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The possibility of SW formation via a mechanism other than carbon–carbon bond rotation.

Electrochemical nonenzymatic biosensors with no immobilization and degradation problem, have recently attracted growing attention due to stability and reproducibility. Here, a comparative study was conducted to precisely evaluate the nonenzymatic glucose sensing of pure/oxidized Ni, Co, and their bimetal nanostructures grown on electrospun carbon nanofibers (ECNFs). This method provides a low-cost free stand electrode. The prepared nanostructures with superb physiochemical features exhibited sensitivity (from 66.28 to 610.6 μA mM−1 cm−2), linear range of 2-10 mM, limit of detection in the range of 1 mM, and response time (

A new methodology to assess ion diffusion in side-chain modified AEMs reveals separate roles for functionality and side-chain length: the former determines hydrophilic pathway morphology and the latter regulates anion diffusion rate in the channels.

Any improvement in drilling technology is critical for developing the oil and gas industry. The success of drilling operations largely depends on drilling fluid characteristics. Drilling fluids require enough viscosity to suspend the particles and transport them to the surface and enough capability to control the fluid loss into the formation. Rheology and filtration characteristics of drilling fluids are crucial factors to consider while ensuring the effectiveness of a drilling operation. Graphene oxide (GO), xanthan gum (XG), and low-viscosity carboxymethyl cellulose (CMC LV) are being utilized in this research to produce high-performance, low-solid water-based drilling fluids (WDFs). Rheological and filtration behaviors of GO/XG/CMC LV-WDF were investigated as a function of GO, XG, and CMC LV at low concentrations (0.0-0.3% w/w) and atmospheric conditions. According to the findings, GO improved the rheological and filtration capabilities of the WDF. By adding 0.15 wt % GO, shear stress could be doubled, especially at a high shear rate of 1022 s-1. The plastic viscosity of the fluid could be expanded from 6 to 13 centipoise, and a fluid loss of 8.7 mL over 30 min was observed during the API fluid test, which would be lower than the suggested fluid loss value (15.0 mL) for water-based mud. At the same concentration of XG and CMC LV, XG had a more significant influence on rheological characteristics in the presence of GO. Adding 0.3 wt % XG could increase fluid shear stress from 20.21 to 30.21 Pa at a high shear rate of 1022 s-1. In contrast, CMC LV had more impact on filtration properties, acting as a filtration control agent by decreasing the API fluid loss of fluid from 21.4 to 14.2 mL over 30 min. The addition of XG and CMC LV to the GO solution may influence the microstructure of the filter cake, resulting in a tree-root morphology. Indeed, in the GO/CMC LV solution, the individual platelets may bind together, form a jellyfish shape, and block the micropores. The incorporation of CMC LV helped develop compact filter cakes, resulting in excellent filtration. Five rheological models were employed to match the fluid parameters quantitatively. The Herschel-Bulkley model outperformed the other models in simulating fluid rheological behavior. The findings of this study can be utilize to provide low-cost, stable, and environmentally compatible additives for drilling low-pressure, depleted, and fractured oil and gas reservoirs.

Uniform dispersion of nanoplatelets in a polymer matrix is always a great concern in the production of high quality nanocomposites. Graphene oxide (GO) was synthesized by Hummer’s method in a unique way that improved nanoclay dispersion in casting polyvinyl alcohol (PVA) film. Montmorillonite (MMT)-GO/PVA nanocomposites were synthesized by solution-casting method. The addition of a small amount (e.g., 0.25% by wt) of graphene oxide greatly improved nanoclay dispersion and significantly enhanced the mechanical properties of PVA hybrid nanocomposite. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) imaging proved that montmorillonite layers and graphene oxide (GO) sheets were uniformly dispersed in the polymeric matrix and favorably oriented parallel to the surface. X-ray diffraction (XRD) showed that both nanoplatelets were thoroughly exfoliated and uniformly distributed on the surface of nanocomposite films. Differential scanning calorimetry (DSC) indicated a slight degree of PVA crystallinity. While there was a significant improvement in the mechanical properties of the films, for the PVA film with 2.5% (by wt) montmorillonite and 0.25% (by wt) graphene oxide, the advanced mechanical properties were evidence of the synergy of the two nanoplatelets under favorable conditions.

Coordinative polymerization brings opportunities for producing well-defined long-chain branched polyolefins specifically by using homogeneous single-site catalysts. Herein, we report a new dual cat...

Naphtha is one of the crude oil distillation products, bringing almost the lowest value-addition to crude oil, compared to other refinery products such as liquid petroleum gas, gasoline, and diesel. However, Naphtha can be converted to one of the highest value products at the end of the value chain, i.e., polyolefins. Although the production of conventional commodity polyolefins from crude oil, is considered as one of the final products in alkenes’ value chain, there are specialty polyolefins with higher values. Specialty polyolefins are small volume, high-performance thermoplastics with high-profit margins compared to traditional commodity polyolefins. Recently, some special purpose functionalized polyolefins have been developed as efficient substituents for high-performance engineering thermoplastics. Polyolefins are exploited as cost-effective platforms to produce these functionalized thermoplastics. They are promising candidates for replacing high-performance polymers with high-cost raw materials and elaborate production processes. So, functional polyolefins have introduced a new paradigm in the production of high-performance thermoplastics, extending the alkenes’ value chain and increasing profitability. High-performance specialty polyolefins may find exceptional markets in niche applications. In this chapter, the commercial specialty and functional polyolefins’ current situation and prospects are reviewed.

A thin film sensor based on hollow polyaniline nanofibers is fabricated for ammonia sensing applications at room temperature (25 °C). Polyaniline nanotubular structures (H.PANI) are synthesized via in-situ chemical polymerization method with the inner diameter of 200–300 nm and the outer diameter of 350–450 nm. FE-SEM, FTIR, and XRD tests are performed to analyze the H.PANI structure. To investigate the effect of structure on gas sensing performances, H.PANI sensor is compared with the polyaniline powder (P.PANI) sensor. The measured LOD of H.PANI sensor is 81 ppb, which is an indication that it can be used in various applications. There is a great proton exchange between H.PANI and ammonia gas due to its high surface to volume ratio, leading to high sensitivity. The response of the H.PANI and P.PANI sensors at one ppm ammonia are about 3.36% and 1.26%, respectively.

The significant breakthroughs of flexible gel electrolytes have attracted extensive attention in modern wearable electronic gadgets. The lack of all-around high-performing gels limits the advantages of such devices for practical applications. To this end, developing a multi-functional gel architecture with superior ionic conductivity while enjoying good mechanical flexibility is a bottleneck to overcome. Herein, an architecturally engineered gel, based on PVA and H3PO4 with different molecular weights of PVA for various PVA/H3PO4 ratios, was developed. The results show the dependence of ionic conductivity on molecular weight and also charge carrier concentration. Consequently, fine-tuning of PVA-based gels through a simple yet systematic and well-regulated strategy to achieve highly ion-conducting gels, with the highest ionic conductivity of 14.75 ± 1.39 mS cm-1 have been made to fulfill the requirement of flexible devices. More importantly, gel electrolytes possess good mechanical robustness while exhibiting high-elasticity (%766.66 ± 59.73), making it an appropriate candidate for flexible devices.

Tuning the bimodality of microstructural features in polymers has provided novel properties and applications. A classic example is to overcome the trade-off between processability and mechanical properties in polyolefins. A recent example is to decrease the interfacial tension in blending incompatible polymers. Therefore, the development of a bimodality index (BI), especially for the chain length distribution (CLD) and the chemical composition distribution (CCD), is crucial for the quantitative design of materials. This study introduces quantitative expressions for the bimodality of univariate CLD on the linear scale, and CCD. Moreover, we develop a bimodality criterion for bivariate CLD–CCD while representing it graphically and analytically. As such, this analysis applies to linear polymers whose CLD–CCD is expressed by the Stockmayer bivariate distribution. Our results indicate that a specific chain length exists beyond which the CCD part of bivariate distribution becomes bimodal. Mathematical modelling of ethylene-propylene copolymerization in two loop reactors in series, operating at different conditions, was used to provide representative examples and to verify the suggested bimodality indices. We calculate the developed bimodality indices at representative operation conditions and compare them with the model bivariate distributions. The developed bimodality indices facilitate designing new products with bimodal microstructural features and are also beneficial for developing novel characterization techniques and providing a better understanding of the structure–property relationships in bimodal polymers.

In this research, the fabrication of a hybrid structure of polyaniline hollow fibers (PANI-HF) and reduced graphene oxide (rGO) has been reported and the hierarchical structure and electrochemical performance of the system has also been studied. The formation of the hierarchical hybrid structure has been proved by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), fourier transform infrared (FTIR), and X-ray diffraction (XRD). Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS) and cyclic stability were employed to evaluate the electrochemical performance of the composites. PANI-HF has provided a superior structure for enhanced electrocapacitance due to its higher specific surface area. Decorating the PANI-HF by rGO sheets has resulted in better specific capacitance (Cs) at high scan rates. At the scan rate of 20 mV s−1, the specific capacitance of PANI-HF/rGO hybrid was found to be 449 F g−1 while it was 425 F g−1 for PANI-HF. Furthermore, rGO has provided a solid network in hybrid sustaining PANI-HF during the long-term charge-discharge cycles and improved the cyclic stability. In addition, only 16% of the initial capacitance of PANI-HF/rGO hybrid has been lost after 2000 cycles.

The relationship between rheological properties and structural changes in polyethylene chains due to the recycling of two linear low-density polyethylenes (LL-A and LL-B) has been investigated. These samples were subjected to multiple extrusion processes (9 extrusion steps). According to the results of gel content experiments, crosslinking did not occur. The results of the gel permeation chromatography indicated that the chain scission was slightly predominant during the re-extrusion, while the rheometry results clearly show the effects of long-chain branching during degradation. Therefore, the degradation proceeded through both paths. Based on the rheological results and the Cole-Cole method, LL-B exhibited a higher degradation rate during the extrusion process (because of the low antioxidant content), compared to LL-A. The results of thermorheological methods including van-Gurp-Palmen and activation energy spectra indicated that the extent of thermorheological complexity was intensified with increasing the number of extrusion cycles and consequently increasing the number of long-chain branches.

The surface of pulled out fiber from the cementitious matrix reveals some scratches. It can be considered that the fresh cement paste can penetrate into the pores of hydrophilic poly (vinyl alcohol) (PVA) fibers which is converted to some hard teeth in the pores of the fiber after cement hydration. The hard teeth scratch the fiber surface during pull out which introduce energy consuming and slip hardening. In the current study, some nano-scratches with the length of 3 μm and the depths of 50, 150 and 250 nm are produced on two different PVA fibers the required force at different scratching rates are evaluated. The nano-scratches are made by an innovative inverse fly-mode technique in atomic force microscopy. The results indicate that the required force increases as the hardened teeth is further scratching the fiber which causes the strain hardening. However, the fibers showing significant roughness and high resistance against scratch fail during fiber pull out which deteriorates the strain hardening.

Conductive inks are considered very promising for device fabrication on flexible substrates and large areas. Silver (Ag)-graphene hybrid inks offer many opportunities, including cost/conductivity optimization for different applications. In this work, several conductive hybrid ink formulations containing Ag nanostructures and graphene derivatives were prepared using different processing strategies and thoroughly characterized. SEM and morphological studies were used to explore the probable reasons for the difference in electrical conductivity of various inks. Strong interaction between Ag nanoparticles and graphene layers prevented the formation of island structures in films, especially at high temperatures. While Ag nanowires and graphene layers formed a uniform, dense three-dimensional network, offering high electrical conductivity. Additionally, an improvement of electrical conductivity by using graphene quantum dots as a graphene component in hybrid inks was observed, which was related to creating new conductive bridges. The highest conductivity of prepared inks varied in the range of 2.67 × 102 S/cm to 4.0 × 104 S/cm. Finally, formulation guidelines were offered to be used for inks by several printing methods.

Magnetite Fe3O4 particles (M) were dispersed in polyvinyl alcohol (PVA) and oriented successfully by applying low external magnetic field. Observed orientation was verified by image analysis using ImageJ software. Crystallinity of the M/PVA samples was examined using DSC, showing a lower crystallinity by addition of particles and higher crystallinity resulting from orientation. Orientation of 0.05 and 0.1 wt% of M particles increased crystallinity of nanocomposites 39 and 57%, respectively. Tensile tests were also measured to examine the mechanical properties of oriented and non-oriented samples. Results show that the mechanical properties of samples including elongation at break and modulus had improved in the direction of oriented particles. Afterward, graphene oxide particles were magnetized [magnetic graphene oxide (MGO)] and dispersed in PVA resulting in improved mechanical properties. PVA/MGO nanocomposites showed better mechanical properties than PVA/M, although no improvement in the crystallinity was observed.

Background Understanding the effects of cardiac diseases on the heart's functionality which is the purpose of many biomedical researches, directly affects the diagnostic and therapeutic methods. Myocardial infarction (MI) is a common complication of cardiac ischemia, however, the impact of MI on the left ventricle (LV) flow patterns has not been widely considered by computational fluid dynamics studies thus far. Methods In this study, we present an insightful numerical method that creates an artificial MI on an image-based fluid-structure interactional model of normal LV to investigate its influence on the flow in comparison with the normal case. Seventeen different models were developed to evaluate the effects of location, percentage, myocardial material properties and dilation size of MI on the LV's performance, area strain, wall displacement, pressure-volume loop, wall shear stress and velocity field. Results The results show that MI considerably changes blood flow features which are fully dependent on MI parameters. For the case of constant MI location, the effect of a decrease of infarcted myocardium stiffness, increase of dilation size and increase of MI percentage are mostly similar. Although the location differences of MI under other constant conditions have similar impact on the ejection fraction, they also lead to dissimilar variations in the LV flow pattern and other indicators. Conclusions The presented model showed a capable computational method for investigating various mechanical MI conditions with respect to cardiac flow pattern. The perspective of this model development seems to be an applicable tool for MI clinical diagnosis and prediction of complications related to MI.

Engineered cementitious composites containing polymeric fibers such as poly(vinyl alcohol) show high tensile ductility and toughness. The aim of the current study was to evaluate the effect of crystallinity degree of poly(vinyl alcohol) fibers on fiber debonding from cementitious matrix in the bending test. In this work, two types of poly(vinyl alcohol) fibers and one grade of polypropylene fiber were separately incorporated in cementitious composites. The chemical structure, surface chemistry, roughness, and microstructure of fibers were examined by Fourier transform infrared, attenuated total reflection, atomic force microscopy, and wide-angle X-ray diffraction tests, respectively. The compression and flexural behaviors of cementitious composites were also assessed. Attenuated total reflection results were indicative of similar surface chemistry for both poly(vinyl alcohol) fibers, while the main difference was observed in the case of degree of crystallinity, which plays an important role in the Poisson’s ratio. Finally, the way in which the degree of crystallinity and Poisson’s ratio of fibers can lead to premature debonding was described and confirmed by scanning electron microscopic images.

A transparent planar electrode from thermally reduced graphene oxide (TRGO) incorporated with a photoconductive thin film of zinc oxide (ZnO) was successfully employed in a visible-blind ultraviolet (UV) photodetector. The TRGO layer was obtained from thermal reduction of drop-cast GO layer at the temperature of 400 °C after which the electrical resistance of layer decreased four orders of magnitude to ~100 Ω. Then a pure and uniform ZnO thin film with the thickness of ~80 nm was sputtered on the TRGO layer. High UV absorption and visible transparency with the average transmittance of 92% in the range of 400–800 nm (T400−800) were obtained for the ZnO thin film. Moreover, the TRGO layer was highly capable in collecting photogenerated electrons from ZnO thin film and efficient transport of charge carriers to the contact electrodes. The ZnO/TRGO device showed an ideal Ohmic behavior and high visible-light transparency with T400−800 = 80%. Furthermore, the results of current–time measurements with cyclic exposure of the device to UV light indicated stable ON/OFF switching states and highly repeatable photoresponse.

There is a common knowledge that the dynamic and structural behavior of polymer chains in the vicinity of nano-fillers is rather different from the bulk. Despite the extensive literature on this topic, this phenomenon is not yet fully understood. Apart from several experimental methods to study it, molecular simulations, in particular molecular dynamics (MD) methods, are good candidates for such study. In other words, MD simulation techniques give us a remarkable ability for mechanistic studies of dynamic and structural properties of polymer chains in nano-scales and they are proved to be highly reliable methods for estimating such properties. Therefore, in this study, we developed a time and spatially-resolved molecular dynamic method by which the structural and dynamic properties of two polymers, i.e., polypropylene (PP) and polyvinyl alcohol (PVA), are studied as a function of distance from graphene (G) and graphene oxide (GO) nano-layers.

The interest in wearable supercapacitors has been flourishing in both the scientific and industrial fields. Here, daily-used polyester fabric (PET) is modified by using an Al-based MOF, namely MIL-53(Al), via a layer-by-layer assembly method at room temperature. Then, reduced graphene oxide is deposited on the PET/MOF surface through dip coating in a graphene oxide suspension, followed by chemical reduction. Ultimately, pyrrole is polymerized on the surface of the PET/MOF/rGO surface by an in situ chemical polymerization process. The obtained composite is used as electrode achieving an areal capacitance of 510 mF cm−2 at a scanning rate of 1 mV s−1 in an aqueous H2SO4 electrolyte. The optimized electrode is employed in a symmetrical solid-state-supercapacitor device, which delivers a volumetric capacitance of 3.5 F cm−3, energy density of 64 μW h cm−3 and power density of 0.6 mW cm−3. The symmetrical device shows a good cycling stability even after 12 months storage in ambient conditions retained 85% of the initial capacitance after 1000 voltammetric cycles.

Creation and control of long-chain branches (LCBs) in coordination polymerization of olefins is an enduring focus of research in both academia and industry. We have recently introduced a tandem catalytic coordinative chain transfer polymerization reaction where upon the concerted function of the polymerization catalyst, the chain transfer agent (CTA), and the displacement catalyst, a highly branched microstructure can be formed. Here we introduce a new tandem catalytic system using Et(Ind)2ZrCl2 as the polymerization catalyst. Despite the optimal reaction temperature for the cooperative function of catalyst components is lower than the ideal temperature for the productivity of the metallocene catalyst, the formation of branches is evident from the decrease and broadening of melting peaks and deviation of rheological properties from characteristic behavior of linear chains in cole–cole plots. Surprisingly, the introduction of the displacement catalyst in CCTP of 1-hexene resulted in low yields and too short polymer chains. Accordingly, we elaborate on the mechanism of this reaction, specifically, we show how the optimal conditions for the (BiPy)2FeEt2 displacement catalyst depend on the monomer type. Namely, the presence of a β–agostic interaction in the bimetallic intermediate formed by the CTA and the displacement catalyst alters the structure of the latter when monomers longer than ethylene are present. This report suggests that our proposed method for the synthesis of branched polyolefins has a great potential for being used in the currently available industrial plants that employ classic metallocene catalysts.

Polymers with carbonyl groups are widely used in metal binding. It is believed that oxygen-containing functional groups have an essential role in the adhesion of polymers to metal surfaces. Here, molecular dynamics simulation has been employed to study oxygen atoms in the vinyl acetate and maleic acid functional groups that have a main role in the adhesion of poly (vinyl chloride-co-vinyl acetate-co-maleic acid) lacquer to aluminum. Based on the results, carbonyl groups had various neighboring bonds that resulted in different positioning and performances of oxygen atoms in the bonding strength. While oxygen atoms of carbonyl bonds in vinyl acetate had a higher tendency for the aluminum surface, oxygen atoms of maleic acid were closer to the aluminum surface, due to the smaller special hindrance of neighboring hydrogen atoms. It led to a difference in the surface concentrations of oxygen among different comonomers. Analyzing the orientation function revealed that the carbonyl bonds of vinyl acetate and maleic acid were oriented near the aluminum surface, as had been previously observed by Kim et al. [1]. The bond orientation and distance from the aluminum surface were found to be the main reasons behind the more effective role of maleic acid in the adhesion to aluminum, compared to vinyl acetate.

Manufacturing proper electrodes for supercapacitors including high capacitance is of great importance for current increased demand for energy storage devices. In this paper, we evaluated metal nanoparticles infused in electrospun carbon nanofibers (ECNF) synthesized by electrospinning, followed by thermal treatment for supercapacitors’ electrode applications. The electrodes were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry. The characterization results indicated that the metal/ECNF samples have fibrous morphology, porous structure with a high specific surface area, including dispersed metal nanoparticles. The effect of embedding various transition metals, such as Co, Ni, and Cu on the electrochemical performance of ECNF has been investigated. The incorporation of Cu into ECNF resulted in the highest specific capacitance. At the scan rate of 5 mV s−1, the specific capacitance of the Cu/ECNF sample was 332 F g−1 while it was 4 F g−1 for the ECNF sample.

In this work, a facile and scalable method to produce cellulose based flexible electrodes is introduced. Composite paper electrodes from recycled paper pulp and graphene oxide (GO) were fabricated by solvent casting at room temperature. Electrical conductivity and surface chemistry of the nanocomposite samples were tuned by chemical reduction of GO. Contact angle measurements showed a change in water droplet angle from 0° to 89° depending on the GO content and degree of reduction. Electrical measurements depicted high electrical conductivity with an ideal Ohmic behavior for the composite paper electrodes. Sheet resistance of the sample containing 4 wt% of reduced GO (rGO) was 1.649 × 103 Ω/□ which is 5 orders of magnitude higher than paper pulp. The obtained sheet resistance for the sample with 16 wt% rGO was remarkably high for cellulose based conductive electrode compared with previously reported data. Moreover, the sample containing only 0.5 wt% of rGO showed 40% higher modulus than the neat recycled paper in tension. The resultant nanocomposite can be introduced as a highly conductive and low cost flexible electrode.

High quality indium tin oxide/polyethylene terephthalate (ITO/PET) electrode with sheet resistance as low as 1.16 Ω/□ and the optical transmittance of 91 % at the wavelength of 600 nm was fabricated. The room-temperature radio frequency (RF) magnetron sputtering technique was used to deposit ITO thin film on PET substrate under low RF power without oxygen flow or post treatment. The remarkable value of 118.5 × 10−3 Ω−1 was achieved for the figure of merit in the 93 nm thick ITO thin film, due to the fine tuning of the sputtering parameters. An entirely Ohmic behavior was recorded for the ITO/PET electrode on the copper contacts suggesting that the product is highly capable for application in optoelectronic devices. The results of field emission scanning electron microscopy and atomic force microscopy demonstrated film consistency with a desired surface morphology giving a Rrms value of 2.073 nm. The elemental, chemical and phase analyses further revealed that the deposited ITO thin film on the PET substrate was pure and amorphous.

Conductive hydrogel nanocomposites containing graphite, graphene oxide (GO), and graphene particles were synthesized by free radical polymerization in aqueous solution. The effect of cross-linker, initiator, graphite, GO, and graphene concentrations on water absorbency and electrical conductivity of hydrogels was investigated. The synthesized composites were then characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The graphene/polyacrylamide hydrogels showed highest conductivity of about 0.2 S cm−1, and specific capacitance of polyacrylamide/graphene hydrogel in H2SO4 solution was found to be 616 F g−1.

Graphene, an outstanding material with remarkable electrical, mechanical and thermal properties, has found tremendous potential in electronic devices. Here we report the direct and irreversible reduction of graphene oxide (GO) ultrathin film (UTF) by application of 30 V bias on GO device under the ambient condition. During the process, an ultrahigh current density flowed through UTF resulting in the Joule-heat generation. The heat effectively removed the oxygen-containing groups from GO and restored graphene layer π-conjugated system reducing the electrical resistance down to ~10.7 Ω. The film also exhibited a linear, symmetric and hysteresis-free current response to the biases in the range of −2 to 2 V. Moreover, the sheet resistance as low as ~125 Ω/□ and optical transmittance of 91 % at 550 nm demonstrated that the reduced GO (rGO) UTF is superior to the conventional transparent electrodes. The rGO transparent conductive film sustained an ultrahigh current density in the order of 107 A cm−2 and showed high current stability in the saturated state, which make it an ideal candidate for transparent electrode applications.

Early stage crystallization kinetics of polypropylene (PP)/clay composites is studied using rheometery. Relaxation modulus of composites is measured at low frequencies near liquid–solid transition. Small amplitude oscillating shear flow is applied at low frequencies to obtain relaxation modulus. Relaxation modulus of polymeric materials at the liquid–solid transition follows [Formula: see text], at long times ( λ < t < ∞), where λ is the time to crossover to a different relaxation regime, s is the gel stiffness, and n is the relaxation exponent. Inverse quenching technique is then employed to retain degree of crystallization while rheological measurements are made. Lower gel time is observed as clay concentration increased, indicating the formation of more nuclei. An improvement to Avrami’s equation is proposed to predict crystallization kinetics for PP/clay composites. There is a good agreement between predicted relative crystallinity values and empirical values.

In this research, an attempt was made to stabilize reduced graphene oxide (rGO) in all pH ranges, incorporating both chitosan (CS) and hydroxyethyl cellulose (HEC) to make a proper drug carrier with suitable stability and drug release behaviour. The stability of rGO-CS-HEC nanohybrid was assessed using field emission scanning electron microscopy (FE-SEM), ultraviolet-visible spectroscopy (UV-Vis) and Zeta potential measurements. Results depicted that the novel synthesized nanohybrid was stable in all pH ranges, due to the utilization of HEC, while without incorporation of this material, the rGO-CS nanohybrid aggregated at neutral and alkaline media, due to the ionic nature of chitosan. In addition, drug loading and release behaviour of folic acid (FA), as a model drug, was investigated to assess the role of chitosan on the release behaviour of FA from the rGO-CS-HEC nanohybrid in comparison with rGO-HEC and rGO-CS nanohybrids. It was proved that the resultant nanohybrid could release nearly 27% more FA than the rGO-HEC nanohybrid and only 9% lower than the rGO-CS nanohybrid during 120h. Moreover, the biocompatibility of the resultant nanohybrid was also checked to introduce the novel rGO-CS-HEC nanohybrid as a suitable candidate for drug delivery application.

Left ventricle (LV) fluid dynamics and the function of its valves have a crucial impact on clinical diagnosis, treatment and prosthesis design. In this paper, we simulated left ventricular flow using 3D computational fluid dynamics (CFD) based on geometrical and deformational information obtained from MRI. Time variant smoothed LV shapes were extracted from MR images. Corresponding deformation data was interpolated using a cubic-spline interpolation. To evaluate valve influence on LV flow, we compared two planar valve models: physiologically corrected gradually opening/closing model and a simple on/off model. Endocardial displacement was applied to fluid boundary using fluid-structure interaction (FSI) approach. Arbitrary Lagrangian-Eulerian (ALE) formulation was used for unsteady incompressible viscous Newtonian blood flow in the fluid domain. Comparison of results for LV flow with two valve models demonstrated a clear distinction between pressure distribution, velocity distribution, vortex formation/growth/vanishing and energy dissipation especially in the filling phase. Consequently, LV flow simulation by ignoring geometrical details of valves׳ model may lead to non-realistic results in some aspects.

A novel fibrous polymer electrolyte membrane was produced based on polymethyl methacrylate/polyacrylonitrile (PMMA/PAN) blend. This was achieved through optimization in the loadings of the two polymers and electrospinning method. Consequently, the effect of PMMA on the ionic conductivity was assessed. A quantitative relationship between ionic conductivity and the important parameters including voltage, solution concentration, and PMMA content was determined. The response surface method (RSM) was employed to obtain the quantitative relationship and to determine the ion conductivity of PAN/PMMA electrospun membrane. Analysis of variance technique was used to study the importance of parameters and their interactions. A regression model was applied to determine the most influential factors on the ionic conductivity and to find the maximum ionic conductivity of the electrolyte membrane as an optimal result. The average fiber diameter was in the range of 206–367 nm, and the membranes were associated with high porosities between 50 and 91 %, and the electrolyte uptakes were in the range of 285–460 %. For all samples, the ionic conductivity of gel polymer electrolytes at 25 °C was above the 1 mS/cm. The ionic conductivity changed with the voltage directly and with the solution concentration inversely. According to the results, the ionic conductivity showed its dependency with the PMMA content, increasing with the PMMA content up to 50 % and smoothly decreasing with PMMA further increases. Some important interactions between the parameters were also detected.

A novel, simple and effective surface passivation technique is introduced to enhance UV spectrum selectivity of ZnO nanoparticles (NPs). The technique which exploits an absorbed layer of dimethylformamide, enables the synthesis and surface passivation of ZnO NPs through a single-step process. Pure ZnO NPs and passivated ones were characterized to evaluate the integrity of passivating layer as well as quality of the final product. Morphological examinations were performed using field-emission scanning and transmission electron microscopies. X-ray diffractometry, energy dispersive X-ray and fourier-transform infrared spectroscopies were employed to analyze the phase and chemical composition of the samples. We also compared optical properties of the surface-passivated and pure ZnO NPs. Photoluminescence measurements revealed a peak value for UV emission at 394 nm and one for violet emission at 412 nm for the passivated and pure samples; respectively. A significant enhancement was observed in the spectrum selectivity and absorption efficiency of the passivated ZnO NPs in the UV range. The passivated NPs exhibited high UV-to-visible rejection ratio and UV-blocking capacity which provide a promising candidate for visible-blind UV photodetectors and UV shielding applications.

Poly(ethylene tetrasulfide) (PSP) is synthesized via interfacial polycondensation of 1,2 dichloroethane and sodium tetrasulfide, in the presence of graphene oxide (GO). This process resulted in homogeneously dispersed PSP/GO nanocomposites. Nanocomposites of 0.3 and 0.5 wt% of GO are synthesized and their morphology, chemical characteristics behavior are studied employing field emission scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques. Thermal characterization of composites is performed by differential scanning calorimetry and thermogravimetry analysis. Results indicate that the addition of only small amounts (0.5 wt%) of well-dispersed GO can increase the melting point more than 16°C resulting in better thermal properties for the composite. The solubility of nanocomposite is also studied and results show that the solubility depends on solvent concentration in addition to reinforcement (GO) deals.