacitance was found to increase from 250 F g−1 for the polypyrrole hydrogel up to 509 F g−1 for the α-Fe2O3-doped hydrogel at the current density of 0.2 A g−1. The hematite incorporation also affected the morphology of the hydrogel leading to a slight increase in the double-layer capacitance accompanied with a strong increase in the pseudocapacitance: from 239 F g−1 up to 486 F g−1. The initial polypyrrole hydrogel and the hybrid hydrogel demonstrated a capacitance retention of about 75% and 79% after 3000 charge–discharge cycles at the current density of 4 A g−1, respectively.

An efficient two-scale 3D FE model of the bone fibril array: comparison of anisotropic elastic properties with analytical methods and micro-sample testing.

In this study, 3D finite element analyses (FEA) are conducted to quantify the orthotropic elastic properties and investigate the load transfer mechanism of bone at the sub-lamellar level. Three finite element (FE) unit cells with periodic boundary conditions are presented to model a two-scale microstructure of bone including a mineralized collagen fibril (MCF), the extrafibrillar matrix (EFM) and the resulting fibril array (FAY) under arbitrary loading. The axial and transverse elastic properties of the FAY computed by FEA are calibrated with unique experimental results on ovine micro-samples showing a coherent fibril orientation. They are then systematically compared with those calculated using analytical methods including the basic Voigt, Reuss and shear-lag models, the Mori-Tanaka scheme and the upper and lower bounds by Hashin and Shtrikman. The predicted axial strain ratios between the two-scales are discussed with respect to a recent small-angle X-ray scattering and wide-angle X-ray diffraction study. Beyond apparent elastic properties, the FE models provide stress distributions at both hierarchical levels, confirm the shear lag mechanisms within the MCF and between MCF and EFM and identify potential damage sites under arbitrary loading conditions. A comprehensive sensitivity analysis shows that mineral volume fraction in the fibril array is the dominant parameter on the axial and transverse elastic moduli, while the MCF volume fraction in FAY is the most sensitive variable for the ratio of axial versus transverse elastic modulus followed by the elastic moduli of hydroxyapatite and collagen. The FE model of the FAY developed and calibrated in the current study represents an anatomically realistic, experimentally validated and computationally efficient basis for investigating the apparent yield, post-yield and failure behaviors of lamellar bone in future research.

Effect of Initial Conformation on the Starch Biopolymer Film Formation Studied by NMR.

The formation of a rigid porous biopolymer scaffold from aqueous samples of 1% w/v (suspension) and 5% w/v (gel) corn starch was studied using optical and nuclear magnetic resonance (NMR) techniques. The drying process of these systems was observed using a single-sided NMR scanner by application of the Carr–Purcell–Meiboom–Gill pulse sequence at different layer positions. The echo decays were analyzed and spin–spin relaxation times (T2) were obtained for each layer. From the depth dependent T2 relaxation time study, it was found that the molecular mobility of water within the forming porous matrix of these two samples varied notably at different stages of film formation. At an intermediate stage, a gradual decrease in mobility of the emulsion sample towards the air–sample interface was observed, while the gel sample remained homogeneous all along the sample height. At a later stage of drying, heterogeneity in the molecular dynamics was observed in both samples showing low mobility at the bottom part of the sample. A wide-angle X-ray diffraction study confirmed that the structural heterogeneity persisted in the final film obtained from the 5% corn starch aqueous sample, whereas the film obtained from the 1% corn starch in water was structurally homogeneous.

Tangled silver nanoparticles embedded polythiophene-functionalized multiwalled carbon nanotube nanocomposites with remarkable electrical and thermal properties

Tangled silver nanoparticles embedded layered polythiophene-functionalized multiwalled carbon nanotube ternary nanocomposite (PTCNT-COOH 300 Ag) has been prepared by ascorbic acid reduction of silver nitrate solution in presence of aqueous dispersion of polythiophene-functionalized multiwalled carbon nanotube (PTCNT-COOH) binary nanocomposites. Binary polythiophene–functionalized multiwalled carbon nanotube nanocomposites have been prepared by in-situ chemical oxidative polymerization of thiophene monomer stabilized by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) micelles in presence of functionalized multiwalled carbon nanotubes (MWCNT-COOH) using ferric chloride (FeCl3) as an oxidizing agent in chloroform solvent. The structural formation and composition of binary and ternary nanocomposites have been confirmed by fourier transform infrared spectroscopy, fourier transform Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and wide angle X-ray diffraction studies. Scanning electron microscopy (SEM) studies have revealed the nanofibrous morphology in binary nanocomposites (PTCNT-COOHs), whereas in ternary nanocomposite (PTCNT-COOH 300 Ag), silver nanoparticles were densely embedded as nanoparticles over nanofibrous structure. Transmission electron microscopic (TEM) images have provided the evidence regarding silver nanoparticles that existed in a tangled state over the nanofibrous structure. Stable dispersion of binary nanocomposites (PTCNT-COOHs) in water, ethanol and chloroform enabled us to record the UV–visible absorption spectra which have shown two peaks at 260 nm and 360 nm corresponding to π-π* transition from aromatic rings and π-polaron absorption of polythiophene respectively. On the other hand, ternary nanocomposite have shown surface plasmon resonance as broad peak tailing to 550 nm. The electrical conductivity of nanocomposites PTCNT-COOH 100 (binary nanocomposite), PTCNT-COOH 200 (binary nanocomposite), PTCNT-COOH 300 (binary nanocomposite), pristine MWCNT, functionalized MWCNT-COOH, MWCNT-COOH Ag (binary nanocomposite) and PTCNT-COOH 300 Ag (ternary nanocomposite) were 4.42 × 10−2, 5.30 × 10−1, 1.64, 8.66, 2.80, 12.40 and 80.76 S/cm respectively. The enhanced electrical conductivity of ternary nanocomposite was due to the effective charge transport through polythiophene layer which act as conductive bridge between multiwalled carbon nanotube and silver nanoparticles. Thermogravimetric analysis have revealed that high thermal stability of ternary silver nanocomposite of PTCNT-COOH 300 Ag up to 620 °C for 10% weight loss. Silver nanoparticles embedded ternary nanocomposite in basic medium shows least leaching effect, therefore it could be potentially useful in catalytical applications.

Impact of synergism of LDH with PNCC on the thermal and mechanical properties of polyester nanocomposites

ABSTRACTPresent study investigates, the synergistic effect of Precipitated Nano Calcium Carbonate with Layered Double Hydroxides (LDHs) on thermal and mechanical properties of unsaturated polyester resin. A polyester-LDH-PNCC nanocomposite was prepared using “slurry-compounding” method. Meanwhile, PNCC was prepared by in-situ deposition (matrix-mediated growth and controlled) technique, crystal dimension of PNCC was estimated by using Transmission Electron Microscope (TEM). Surface morphology and mechanical properties were studied by using Field Emission Scanning Electron Microscopy (FESEM) and Universal Tensile Machine (UTM) respectively. Wide angle X-ray diffraction (WAXD) study revealed the formation of polyester nanocomposites. The nanocomposites showed better thermal and mechanical properties than that of the unmodified polyester resin, thus, synergism of LDH-PNCC influenced thermal and mechanical properties of polyester nanocomposites.

Specifics of the Surface of Tire Crumb Regenerate Produced by the Explosive Circulation Method

A complex analysis of the crumbed rubber produced by the explosive circulation method has been performed by the methods of AFM, X-ray diffraction, gas chromatography, mass spectrometry, and gel-permeation chromatography (GPC). The results of the small- and wide-angle X-ray diffraction study have revealed an amorphous structure of the samples without supramolecular ordering at a distance scale of ~1–40 nm. Globular formations of a size of 5–20 nm on the crumb surface combined into clusters of various shapes and sizes in the range 100–1000 nm have been found by means of the AFM method. Individual nanoglobules and small and large clusters of these nanoglobules appeared to be randomly covering the surface of the examined samples. It has been established that the nanoglobules partially consist of saturated and unsaturated hydrocarbons of low-molecular weight, which belonging to classes of linear, cyclic, and aromatic compounds. Most of the nanoglobules are represented by oligomeric products having 3–5 units, as well as compounds of higher molecular weight. All of the above compounds provide better adhesion of the regenerate to different matrices than that produced by other methods. The composition of the nanoscaled globules includes secondary products of reactions of low-molecular hydrocarbons formed from rubber tires at their explosive circulation grinding.

Crystallization and crystalline dynamics of poly(3-hydroxybutyrate) / poly(4-vinylphenol) polymer blends studied by low-frequency vibrational spectroscopy

Composition- and temperature-dependent far-infrared (FIR), terahertz (THz), and low-frequency Raman spectra of poly(3-hydroxybutyrate) (PHB)/Poly(4-vinylphenol) (PVPh) polymer blends were measured to investigate the effects of PVPh in PHB crystallization. FIR, low-frequency Raman, and wide angle X-ray diffraction (WAXD) studies revealed that PVPh reduces the crystallinity of PHB in blends without a significant change in the crystal structure. The FIR and low-frequency Raman spectra divided the blends into three categories: high-ordered crystalline, less-ordered crystalline, and amorphous. A new peak was observed at 135 cm−1 in the FIR spectra of the PHB/PVPh blends, which may be assigned to the less-ordered crystalline phase of PHB, predicting the inter-molecular hydrogen-bond interactions of PHB/PVPh. The intensity ratio of the peaks at 97 and 82 cm−1 changed with the blending ratio variations owing to the crystalline dynamics of PHB. Deformation of the PHB helical structure occurred first, followed by weakening of the intra-molecular hydrogen-bond within PHB. Shifts of several peaks were observed in the FIR and low-frequency Raman spectra, suggesting that the intra-molecular hydrogen-bond (CO⋯H-C-) within PHB weakened with temperature. The novelty of the present study is to demonstrate that low-frequency vibrational spectroscopy is very sensitive to monitor changes from the intra-molecular hydrogen bonding to inter-molecular hydrogen bonding between PHB and PVPh.

Structural evolution of stretch deformed HDPE/RGO nanocomposites: An in-situ synchrotron SAXS and WAXD study

We have reported that the incorporation of reduced graphene oxide (RGO) can induce epitaxial crystallization of high density polyethylene (HDPE) on RGO surfaces and then enhance mechanical properties of HDPE/RGO nanocomposites, but the underline intensifying mechanism remains unclear. Herein, to further unveil the influence of epitaxial crystallization imposing on the improvement of mechanical properties, the structural evolution of HDPE/RGO nanocomposites during the stretching process is explored as a function of RGO content by in-situ synchrotron wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) techniques. It has shown that the introducing of RGO apparently retards the structural evolution in the tensile deformation and the hysteresis is accentuated dramatically with increasing RGO content. The epitaxial growth of HDPE upon RGO surfaces forms large sized crystals and the amount of epitaxial crystals enlarges with RGO content. The coupling of the remained existence of large sized crystals and the smaller density after stretching demonstrates that the interplay between RGO and large amount of epitaxial crystals can undergo the strong stress and thus hampers and delays the structure change and crystal fragmentation during the tensile deformation of HDPE/RGO nanocomposites. The present results not only makes clear that it is the epitaxial crystallization stemming from interfacial interaction between HDPE and RGO that plays the major role to delay the structural evolution and damage and thus lead to the enhancement of mechanical properties of HDPE/RGO nanocomposites, but reveal the underline stress-induced fragmentation-recrystallization mechanism for this tensile deformation.

Evaluation of Dissolution Enhancement of Aprepitant Drug in Ternary Pharmaceutical Solid Dispersions with Soluplus® and Poloxamer 188 Prepared by Melt Mixing

In the present study Aprepitant (APT) ternary solid dispersions (SDs) were developed and evaluated for the first time. Specifically, ternary SDs of APT with Poloxamer 188 and Soluplus® (SOL) were prepared via melt mixing and compared to binary APT/Poloxamer 188 and APT/SOL SDs. Initially, combined thermo-gravimetric and hot-stage polarized light microscopy studies indicated that all tested compounds were thermally stable up to 280 °C, while Poloxamer 188 acted as a plasticizer to SOL by significantly reducing the temperature required to fully solubilize the API during SD preparation. Differential scanning calorimetry combined with wide angle X-ray diffraction studies showed that crystalline API was dispersed in both binary and ternary SDs, while Fourier transformation-infrared spectroscopy studies revealed no molecular interactions among the components. Scanning electron microscopy combined with EDAX element analysis showed that the API was dispersed in nano-scale within the polymer matrices, while increasing APT content led to increasing API nano-crystals within the SDs. Finally, dissolution studies showed that the prepared formulations enhanced dissolution of Aprepitant and its mechanism analysis was further studied. A mathematical model was also investigated to evaluate the drug release mechanism.