Search

Flexible metal-organic materials (FMOMs) with stepped isotherms can offer enhanced working capacity in storage applications such as adsorbed natural gas (ANG) storage. Unfortunately, whereas >1000 FMOMs are known, only a handful exhibit methane uptake of >150 cm 3 /cm 3 at 65 atm and 298 K, conditions relevant to ANG. Here, we report a double-walled 2-fold interpenetrated diamondoid ( dia ) network, X-dia-6-Ni, [Ni 2 L 4 (μ-H 2 O)] n , comprising a new azo linker ligand, L - ( L - = ( E )-3-(pyridin-4-yldiazenyl)benzoate) and 8-connected dinuclear molecular building blocks. X-dia-6-Ni exhibited gas (CO 2 , N 2 , CH 4 ) and liquid (C8 hydrocarbons)-induced reversible transformations between its activated narrow-pore β phase and γ , a large-pore phase with ca . 33% increase in unit cell volume. Single-crystal X-ray diffraction (SCXRD) studies of the as-synthesized phase α , β , and γ revealed that structural transformations were enabled by twisting of the azo moiety and/or deformation of the MBB. Further insight into these transformations was gained from variable temperature powder XRD and in situ variable pressure powder XRD. Low-temperature N 2 and CO 2 sorption revealed stepped Type F-II isotherms with saturation uptakes of 422 and 401 cm 3 /g, respectively. X-dia-6-Ni exhibited uptake of 200 cm 3 /cm 3 (65 atm, 298 K) and a high CH 4 working capacity of 166 cm 3 /cm 3 (5-65 bar, 298 K, 33 cycles), the third highest value yet reported for an FMOM and the highest value for an FMOM with a Type F-II isotherm.

Hybrid ultramicroporous materials (HUMs), metal-organic platforms that incorporate inorganic pillars, are a promising class of porous solids. A key area of interest for such materials is gas separation, where HUMs have already established benchmark performances. Thanks to their ready compositional modularity, we report the design and synthesis of a new HUM, GEFSIX-21-Cu , incorporating the ligand pypz (4-(3,5-dimethyl-1 H -pyrazol-4-yl)pyridine, 21 ) and GeF 6 2- pillaring anions. GEFSIX-21-Cu delivers on two fronts: first, it displays an exceptionally high C 2 H 2 adsorption capacity (≥5 mmol g -1 ) which is paired with low uptake of CO 2 (<2 mmol g -1 ), and, second, a low enthalpy of adsorption for C 2 H 2 ( ca . 32 kJ mol -1 ). This combination is rarely seen in the C 2 H 2 selective physisorbents reported thus far, and not observed in related isostructural HUMs featuring pypz and other pillaring anions. Dynamic column breakthrough experiments for 1:1 and 2:1 C 2 H 2 /CO 2 mixtures revealed GEFSIX-21-Cu to selectively separate C 2 H 2 from CO 2 , yielding ≥99.99% CO 2 effluent purities. Temperature-programmed desorption experiments revealed full sorbent regeneration in <35 min at 60 °C, reinforcing HUMs as potentially technologically relevant materials for strategic gas separations.

We report that linker ligand substitution involving just one atom induces a shape-memory effect in a flexible coordination network. Specifically, whereas SIFSIX-23-Cu, [Cu(SiF 6 )(L) 2 ] n , (L=1,4-bis(1-imidazolyl)benzene, SiF 6 2- =SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX-23-Cu N , [Cu(SiF 6 )(L N ) 2 ] n (L N =2,5-bis(1-imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO 2 . As-synthesized SIFSIX-23-Cu N , α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N 2 (77 K), rather it reverted to α induced by CO 2 at 195, 273 and 298 K. CO 2 desorption resulted in α', a shape-memory phase which subsequently exhibited type-I isotherms for N 2 (77 K) and CO 2 as well as strong performance for separation of CO 2 /N 2 (15/85) at 298 K and 1 bar driven by strong binding (Q st =45-51 kJ/mol) and excellent CO 2 /N 2 selectivity (up to 700). Interestingly, α' reverted to β after re-solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX-23-Cu N ., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu , a new variant of a previously reported ultramicroporous square lattice, sql , topology material, sql-SIFSIX-bpe-Zn , can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA ( AA ) and sql-NbOFFIVE-bpe-Cu-AB ( AB ), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA ( AA ) is isostructural with sql-SIFSIX-bpe-Zn , each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB ( AB ) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C 3 H 4 /C 3 H 6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C 3 H 4 /C 3 H 6 selectivity (270) and a new benchmark for productivity (118 mmol g -1 ) of polymer grade C 3 H 6 (purity > 99.99%) from a 1:99 C 3 H 4 /C 3 H 6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot" for C 3 H 4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C 3 H 4 and C 3 H 6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.

Coordination networks (CNs) that undergo gas-induced transformation from closed (nonporous) to open (porous) structures are of potential utility in gas storage applications, but their development is hindered by limited control over their switching mechanisms and pressures. In this work, we report two CNs, [Co(bimpy)(bdc)] n ( X-dia-4-Co ) and [Co(bimbz)(bdc)] n ( X-dia-5-Co ) (H 2 bdc = 1,4-benzendicarboxylic acid; bimpy = 2,5-bis(1H-imidazole-1-yl)pyridine; bimbz = 1,4-bis(1H-imidazole-1-yl)benzene), that both undergo transformation from closed to isostructural open phases involving at least a 27% increase in cell volume. Although X-dia-4-Co and X-dia-5-Co only differ from one another by one atom in their N -donor linkers (bimpy = pyridine, and bimbz = benzene), this results in different pore chemistry and switching mechanisms. Specifically, X-dia-4-Co exhibited a gradual phase transformation with a steady increase in the uptake when exposed to CO 2 , whereas X-dia-5-Co exhibited a sharp step (type F-IV isotherm) at P / P 0 ≈ 0.008 or P ≈ 3 bar (195 or 298 K, respectively). Single-crystal X-ray diffraction, in situ powder XRD, in situ IR, and modeling (density functional theory calculations, and canonical Monte Carlo simulations) studies provide insights into the nature of the switching mechanisms and enable attribution of pronounced differences in sorption properties to the changed pore chemistry.

In this study, dimensional, conformational and dynamic behaviors of a short-chain branched styrene/1-octene copolymer chain with different 1-octene percentages, i.e., 0, 2, 4 and 6%, in toluene are investigated at the temperature of 298.15 K via molecular dynamics simulation. The chain dimensions and flexibility in the solvent are evaluated by calculating the radius of gyration (R g ), end-to-end distance (0 >), surface area (A ch ), and volume (V ch ) of the copolymer chain. The mean square displacement (MSD) and diffusivity coefficient for each copolymer chain are measured to determine its dynamic behavior and mobility in aromatic media. To consider the effect of increasing the 1-octene co-monomer percentage on the copolymer chain affinity to the solvent molecules, the interaction energy (E int ) and Flory-Huggins (FH) interaction parameter are calculated for each equilibrated solution model. The simulation results indicate that the co-monomer level increment in the copolymer structure reduces the chain R g amount and its interaction with the solvent. The 0 > of the chain increases up to 4% co-monomer content, while further co-monomer content decreases the 0 > value. Additionally, the viscosity of the equilibrated dilute solutions is calculated via non-equilibrium molecular dynamics simulation (NEMD). Moreover, the steric hindrance of the copolymers and the solvent molecules capturing in the dilute solution is determined via radial distribution function (RDF) analysis. Helmholtz free energy and the system entropy changes are calculated to evaluate the tendency of the copolymer to the solvent molecules and its dilute solution irregularity, respectively. Graphical abstract The figure shows the variations trend of the poly(styrene-co-1-octene) chain dimensions in toluene aromatic solvent by increasing the 1-octene content (x), after the equilibration state. Red and blue colors represent the carbon atoms of the copolymer chain backbone and 1-octene side chains, respectively. The styrene rings and the hydrogen atoms of the chains were removed for better view.

The self-assembly behaviour of dual-responsive block copolymers and their ability to solubilize the anticancer drug doxorubicin (DOX) has been investigated using all-atom molecular dynamics (MD) simulations, MARTINI coarse-grained (CG) force field simulation and Scheutjens-Fleer self-consistent field (SCF) computations. These diblock copolymers, composed of poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone} (PMEEECL) and poly(β-amino ester) (PAE) are dual-responsive: the PMEEECL block is thermoresponsive (becomes insoluble above a certain temperature), while the PAE block is pH-responsive (becomes soluble below a certain pH). Three MEEECL 20 -AE M compositions with M = 5, 10, and 15, have been studied. All-atom MD simulations have been performed to calculate the coil-to-globule transition temperature ( T cg ) of these copolymers and finding appropriate CG mapping for both PMEEECL-PAE and DOX. The output of the MARTINI CG simulations is in agreement with SCF predictions. The results show that DOX is solubilized with high efficiency (75-80%) at different concentrations inside the PMEEECL-PAE micelles, although, interestingly, the loading efficiency is reduced by increasing the drug concentration. The non-bonded interaction energy and the RDF between DOX and water beads confirm this result. Finally, MD simulations and SCF computations reveal that the responsive behaviour of PMEEECL-PAE self-assembled structures take place at temperature and pH ranges appropriate for drug delivery., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Molecular characteristics of an atactic polystyrene (aPS) chain with different lengths in a theta solvent, cyclohexane at 307.65 K, were studied via molecular dynamics (MD) simulation. The interaction energy of the aPS dilute solution models and Flory-Huggins (FH) interaction parameter were calculated to investigate the effect of the chain molecular weight on its compatibility with the solvent molecules. The simulation results illustrated that increasing the chain length increased the interactions between the chain and the solvent molecules. The chain dimensions via calculating the radius of gyration (R g ) and end-to-end distance, 0 >, were measured. Mean square displacement (MSD) and diffusivity coefficient of the chains were calculated to determine their dynamic behavior. The results exhibited that two factors of the chain movability and size were important for the diffusion in oligomeric state. Additionally, viscosity of the resultant dilute solutions was calculated via nonequilibrium molecular dynamics simulation (NEMD). Moreover, the steric hindrance of the chains was determined by radial distribution function (RDF) analysis. The calculated characteristics of the chain and solution viscosity results showed a good agreement with experimental published works. Measurement of the potential field of cyclohexane-cyclohexane and aPS-cyclohexane pairs was also based on their potential field via quantum chemical calculations to determine the special orientation of the solvent molecules to each other and to the polymer segments, respectively. Graphical abstract (a) The equilibrated dilute solution model of polystyrene in cyclohexane at theta temperature (the red and yellow balls represent carbon and hydrogen atoms, respectively. The cyclohexane molecules are illustrated in line style in the box), (b) the electrostatic potential field around an optimized structure containing two cyclohexane molecules, and (c) around the sole cyclohexane molecule and polystyrene with two repeating units (carbon and hydrogen atoms are represented in green and yellow, respectively).

According to the critical role of drug delivery in the treatment of diseases of the central nervous system (CNS), the selection of a suitable carrier plays an important role in the greater effectiveness of drugs. Due to good biocompatibility, biodegradability and low toxicity of polymeric nanoparticles, especially poly(n-butylcyanoacrylate) (PBCA) and Chitosan, these nanoparticles are considered as efficient carriers in drug delivery to the brain. In order to investigate the compatibility of these two polymers with different degrees of polymerization versus a Tacrine unit as the most well known drug for the treatment of Alzheimer's disease, molecular dynamics simulation (MD) is used as a principal tool for studying molecular systems. Interaction energy of the polymer/Tacrine systems, the radius of gyration of the Chitosan and PBCA during the simulation time, solubility and Flory-Huggins interaction parameters has been calculated. According to the results, the Tacrine molecule exhibited higher compatibility with PBCA than Chitosan. Moreover, the interaction between the Tacrine molecules and PBCA nanoparticles became stronger by increasing the length of polymer chain while it was not observed as a regular trend for Chitosan/Tacrine systems. By using these MD simulations, it is possible to find the most appropriate polymer as an efficient drug carrier. We note that the methodology applied here for modeling the polymer/Tacrine system is not restricted to the specific formulations of Tacrine and Chitosan (or PBCA) in the current work and can be extended to various other traditional or new drugs and different polymer drug carriers., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this study, interfacial adhesion between functionalized polyethylene (PE) surfaces and graphene were examined using molecular simulation. Various functional groups including amino, carboxy, hydroxy, cyano, isocyanato, oxo, and ethylamino were used to cover the PE surface with surface densities of 0.48, 1.30, and 4.84 groups per nm(2). The interfacial adhesion between the modified PE surfaces and the graphene was quantified via calculation of work of separation (Wsep), the amount of the required work to separate two surfaces without occurring any relaxation and diffusion phenomena. Insertion of the functional groups on the PE surface decreased the amount of Wsep, except for the oxo, amino, and higher densities of the carboxy groups. Increasing the surface group density enhanced the adhesion due to decreasing the surface atomic roughness and increasing the atomic density at the interface. In addition, the effect of surface group rearrangement was investigated via calculation of the work of adhesion (Wadh) while sufficient time had been devoted to relax the interface. The surface reorganization during the relaxation process significantly enhanced adhesion due to eliminating the surface roughness and increasing the surface atomic density.

Currently, clear guidance is not available for determining the minimum practical chain lengths needed for achieving reasonable convergence when performing atomistic simulations of common synthetic polymers. Here, we analyze a collection of polymers, including polypropylene (PP), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyethylene glycol (PEG), poly(methyl methacrylate) (PMMA), polystyrene (PS), and polyvinyl chloride (PVC), with chain lengths varying from 5 to 240 repeat units. We exclusively focus on solvated polymer systems, and we report the convergence of several characteristic properties, such as radial distribution functions (RDFs), surface area per repeat unit (SASA/N), ratio of mean squared end-to-end distance to mean squared radius of gyration ($\displaystyle{{\left\langle {R^2} \right\rangle } \over {\left\langle {R_g^2 } \right\rangle }}$ 〈 R 2 〉 〈 R g 2 〉 ), and surface electrostatic potential distributions. Based on these data, we propose a general relationship for identifying minimum practical chain lengths for performing atomistic simulations of solvated linear synthetic polymers, which is based on the SASA/N. [ABSTRACT FROM AUTHOR]

We have successfully synthesised silver quantum dots (Ag QDs) via chemical method. We have studied Ag QDs doped 4-(trans-4-n hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) LC hybrid system and their associated structural and optoelectronic properties using both experimental and theoretical methods. The QDs with sizes 4.27 nm−9.56 nm self-assemble to form nano-micro scale hierarchical structures. Theoretical NMR study has been performed using three different methods HF, B3LYP, and wB97XD for pure and Ag NPs doped LC system. NMR data greatly helps us to explore the phenomenological description of the hybrid system by giving us molecular scale insights. Optical microscope, RAMAN, UV, FTIR, HR-XRD, FESEM-EDX, and Fluorescence data confirm the structural and physio-chemical properties of QDs, LC molecules and as well as their hybrid system. We use a nanoscale predictive model to estimate the effective size to which the bandgap value of Ag QDs in a hybrid system corresponds. The bandgap value of pure Ag QDs is found to be 5.32 eV, whereas upon doping these Ag QDs in LC media, their bandgap falls to a value of 4.08 eV. The estimated size (i.e. corresponding to effective confinement) using a hexahedral or octahedral-shaped particle model comes out to be ~15 nm. We successfully synthesized Ag QDs using chemical co-precipitation method. Our FTIR, Raman, UV, FL, XRD data confirm for their crystalline nature and purity. We have doped it in 6CHBT LC media and obtained nano-micro scale clusters. The Ag QDs doped 6CHBT LC hybrid system and their associated chemical and optoelectronic properties have not been studied experimentally and theoretically well. The molecular scale insight for the variations of the optoelectronic properties of the QDs and LC hybrid system is scarcely available in published report. QD sizes 4.2768 nm–9.5662 nm self-assembled to form nano-micro scale hierarchical structures. The smaller size NPs can easily align with the director axis of the LC molecules, whereas the larger ones self assemble and agglomerate with each other to form bigger clusters of Ag NPs. The sizes of the clusters in latter case extend up to a few tens of microns. The hierarchical arrangement of smaller NPs is supposed to be energetically more favourable and form a composite matrix, i.e. LC molecules allow relatively smaller size QDs to form hybrid structure inside LC matrix. We use nanoscale predictive model to estimate the effective size to which the bandgap value of Ag QDs in hybrid system corresponds to. The bandgap value of pure Ag QDs is found to be 5.32 eV, whereas upon doping these Ag QDs in LC media, their bandgap fall to a value of 4.08 eV. The estimated size (i.e. corresponding to effective confinement) using hexahedral- or octahedral-shaped particle model is ~15 nm. We assume that the QDs in LC matrix may arrange themselves in hexahedral or octahedral shape. To some extent, we could narrow down our inferences as direct evidence by imaging at nanoscale does not seem possible due to limitations with imaging soft materials at nanoscales. In order to get molecular scale insight to explore the phenomenon, we have performed NMR characterizations both experimentally and theoretically and compared the two. Theoretical NMR study is performed using three different methods HF, B3LYP, and wB97XD for pure and Ag NPs doped LC system. Variations in chemical shift are presented in greater details. Experimentally and theoretically obtained the NMR results have been successfully correlated with the findings. Presence of sigma hole is observed in the molecular electrostatic potential (MEP) surface of Ag NPs doped LC system. We have highlighted its importance. We have successfully verified the theoretical outcomes with experimental findings. [ABSTRACT FROM AUTHOR]

Neurodegenerative diseases (NDDs) have been increasing in incidence in recent years and are now widespread worldwide. Neuronal death is defined as the progressive loss of neuronal structure or function which is closely associated with NDDs and represents the intrinsic features of such disorders. Amyotrophic lateral sclerosis, frontotemporal dementia, Alzheimer's, Parkinson's, and Huntington's diseases (AD, PD, and HD, respectively) are considered neurodegenerative diseases that affect a large number of people worldwide. Despite the testing of various drugs, there is currently no available therapy that can remedy or effectively slow the progression of these diseases. Nanomedicine has the potential to revolutionize drug delivery for the management of NDDs. The use of nanoparticles (NPs) has recently been developed to improve drug delivery efficiency and is currently subjected to extensive studies. Nanoengineered particles, known as nanodrugs, can cross the blood-brain barrier while also being less invasive compared to the most treatment strategies in use. Polymeric, magnetic, carbonic, and inorganic NPs are examples of NPs that have been developed to improve drug delivery efficiency. Primary research studies using NPs to cure AD are promising, but thorough research is needed to introduce these approaches to clinical use. In the present review, we discussed the role of metal-based NPs, polymeric nanogels, nanocarrier systems such as liposomes, solid lipid NPs, polymeric NPs, exosomes, quantum dots, dendrimers, polymersomes, carbon nanotubes, and nanofibers and surfactant-based systems for the therapy of neurodegenerative diseases. In addition, we highlighted nanoformulations such as N-butyl cyanoacrylate, poly(butyl cyanoacrylate), D-penicillamine, citrate-coated peptide, magnetic iron oxide, chitosan (CS), lipoprotein, ceria, silica, metallic nanoparticles, cholinesterase inhibitors, an acetylcholinesterase inhibitors, metal chelators, anti-amyloid, protein, and peptide-loaded NPs for the treatment of AD., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The molecular dynamics simulations based study of graphene (Gr) reinforced polymer nanocomposite (PNC) is a very intense research field due to the enormous range of possible applications involving such materials. Current review focuses on the reinforcing mechanisms behind the enhancement of the mechanical, thermal, and tribological properties of Gr-based PNC based on molecular dynamics (MD) simulations. It also reviews the capabilities of MD simulations to reproduce the experimentally measured materials properties and behaviour of Gr-based PNC. This review-based investigation summarizes the current literature of the MD simulation studies as well as comparisons for the tribo-thermo-mechanical properties of Gr-based PNC and identification of the suitable simulation protocols for model development, characterization, and mechanism analysis. The careful review of published MD simulation-based articles indicates that two important factors help to reproduce the experimentally measured materials properties and behaviour of Gr-based PNC. They are mainly (a) simulation models (material used for reinforcement, e.g. Gr and Gr derivatives) development and (b) simulation run parameters. In this review, details about those factors have been discussed keeping major consideration of Gr effect (e.g. shape or length, orientation, clustering, weight fraction, different layer, functionalization, and defective condition). Finally potential applications, current challenges and future prospects are discussed which can be useful to the research community. [ABSTRACT FROM AUTHOR]

Nanoscale preparations, such as nanoparticles, micelles, and liposomes, are increasingly recognized in pharmaceutical technology for their high capability in tailoring the pharmacokinetics of the encapsulated drug within the body. These preparations have great potential in extending drug half-life, reducing dosing frequency, mitigating drug side effects, and enhancing drug efficacy. Consequently, nanoscale preparations offer promising prospects for the treatment of metabolic disorders, malignant tumors, and various chronic diseases. Nevertheless, the complete clinical potential of nanoscale preparations remains untapped due to the challenges associated with low drug loading degrees and insufficient control over drug release. In this review, we comprehensively summarize the vital role of intermolecular interactions in enhancing encapsulation and controlling drug release within nanoscale delivery systems. Our analysis critically evaluates the characteristics of common intermolecular interactions and elucidates the techniques employed to assess them. Moreover, we highlight the significant potential of intermolecular interactions in clinical translation, particularly in the screening and optimization of preparation prescriptions. By attaining a deeper understanding of intermolecular interaction properties and mechanisms, we can adopt a more rational approach to designing drug carriers, leading to substantial advancements in the application and clinical transformation of nanoscale preparations. Moving forward, continued research in this field offers exciting prospects for unlocking the full clinical potential of nanoscale preparations and revolutionizing the field of drug delivery., (© 2024. Controlled Release Society.)

Colloidal particles constitute a substantial fraction of organic matter in the global ocean and an abundant component of the organic matter interacting with bacterial surfaces. Using E. coli ribosomes as model colloidal particles, we applied high-resolution atomic force microscopy to probe bacterial surface interactions with organic colloids to investigate particle attachment and relevant surface features. We observed the formation of ribosome films associating with marine bacteria isolates and natural seawater assemblages, and that bacteria readily utilized the added ribosomes as growth substrate. In exposure experiments ribosomes directly attached onto bacterial surfaces as 40–200 nm clusters and patches of individual particles. We found that certain bacterial cells expressed surface corrugations that range from 50–100 nm in size, and 20 nm deep. Furthermore, our AFM studies revealed surface pits in select bacteria that range between 50–300 nm in width, and 10–50 nm in depth. Our findings suggest novel adaptive strategies of pelagic marine bacteria for colloid capture and utilization as nutrients, as well as storage as nanoscale hotspots of DOM. [ABSTRACT FROM AUTHOR]

The epoxy-based nanocomposites are widely used in the aerospace field, which experience harsh conditions with extremely low and high temperatures. The temperature dependence of the properties of epoxy-based nanocomposites in a wide range of temperatures is of great importance for their application. In this work, we used the molecular dynamics (MD) simulation and experimental methods to comprehensively study the temperature dependence of epoxy-based nanocomposites. Three kinds of nanofillers, prepared by grafting three epoxy monomers with different functionality degrees to graphene oxide (GO), were used. The dynamic behavior, interfacial properties and mechanical properties of the nanocomposites in a wide range of temperatures were investigated by MD simulation. Simulation results showed that as temperature decreased from 600 to 4 K, all the nanocomposites exhibited decreased molecular mobility, increased interfacial interaction energy and increased Young's modulus. The tensile properties of the nanocomposites at room temperature (RT), liquid nitrogen temperature (LNT) and liquid helium temperature (LHeT) were also experimentally measured, which agreed well with the simulation results. The tensile strength of nanocomposites increased at LNT compared to that at RT, and then decreased at LHeT. Furthermore, the toughening mechanisms of EFGO to epoxy resin at different temperatures were discussed. The results are expected to provide a new insight into the design and preparation of nanocomposites applied at various temperatures. [ABSTRACT FROM AUTHOR]

Quantitative structure–property/activity relationships (QSPRs/QSARs) are a component of modern natural science. The system of self-consistent models is a specific approach to build up QSPR/QSAR. A group of models of refractive index for different distributions in training and test sets is compared. This comparison is a basis to formulate the system of self-consistent models. The so-called index of ideality of correlation (IIC) has been used to improve the predictive potential of models of the refractive index of different polymers (n = 255). The predictive potential of the suggested models is high since the average value of the determination coefficient for the validation set is 0.885. In addition, the system of self-consistent models may be applied as a tool to assess the predictive potential of an arbitrary QSPR-approach. The statistical characteristics of the best model are the following: n = 57, R2 = 0.7764, RMSE = 0.039 (active training set) and n = 57, R2 = 0.9028, RMSE = 0.019 (validation set). [ABSTRACT FROM AUTHOR]

The major challenge associated with the treatment of neurological disorders is the inefficiency of drugs to enter the Central Nervous System (CNS). Polymer-drug conjugates are now being tailored to overcome this hindrance associated with conventional drugs. The study aimed at developing polymer hybrid nasal nanocomposite for enhanced delivery of Centella to the CNS. Thiolated chitosan was complexed with Centella to form a composite using EDAC hydrochloride. The composite was characterized by FTIR, XRD, NMR, and MS. Further, this composite was converted into a nanoformulation by the ionic-gelation method, characterized, and subjected to ex vivo permeation studies. Additionally, MTT assay was performed using Human Uumbilical cord Vein Endothelial Cells (HUVECs) mimicking Blood–Brain Barrier (BBB) to establish the safety of nanocomposite. The targeting efficacy was predicted by molecular docking studies against receptors associated with BBB. The FTIR, XRD, NMR, and MS studies confirmed the chemical conjugation of thiolated chitosan with Centella. Nanocomposite characterization through SEM, AFM, and DLS confirmed the size and stability of the developed nanocomposite having a zeta potential of − 14.5 mV and PDI of 0.260. The nanocomposite showed no signs of nasal ciliotoxicity and good permeation of 89.44 ± 1.75% (mean ± SD, n = 3) at 8 h across the nasal mucosa. MTT assay showed that the nanocomposite had lesser toxicity compared to the free drug (IC50 of Centella—269.1 μg/mL and IC50 of CTC nanocomposite—485.375 μg/mL). The affinity of polymer to the BBB receptors as proved by docking studies suggests the ability of polymer-based nanocomposite to concentrate in the brain post nasal administration. [ABSTRACT FROM AUTHOR]

Background: Xylanase, an important accessory enzyme that acts in synergy with cellulase, is widely used to degrade lignocellulosic biomass. Thermostable enzymes with good catalytic activity at lower temperatures have great potential for future applications in the feed and fuel industries, which have distinct demands; however, the potential of the enzymes is yet to be researched. Results: In this study, a structure-based semi-rational design strategy was applied to enhance the low-temperature catalytic performance of Bispora sp. MEY-1 XYL10C_∆N wild-type (WT). Screening and comparisons were performed for the WT and mutant strains. Compared to the WT, the mutant M53S/F54L/N207G exhibited higher specific activity (2.9-fold; 2090 vs. 710 U/mg) and catalytic efficiency (2.8-fold; 1530 vs. 550 mL/s mg) at 40 °C, and also showed higher thermostability (the melting temperature and temperature of 50% activity loss after 30 min treatment increased by 7.7 °C and 3.5 °C, respectively). Compared with the cellulase-only treatment, combined treatment with M53S/F54L/N207G and cellulase increased the reducing sugar contents from corn stalk, wheat bran, and corn cob by 1.6-, 1.2-, and 1.4-folds, with 1.9, 1.2, and 1.6 as the highest degrees of synergy, respectively. Conclusions: This study provides useful insights into the underlying mechanism and methods of xylanase modification for industrial utilization. We identified loop2 as a key functional area affecting the low-temperature catalytic efficiency of GH10 xylanase. The thermostable mutant M53S/F54L/N207G was selected for the highest low-temperature catalytic efficiency and reducing sugar yield in synergy with cellulase in the degradation of different types of lignocellulosic biomass. Highlights: Key sites were proved to promote low-temperature catalytic efficiency of xylanase. Thermostable mutant with improved catalytic efficiency at 40 °C was obtained. Synergistic hydrolysis was dramatically improved between the mutant and cellulase. Agricultural wastes were converted into fermentable sugars by enzymolysis. [ABSTRACT FROM AUTHOR]

Recent membrane research has focused on constructing physicochemically stable membranes with high transfer properties above the Robson curve. Polymers blending, cross-linking polymers, and mixed matrix membranes (MMM) have been used to increase membranes performance at different temperatures and pressures. This study aims to compute the morphological and transfer properties of hybrid membranes (Pebax/MIL-53 and Pebax/NH2-MIL-53), blend membranes (Pebax/Cellulose Acetate), and mixed matrix membranes (Pebax/Cellulose Acetate/MIL-53 and Pebax/Cellulose Acetate/NH2-MIL-53), using molecular dynamics (MD) and Monte Carlo (MC) methods via Material Studio software (MS) 2017. The calculated solubility parameter for Pebax, cellulose acetate, and Pebax/cellulose acetate blend were, 19.917 (J/cm3)0.5, 18.174 (J/cm3)0.5, and 18.207 (J/cm3)0.5, respectively. Achieving the same glass transition temperature (Tg) in the Pebax/cellulose acetate blend indicates the proper miscibility of the two polymers. Improving the morphological performance properties of the MMMs by adding MIL-53 and NH2-MIL-53 particles to the Pebax-CA structure was evident in the simulation results. Moreover, the transfer properties performance of the MMMs were improved due to the high compatibility of MOF particles with polymer blends. Furthermore, MIL-53 with the NH2 amine functional group improved the transfer properties of CO2 gas in MMMs due to amino groups' presence and more excellent compatibility due to hydrogen formation bonds to Pebax polymer chain. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) is commonly used thermoplastic polymer, mostly formed via chain-growth polymerisation. Carbon nanotube (CNT) is a remarkable nanofiller for polymers having high electrical conductivity, tensile strength, modulus, and thermal conductivity. The aim of this overview is to present design, synthesis strategies, characteristics, and applications of polypropylene/carbon nanotube (PP/CNT)-based nanomaterials. Combination of PP with CNT has consequence applications in fuel cell components, radiation shielding, strain sensing, and non-flammable materials. Surface treatment of nanoparticles may further enhance interfacial interactions to progress comprehensive features of PP/CNT nanocomposites. Furthermore, it discusses challenges and opportunities to facilitate the production of next-generation high-performance PP/CNT nanocomposite. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease clinically characterized by progressive loss of memory, impairment cognitive function, and neuropsychiatric and behavior dysfunction. The molecular pathology of the disease is characterized with extracellular accumulation of amyloid β plaques and neurofibrillary tangles composed of hyperphosphorylated Tau. Even with crescent number of AD patients worldwide, the current treatment approved does not alter the course of the disease but rather controls the symptoms. In addition to this, also present poor solubility and low bioavailability. Therefore, several studies have been exploring new delivery systems to efficiently deliver those drugs and enhance biological activity. Among them, nanoparticulated systems have demonstrated great potential as a drug delivery system in neurodegenerative disease. In this review, we will reflect on the current progress of nanoparticulated systems with an overall particle size ranging from 2 up to 200 nm and potential to deliver AD drugs for AD treatment. [ABSTRACT FROM AUTHOR]

Drug delivery plays a substantial role in a more effective treatment of diseases of the central nervous system; therefore, the selection of an appropriate drug carrier system is very important to enhance the effectiveness of drugs. Due to the effect of surfactant on improvement of polymer performance in drug-carrying systems, the present study was devoted to investigating the influence of Polysorbate 80 (Pst80) surfactant on poly(n-butylcyanoacrylate)(PBCA)/Tacrine and Chitosan/Tacrine drug-carrying systems from molecular point of view. Interaction energy, structural characterization, Flory–Huggins interaction parameter, and solvation free energy were investigated for both systems by employing molecular dynamics simulations. According to the interaction energy and Flory–Huggins parameter results, Pst80 can be a more suitable choice for targeted releasing of drug in PBCA/Tacrine system compared with Chitosan/Tacrine system because Pst80 firmly surrounded the drug carrier PBCA and Tacrine. Additionally, the solvation free energy results demonstrated more solubility of PBCA/Pst80/Tacrine in water medium compared with that of Chitosan/Pst80/Tacrine. By consideration on different solvation free energy contributions, it was concluded that using a polymer with both hydrophilic and hydrophobic parts, presence of functional groups with heavy atoms on both polymer and surfactant and similarity in chemical nature of hydrophobic parts of both polymer and surfactant can be useful approaches to reduce the total solvation free energy. Preparation of an appropriate solubility of polymer/drug in water/surfactant medium is essential to enhance drug delivery system efficiency and reduce waste of drug in human body, which can be achieved by designing a drug-carrying system with the minimum solvation free energy. This study confirms the significant role of molecular dynamics simulation for a detailed study of polymer/surfactant/dug systems and clarifies its effective role for designing novel drug delivery systems, along with saving time and cost. [ABSTRACT FROM AUTHOR]

In the recent work, we have used the density functional theory (DFT) and the molecular dynamics (MD) simulation methods to investigate the adsorption behavior of paracetamol and phenacetin molecules on the boron nitride nanotubes (BNNTs) in the aqueous phase. In this research, several armchair (n,n) BNNTs, where n = 5, 6, and 7 have been used. Two different interactions, including interaction of paracetamol and phenacetin molecules with outer and inner surfaces of BNNTs were studied. The results show that both paracetamol and phenacetin molecules are not adsorbed inside of (5,5) BNNT and are desorbed. It is found that the most stable adsorption corresponds to (6,6) BNNT, when the drug molecule is located inside of the nanotube. The strongest interaction corresponds to adsorption of phenacetin molecule inside of (6,6) BNNT. [ABSTRACT FROM AUTHOR]

Anomalous proximity effects have been observed in adhesive systems ranging from proteins, bacteria, and gecko feet suspended over semiconductor surfaces to interfaces between graphene and different substrate materials. In the latter case, long-range forces are evidenced by measurements of non-vanishing stress that extends up to micrometer separations between graphene and the substrate. State-of-the-art models to describe adhesive properties are unable to explain these experimental observations, instead underestimating the measured stress distance range by 2–3 orders of magnitude. Here, we develop an analytical and numerical variational approach that combines continuum mechanics and elasticity with quantum many-body treatment of van der Waals dispersion interactions. A full relaxation of the coupled adsorbate/substrate geometry leads us to conclude that wavelike atomic deformation is largely responsible for the observed long-range proximity effect. The correct description of this seemingly general phenomenon for thin deformable membranes requires a direct coupling between quantum and continuum mechanics. The unexpectedly long-ranged interface stress observed in recent delamination experiments is yet to be clarified. Here, the authors develop an analytical approach to show the wavelike atomic deformation as the origin for the observed ultra long-range stress in delamination of graphene from various substrates. [ABSTRACT FROM AUTHOR]

The interface of graphene/epoxy was studied using molecular dynamics simulations by calculating the work of separation and traction-separation responses in the normal mode. The influence of functionalization of the graphene layers on the traction-separation behaviour was also examined by grafting hydroxyl, carboxyl, and carbonyl groups. It is shown that the magnitude of the maximum traction is clearly larger for functionalized graphene/epoxy systems as compared to pristine graphene. The work of adhesion also shows a clear difference in the interface behaviour of functionalized graphene/epoxy and pristine/epoxy systems with the presence of functional groups generating higher values of work of separation. [ABSTRACT FROM AUTHOR]

Hydroxyl functionalized h-BN nanosheets (BNNS) are potential applicant for reinforcing polymer-based nanocomposites and developing nanomembranes for ion separation. So far, the literature is almost mute on the mechanical and fracture behaviour of hydroxyl functionalized BNNS. In this article, molecular dynamics-based simulations were performed to investigate the effect of different hydroxyl regimes on the fracture and mechanical behaviour of BNNS. Reactive force field based interatomic potential was used to capture the atomistic interaction in pristine and hydroxyl functionalized BNNS. In order to capture the dynamics of mechanical and fracture behaviour of hydroxyl functionalized BNNS, three different configurations were designed; fully functionalized, –hydroxyl group was attached to both B and N atoms, whereas in partial, it was attached either to B or N atoms. It was concluded from the simulations that edge and crack edge atom passivation with hydroxyl group have positive effect on the mechanical and fracture behaviour of BNNS, whereas the covering of nanosheet with functional group proved to have detrimental effects on the properties of BNNS. Results presented in this research article will help in exploring the full potential of hydroxyl functionalized BNNS in various applications such as nanocomposite, drug delivery, etc. [ABSTRACT FROM AUTHOR]

The compatibility of polylactic acid (PLA)/polybutylene succinate (PBS) blends was studied by molecular dynamics and mesoscopic dynamics, which is a controversial issue in experiments. Six simulation models of PLA/PBS with different composition ratios (100/0, 90/10, 80/20, 70/30, 60/40, 0/100) were constructed. The radial distribution function, hydrogen bond, free energy density, order parameter and iso-density surface morphology of the PLA/PBS systems were simulated and analyzed. Due to the formation of hydrogen bonds and van der Waals bonds between different elements of PLA chains and PBS chains, the PLA/PBS blends exhibit good compatibility at all composition ratios. [ABSTRACT FROM AUTHOR]

In this investigation, composite materials made from high-density polyethylene (HDPE) and alumina, as well as from HDPE, alumina, and glass fibers, were prepared, aiming to improve the thermal stability, stiffness, and mechanical strength. The combined effects of alumina and glass fibers and the individual effects of alumina were studied. Alumina concentrations ranged from 5 wt% to 10 wt% and glass fiber concentrations ranged from 10 wt% to 30 wt%. For the hybrid composite materials, alumina concentration was maintained constant as the glass fiber concentration increased. The composites were processed with a double-screw extruder. Their properties were evaluated through a multi-analytical approach. Results pointed to a significant increase of the elastic modulus for the hybrid composite (up to 501% in comparison to the neat polymer), at the cost of a large decrease in toughness, alongside a decline in impact resistance. Elastic modulus improvement was observed in both hybrid and HDPE-alumina composites, being higher for the hybrid composites due to the addition of glass fibers. HDPE-alumina composites presented a decrease in mechanical strength, whereas the hybrid composites showed an increase of this parameter. Concerning thermal properties, the hybrid composites presented higher thermal stability than that of the HDPE-alumina composites and a similar degradation temperature as the neat polymer. Micrographs pointed to weak adhesion between alumina particles and the polymeric matrix as well as a slight degree of fiber detachment. Overall, the hybrid composites presented considerably higher stiffness and mechanical strength than the neat polymer and HDPE-alumina composite (19–26% increase), with no significant change in thermal stability. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the effect of molybdenum disulfide on tribological properties of Ultra‐high‐molecular‐weight polyethylene (UHMWPE). UHMWPE/MoS2 nano‐composites were prepared using in‐situ polymerization and Ziegler‐Natta catalytic system. Studies showed that, in order to obtain the optimum tribological properties, interlayer distance between nanosheets should be as high as possible. Therefore, the nanosheets were subjected to oxidation using the required oxidants followed by thermal shock and ultrasound. Fourier‐transform infrared spectroscopy (FTIR) analysis was used to determine the formation of functional groups which indicate the formation of S═O bond in the molybdenum disulfide oxide. Then, in order to exfoliate and increase the interlayer distance of nanosheets, thermal shock and ultrasonic were conducted Field Emission Scanning Electron Microscopy (FESEM) analyses. Finally, the obtained sample was used as the second support of catalyst in in‐situ polymerization process. Then, under specified and constant operational conditions, the synthesis of samples containing 0.5%, 1%, and 2% nanoparticles were conducted. The results of the morphological study with FESEM indicate that the filler is uniformly distributed in the matrix, and X‐ray Powder Diffraction (XRD) analysis showed that completely exfoliated nanocomposites were resulted and in low nanoparticle content. Addition of MoS2 as reinforcing agent had a significant effect on friction coefficient of the nanocomposites. With the addition of 0.5 wt% of MoS2, the friction coefficient declined by approximately 35%. Furthermore, negligible decrease in sample's weight after the wear test is an indication of a strong interaction between MoS2 and the matrix. Scratch resistance test revealed that with the addition of filler, the resistance increased from 23 to 60 MPa. [ABSTRACT FROM AUTHOR]

In recent years, the application of polymer nanocomposites has been enormously increased, particularly in aerospace and automotive sector due to its lightweight and high specific strength. In this study, nanocomposite materials with polypropylene (PP) matrix and Cloisite 30B (C30B) as reinforcing nanofiller with Elvaloy AC 3427 (EA) as compatibilizer were manufactured by melt intercalation technique with the aid of twin-screw extruder (TSE). The C30B with EA was reinforced in the PP matrix at 1, 2, 3 and 5 wt%. The PP/C30B/EA nanocomposites were processed in TSE with different barrel zones such as conveying zone, melting zone, mixing zone and plasticizing zone which helps in achieving homogenous dispersion of C30B in PP matrix. The processing parameters of TSE are twin-screw speed (65 r/min), volumetric feeder’s screw speed (7 r/min), degassing zone pressure (40 mmHg), cooling length (50 cm) and humped temperature profile (170–220°C). The processed PP/C30B/EA was characterized using X-ray diffraction (XRD) for studying intercalation/exfoliation structure formation and transmission electron microscope (TEM) for studying the dispersion of C30B in PP matrix. The thermal characterization of PP/C30B/EA nanocomposites was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The addition of C30B at 5 wt% to PP/C30B/EA nanocomposites increased the DSC, TGA and DMA properties. [ABSTRACT FROM AUTHOR]

The effects of length and content of chain branching on the mechanical properties of polyethylene (PE) in atomic scale were examined by molecular dynamics (MD) simulations. Methyl-, ethyl- and butylgroups were adopted as branched chains to distribute along PE backbones. Plastic flow deformation was captured by providing a uniaxial tensile loading at a given strain rate, which shows the characteristic of rate dependence. Current results are in reasonable agreements with existing experimental data. The statistical results show that the longer length of chain branching induces lower equilibrium density and higher yield strength of branched PE. In addition, higher content of chain branching brings higher equilibrium density and lower yield strength of branched PE. It is assumed that the distribution of dihedral angles influences the deformation of PE definitely. The non-bond interactions contribute to the load-bearing capacity of PE largely. Branched PE shows big differences on mechanical behaviours comparing with the linear one. Chain branching distribution also greatly affects the performance of PE, which needs a further discussion. [ABSTRACT FROM AUTHOR]

Due to their exceptional properties, graphene and hexagonal boron nitride (h‐BN) nanofillers are emerging as potential candidates for reinforcing the polymer‐based nanocomposites. Graphene and h‐BN have comparable mechanical and thermal properties, whereas due to high band gap in h‐BN (~5 eV), have contrasting electrical conductivities. Atomistic modeling techniques are viable alternatives to the costly and time‐consuming experimental techniques, and are accurate enough to predict the mechanical properties, fracture toughness, and thermal conductivities of graphene and h‐BN‐based nanocomposites. Success of any atomistic model entirely depends on the type of interatomic potential used in simulations. This review article encompasses different types of interatomic potentials that can be used for the modeling of graphene, h‐BN, and corresponding nanocomposites, and further elaborates on developments and challenges associated with the classical mechanics‐based approach along with synergic effects of these nano reinforcements on host polymer matrix. This article is categorized under: Molecular and Statistical Mechanics > Molecular Mechanics Structure and Mechanism > Computational Materials Science Molecular and Statistical Mechanics > Molecular Dynamics and Monte‐Carlo Methods [ABSTRACT FROM AUTHOR]

Halloysite nanotubes (HNTs) and intumescent flame retardant (IFR)-filled 80/20 (wt/wt) polypropylene/acrylonitrile–butadiene–styrene (PP/ABS) blend and their composites in the presence of dual compatibilizer have been prepared using twin screw extruder followed by injection molding. There exists the formation of α- and β-form of PP crystals in addition to enhancement in crystallinity of PP phase by an addition of HNTs and IFR in 80/20 (wt/wt) PP/ABS blend and their composites in the presence of dual compatibilizer. In addition, scanning electron microscopy (SEM) reveals the formation of matrix-droplet morphology, and the dispersion of HNTs and IFR in 80/20 (wt/wt) PP/ABS blend and its composites in the presence of dual compatibilizer results in a refinement in matrix-droplet morphology. This has resulted in an enhancement in tensile and impact properties of HNTs- and IFR-filled 80/20 (wt/wt) PP/ABS blend and their composites in the presence of dual compatibilizer. Thermal stability also increases by an addition of HNTs and IFR in 80/20 (wt/wt) PP/ABS blend and their composites in the presence of dual compatibilizer due to formation of intumescent char. [ABSTRACT FROM AUTHOR]

Interaction between nanoparticles (NPs) and pulmonary surfactant monolayer plays a very significant role in nanoparticle-based pulmonary drug delivery system. Previous researches have indicated that different properties of nanoparticles can affect their translocation across pulmonary surfactant monolayer. Here we performed coarse-grained molecular dynamics simulation aimed at nanoparticles’ surface charge density effect on their penetration behaviours. Several hydrophilic nanoparticles with different surface charge densities were modelled in the simulations. The results show that NPs’ surface charge density affects their translocation capability: the higher the surface charge densities of NPs are, the worse their translocation capability is. It will cause the structural changes of pulmonary surfactant monolayer, and inhibit the normal phase transition of the monolayer during the compression process. Besides, charged NPs can be adsorbed on the surface of the monolayer after translocation as a stable state, and the adsorption capability of NPs increases generally with the increase of surface charge densities. Our simulation results suggest that the study of nanoparticle-based pulmonary drug delivery system should consider the nanoparticles’ surface charge density effect in order to avoid biological toxicity and improve efficacy. [ABSTRACT FROM PUBLISHER]

This paper investigates the performance of polypropylene (PP) incorporated with montmorillonite (MMT) nanoclay, maleic anhydride grafted PP (PP-g-MAH), and pro-degradant additive (TDPA®), which provides additional benefits of increasing biodegradability. A twin-screw extruder was used to compound PP, MMT, PP-g-MAH, and TDPA, and the extruded nanocomposite films were collected for testing, and their mechanical, thermal, barrier, oxo-biodegradability, and morphological properties were evaluated. Tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), oxygen permeability test, soil burial test, X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscope (SEM) analysis were used to investigate these properties. Increasing MMT content from 1 to 3 phr increases tensile strength and Young’s modulus of the neat PP samples up to ca.45% and 27% respectively. Improvement of thermal properties for neat PP samples was observed by increasing MMT content from 1 to 3 phr. However, at 4 phr MMT content, both mechanical and thermal properties of nanocomposites dropped slightly. For soil buried samples, DSC and TGA results revealed significant changes in the thermal properties for PP samples containing TDPE additive compared to neat PP, clearly confirming the effectiveness of this TDPA additive in promoting oxo-biodegradation process of PP. Similarly weight loss evaluation result shows that about 4% weight loss for sample (PP/TD), which is PP and TDPA blend only, compared to neat PP. However, increasing MMT content from 1 to 4 phr slightly reduced weight loss of PP from 3.5 to 1.5%, respectively, for 6 month soil exposure period, which indicates that increasing MMT content was detrimental to the degradation process. For higher MMT content, the oxygen permeability of PP nanocomposites was decreased by 46% of the corresponding values for neat PP. The XRD and TEM results confirmed the exfoliation structure of the nanocomposites. The morphological change after soil burial test was studied using scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

In this paper, we investigate the fast flow in nanochannels, which is induced by the travelling surface waves. The nanoscale fluid mechanism in nanochannels has been influenced by both amplitude and frequency of travelling surface waves, and the hydrodynamic characteristics have been obtained by molecular dynamics simulations. It has been found that the flow rate is an increasing function of the amplitude of travelling surface waves and can be up to a sevenfold increase. However, the flow rate is only enhanced in the limited range of frequency of travelling surface waves such as low frequencies, and a maximum fivefold increase in flow rate is pronounced. In addition, the fluid-wall interaction (surface wettability) plays an important role in the nanoscale transport phenomena, and the flow rate is significantly increased under a strong fluid-wall interaction (hydrophilicity) in the presence of travelling surface waves. Moreover, the friction coefficient on the wall of nanochannels is decreased obviously due to the large slip length, and the shear viscosity of fluid on the hydrophobic surface is increased by travelling surface waves. It can be concluded that the travelling surface wave has a potential function to facilitate the flow in nanochannels with respect to the decrease in surface friction on the walls. Our results allow to define better strategies for the fast nanofluidics by travelling surface waves. [ABSTRACT FROM AUTHOR]

In this article, the polypropylene (PP) nanocomposites containing nanoclay particles and basalt fiber (BF) are prepared in the presence of maleic anhydride grafted PP (PP-g-MA) as compatibilizing agent. The Charpy impact behavior of PP/PP-g-MA/clay nanocomposites and PP/PP-g-MA/Clay/BF nanocomposites at room temperature (25°C), cryogenic temperature (–196°C), and high temperature (120°C) is presented. The BFs prevented the PP matrix from plastic deformation, but the impact strength improvement of nanocomposites is obtained when nanoclay in the PP matrix resists the propagation of cracks. The fracture surfaces are examined with scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

The engineering applications of thermoplastics have been increased in the last few years by blending the thermoplastic polymer with fillers, which is a common methodology to develop thermoplastic polymer with boosted properties. In this investigation, the polypropylene thermoplastic polymer and Cloisite 30B (1, 2, 3, and 5 wt. %) as a nano filler with Elvaloy AC 3427 were mixed using Twin screw. The Elvaloy AC 3427 was used as a compatibilizer to enhance the dispersion of Cloisite 30B in polypropylene matrix. The polypropylene/Cloisite 30B/Elvaloy AC 3427 nanocomposite was investigated with X-ray diffraction shows an increase in d-spacing with an intercalated structure. Polypropylene/Cloisite 30B/Elvaloy AC 3427 nanocomposite was mechanically and metallurgically characterized. To validate the tensile properties of polypropylene/Cloisite 30B/Elvaloy AC 3427 nanocomposites, different mathematical modeling was used. The result shows an improvement in properties due to the fine dispersion of Cloisite 30B in polypropylene matrix in the presence of Elvaloy AC 3427 compatibilizer, and the same was justified with Field Emission Scanning Electron Microscopy. [ABSTRACT FROM AUTHOR]

The objective of this work was to find a possible engineering application for polypropylene (PP) by preparing fibers filled with nanoclay particles. Unfilled and nanoclay filled (0-5 wt%) PP fibers were continuously drawn and examined. The surface morphology and topographic studies of fibers were carried out using a scanning electron microscope (SEM). It was observed that unfilled PP fibers possess poor density distribution with the nonuniform diameter across the fiber length affecting structural integrity. However, PP fibers filled with = 2 wt% nanoclay had shown improvement in structural integrity. The structure and morphology of fibers were examined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis, and the result indicated good dispersion of nanolayers of clay in PP matrix with exfoliated nanocomposite structure up to 2 wt% nanoclay and above 2 wt% showing intercalated nanocomposite structure. Improved tensile, thermal and water barrier properties of nanoclay filled PP were also observed. [ABSTRACT FROM AUTHOR]

In this study, polypropylene/carbon nanotube nanocomposites were prepared via in situ polymerization using a bi-supported Ziegler − Natta catalytic system. In this system, magnesium ethoxide and multiwall carbon nanotubes ( MWCNTs) are jointly used as catalyst supports. SEM images reveal the distribution and quite good dispersion of MWCNTs throughout the polypropylene ( PP) matrix. The thermal properties of the samples were examined using DSC and TGA tests. The results show that the crystallization temperature of the nanocomposites significantly increases while the melting point is not markedly affected. In addition, the thermal stability is improved. The melt rheological properties of PP/ MWCNT nanocomposites in the linear and nonlinear viscoelastic response regions were studied. An increment of the complex viscosity ( η*), storage modulus ( G′) and loss modulus ( G′′) and a decrement of the loss factor (tan δ) compared with neat PP are observed. Steady shear flow experiments show an increase in shear viscosity with increasing the MWCNT content. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A mesoporous-type catalytic support was synthesized through the modification of a smectite with polyvinyl alcohol (PVA) and microwaves. Texture and micro-morphology of the support was determined. Several techniques were employed in order to describe the chemical environment of active species on the surface. Ni particle sizes were dependent on the structural site of reducible species. High stable Ni-Ce catalysts (calcined at 800 °C) were evaluated in the CO reforming of methane reaction at 700 °C (WHSV = 96 L g h, without dilution gas and pre-reduction). The catalysts have presented CH conversions between 40 and 65%, CO conversion between 35 and 65% and H/CO ratios between 0.2 and 0.4. Graphical Abstract: Delaminated-clay was synthesized from a natural smectite using polyvinyl alcohol and microwaves. Ni-Ce catalysts supported on delaminated clay achieved high stability in dry reforming of methane for syngas production. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this study, molecular dynamics simulations have been used to investigate the behavior of the drug rivastigmine and its carrier so-called poly (n-butyl cyanoacrylate) in the encapsulation process. Polymer modeling, and subsequently the emulsion polymerization model, were applied to analyze drug release in vitro and to justify rivastigmine transport across the blood-brain barrier (BBB) and polymer agglomeration. On the other hand, suitable polymer chain length, encapsulation method, polarity between polymer and drug structure, and finally, pattern of drug released in vitro and in vivo have been investigated to analyze the behavior of drug and polymer accurately. Maximum drug loading was determined based on the modeling of drug encapsulation and comparison of the radius of gyration of polymer (Rg) and distance between center of masses (COMs) of rivastigmine molecules and polymer in equilibrium condition (A°). With the aim of better understanding of drug release, we calculated the Flory-Huggins interaction parameter, diffusion coefficient, and intermolecular interaction energy. The results reveal that more drug molecules remain on the surface of the polymeric structure, with increasing the concentration of rivastigmine molecules from 3 up to 7, but the number of encapsulated drug molecules inside of the polymer remains constant. Also, calculated values of Gibbs free energy indicated that intramolecular interactions of the polymer chain overcome the intermolecular interactions between polymer and drug. Therefore, any extra loading of drug resulted in accumulation on the polymer surface.Poly (n-butyl cyanoacrylate) containing rivastigmine molecules [ABSTRACT FROM AUTHOR]