Composition Weight Ratio Research Articles

Self-assembled phases of block copolymer blend thin films.

The patterns formed by self-assembled thin films of blended cylindrical and lamellar polystyrene-b-poly(methyl methacrylate) block copolymers can be either a spatially uniform, single type of nanostructure or separate, coexisting regions of cylinders and lamellae, depending on fractional composition and molecular weight ratio of the blend constituents. In blends of block copolymers with different molecular weights, the morphology of the smaller molecular weight component more strongly dictates the resulting pattern. Although molecular scale chain mixing distorts microdomain characteristic length scales from those of the pure components, even coexisting morphologies exhibit the same domain spacing. We quantitatively account for the phase behavior of thin-film blends of cylinders and lamellae using a physical, thermodynamic model balancing the energy of chain distortions with the entropy of mixing.

Effective nanoconfinement of 2LiBH4–MgH2 via simply MgH2 premilling for reversible hydrogen storages

To improve nanoconfinement of LiBH4 and MgH2 in carbon aerogel scaffold (CAS), particle size reduction of MgH2 by premilling technique before melt infiltration is proposed. MgH2 is premilled for 5 h prior to milling with LiBH4 and nanoconfinement in CAS to obtained nanoconfined 2LiBH4–premilled MgH2. Significant confinement of both LiBH4 and MgH2 in CAS, confirmed by SEM–EDS–mapping results, is achieved due to MgH2 premilling. Due to effective nanoconfinement, enhancement of CAS:hydride composite weight ratio to 1:1, resulting in increase of hydrogen storage capacity, is possible. Nanoconfined 2LiBH4–premilled MgH2 reveals a single–step dehydrogenation at 345 °C with no B2H6 release, while dehydrogenation of nanoconfined sample without MgH2 premilling performs in multiple steps at elevated temperatures (up to 430 °C) together with considerable amount of B2H6 release. Activation energy (EA) for the main dehydrogenation of nanoconfined 2LiBH4–premilled MgH2 is considerably lower than those of LiBH4 and MgH2 of bulk 2LiBH4–MgH2 (ΔEA = 31.9 and 55.8 kJ/mol with respect to LiBH4 and MgH2, respectively). Approximately twice faster dehydrogenation rate are accomplished after MgH2 premilling. Three hydrogen release (T = 320 °C, P(H2) = 3–4 bar) and uptake (T = 320–325 °C, P(H2) = 84 bar) cycles of nanoconfined 2LiBH4–premilled MgH2 reveal up to 4.96 wt. % H2 (10 wt. % H2 with respect to hydride composite content), while the 1st desorption of nanoconfined sample without MgH2 premilling gives 4.30 wt. % of combined B2H6 and H2 gases. It should be remarked that not only kinetic improvement and B2H6 suppression are obtained by MgH2 premilling, but also the lowest dehydrogenation temperature (T = 320 °C) among other modified 2LiBH4–MgH2 systems is acquired.

Toughening epoxy resins by modification with in situ polymerized acrylate copolymer composed of butyl acrylate and glycidyl methacrylate

Poly(butyl acrylate–glycidyl methacrylate) (PBG) was prepared by in situ polymerization of butyl acrylate (BA) and glycidyl methacrylate (GMA) and further used as a modifier to improve the comprehensive properties of the epoxy resin curing system. The modified resin system was based on diglycidyl ether of bisphenol, methyl tetrahydrophthalic anhydride, and tris(dimethylaminomethyl)phenol. The influence of copolymer composition on the mechanical properties, thermal performance, and phase behavior of the system was carefully examined. Results showed that the addition of PBG greatly improved the impact strength of the modified epoxy resin. When 15 wt% of the BA/GMA with a weight ratio composition of 7.5/7.5 was added to the epoxy, high-performance-modified epoxy resin was obtained.

Toughening of Epoxy Resin Modified with <i>In Situ</i> Polymerized Acrylate Copolymer

P(BA-St), a good modifier for epoxy resin, was prepared by BA and St in situ polymerization. The modified resin system was based on diglycidyl ether of bisphenol and methyl tetrahydrophthalic anhydride, tris (dimethylaminomethyl) phenol. The influence of the copolymer on mechanical properties and thermal performance of the systems was studied. When 15 wt% of the BA/St with a weight ratio composition of 7.5/7.5 was added to epoxy, high performance modified epoxy resin was obtained.

치과용 의치상 아크릴릭 레진 단량체 중량비에 따른 기계적 성질

Purpose: This study is to provide basic data of the dental acrylic denture base resin in the mechanical property difference investigation according to the monomer composition weight ratio of the acrylic denture base resin. Methods: The monomer composition of the acrylic denture base resin and weight ratio makes the different specimen. It measured the mechanical property with the specimens through Hardness Test, Tensile Test, Flexural Test, Flexural Modulus, FT-IR Test. Results: The control group Vertex was 18.4 Hv and the experimental group MED was 14.46~19.07Hv in the hardness test. Vertex was 364N, MED-3 was lowest in the tensile strength test and the Head of a family cursor declination was big. The result declination of the experimental specimens showed. Vertex and MED-2 was the highestest in the flexural test and after coming MED-6, MED-5, MED-1, MED-3, MED-4. Vertex and MED-2, as to a spectrum for 500~1800 -1 peak can show the excellent degree of polymerization in the FT-IR Test. Conclusion: The ideal weight ratio of the monomer of the acrylic denture base resin of which the mechanical property is the highestest was MMA 100g, EDGMA 5g, DMA 0.2g, of MED-2.

Toward binder-free electrochemical capacitor electrodes of vanadium oxide-nanostructured carbon by supercritical fluid deposition: Precursor adsorption and conversion, and electrode performance

Electrochemical capacitor electrodes were fabricated by depositing an ultra-thin layer of vanadium oxide on a high conducting, large specific surface area (SSA) materials (substrates) using a supercritical fluid adsorption–calcination method. The high SSA materials included binder free single walled carbon nanotube–activated carbon (SWCNT–AC) composites and the traditional electrode of activated carbon–carbon black–polymer binder (AC–CB–binder). The uptake of the organometallic precursor for the oxide (vanadium (III) acetylacetonate) on the substrates were investigated and related to their SSA. Precursor uptakes up to 54.7 wt% of the initial carbon substrate was achieved. Calcination conditions for converting the precursor to oxide and electrochemical properties of the electrodes were thoroughly investigated. The V2O5, which showed extremely high specific pseudo-capacitance (>1000 F g−1 at 100 mV s−1), greatly enhanced the overall electrode performances. Conversely, the V2O5 pseudo-capacitance was better utilized in the SWCNT–AC substrate, particularly at high working speeds, because of the significantly higher electrical conductivity. For example, the SWCNT–AC–V2O5 composite (weight ratio 40:60) had its volumetric capacitance doubled, comparing to the ∼50% increase in the AC–CB–binder sample at 100 mV s−1.

Mechanism of Nanoparticle Formation from Ternary Coground Phenytoin and Its Derivatives

The mechanism of drug nanoparticle formation of phenytoin (DPH) and its derivatives monomethylphenytoin (MDPH) and dimethylphenytoin (DMDPH) was investigated. The drug, polyvinylpyrrolidone K17 (PVP), and sodium dodecyl sulfate were coground to obtain the ground mixture (GM). The DPH GM was amorphous; however, MDPH and DMDPH GMs contained drug crystals. Spectral changes in infrared and (13)C solid-state nuclear magnetic resonance were observed in the DPH GM, partially observed in the MDPH GM, and hardly observed in the DMDPH GM. Mean particle sizes of the DPH, MDPH, and DMDPH GM nanosuspension were almost the same; however, stability after storage differed in the order of DPH > MDPH > DMDPH. The intermolecular interaction between the drug and PVP reflected not only the crystallinity of the drug in the GM but also the stability of the GM suspension. The size and stiffness of drug nanoparticles were evaluated using atomic force microscopy. Crystallization of the amorphous GM and agglomeration of the primary nanocrystals were observed in the DPH GM suspension. In contrast, primary nanocrystals were observed in the DMDPH GM suspension. The size of the drug nanocrystals formed from the different molecular states of the drug in the GM reflects the agglomerated states in water and stability.

Rat bone marrow stromal cells-seeded porous gelatin/tricalcium phosphate/oligomeric proanthocyanidins composite scaffold for bone repair

Repair of bone defects remains a major challenge in orthopaedic surgery. Bone tissue engineering is an attractive approach for treating bone loss in various shapes and amounts. The aim of this study was to prepare and evaluate the feasibility of a porous scaffold, which was composed of oligomeric proanthocyanidin crosslinked gelatin mixed with β-tricalcium phosphate (GTP) and was seeded with bone marrow stromal cells (BMSCs) as a bone substitute. GTP scaffolds were made porous using a salt-leaching method. The physicochemical properties of the scaffold were evaluated to determine the optimal salt:composite weight ratio. The results indicated that the GTP scaffold had a favourable macroporous structure and higher porosity when the salt:composite weight ratio was 4:1. Cytotoxic tests demonstrated that extracts from the GTP scaffolds promoted the proliferation of BMSCs. Rat BMSCs were seeded on a GTP scaffold and cultured in a spinner flask. After 2 weeks of culture, scanning electron microscopy observation showed that the cells adhered well to the surfaces of the pores in the scaffold. Moreover, this study explored the biological response of rat calvarial bone to the scaffold to evaluate its potential in bone tissue engineering. Bone defects were filled with BMSC-seeded GTP scaffold and acellular GTP scaffold. After 8 weeks, the scaffold induced new bone formation at a bone defect, as was confirmed by X-ray microradiography and histology. The BMSC-seeded scaffold induced more new bone formation than did an acellular scaffold. These observations suggest that the BMSCs-seeded GTP scaffold can promote the regeneration of defective bone tissue.

STRENGTH PREDICTION OF DIFFERENT ORIENTATION UNIDIRECTIONAL GLASS FIBER LAP JOINTS

Composite materials have made way to various fields, including aerospace structures, underwater vehicles, automobiles and robot systems. Due to the high strength to weight ratio of composites, they serve as a suitable alternative to metals, therefore making the need for a reliable database of structural design more important. Most of the modern civilian and military aircraft use composite materials for their primary structural components (in addition to metals). One of the key areas in composite structural design involves the tensile strength of joints. In the present work, the lap joints fabricated from different orientations of GFRP (Glass fiber reinforced polymer) specimens are subjected to tensile test. The effect of fibre orientation on the tensile strength of lap joint is investigated both experimentally and computationally using conventional software package. The experimental results are compared with FEA using conventional software package ANSYS.

Investigation of Relations between Atomic Number and Composition Weight Ratio in PZT and SMA and Prediction of Mechanical Behavior

In this paper there is presented the mechanical behavior of the one lead–zirconate–titanate by its atomicnumberanditscertainmechanicalbehaviorissimulatedbythemathematicalmodelingandABAQUSsoftwareforsmartmaterials,aswellaspredictionofmechanicalbehaviors. Alsointhissmartmaterial(Pb–Zr–Ti)thegrainsizeaccordingtomolarratioisstudied. Thismechanicalbehaviorismodeledbytheexponentialandpolynomialformulafromonetotendegree. Nexttherearedefinedthenewrelationsformechanicalbehaviorandcompositionweight ratio, between composed elements for triplex lead–zirconate–titanate and dual smart materials. Triplexlead–zirconate–titanatehasbeenselectedasmainandimportantmaterialforthedevelopmentofsmartstructures.In addition, the relation between atomic number and weight ratio in one smart material (Ni–Ti) is investigatedbriefly. Inthiswork,changeofresistanceandvoltage,pressure,grainsize,molarratio,residualstress,contentofzirconateandtheothermechanicalpropertiesarestudied.PACS:31.15.–p,31.10.+z,32.10.–f

Fabrication of Composite Materials Using Coal Ash and Aluminum Sludge by Spark Plasma Sintering

Coal ash and aluminum sludge are industrial wastes discharged in large amounts by electric power plants and aluminum sash factories. In this study, aluminum sludge was heat treated at a temperature of 1573K for 2 hours to change the α-alumina crystal structure. The silica (SiO2) contained in coal ash and the alumina (Al2O3) contained in aluminum sludge were combined to synthesize mullite by using a spark plasma sintering apparatus. While varying the composition ratio of the fly ash and α-alumina sludge, the mechanical properties were investigated. As a result, the bending strength of the composite material (composition weight ratio of coal ash and α-alumina sludge 2:3) showed an extremely high value of 270MPa at a sintering temperature of 1573K and holding pressure of 40MPa. Using X-ray analysis, the existence of mullite crystal structures in this material was confirmed.

Electrospinning and Mechanical Properties of Polystyrene and Styrene-Isoprene-Styrene Block Copolymer Blend Nanofibres

Electrospinning of polystyrene (PS) and styrene–isoprene–styrene block copolymer (SIS) blends with different composition weight ratios was carried out with a mixed solvent, tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) (80/20, v/v). Electrospun PS/SIS blend fibers were characterized using scanning electron microscopy. The results indicated that the presence of DMF resulted in a beneficial effect on fiber formation and greater electrospinnability of as-spun fibers. Furthermore, the morphological structure and diameters of as-spun fibers from PS and SIS blends were affected by the composition weight ratio and the solution properties. The fibers from 10 wt% solution exhibited the best mechanical properties compared to the fibers from other concentrations for the same composition, and increasing the SIS content one observes a vanishing of PS-related properties, while SIS-related properties emerges.

Studies on the electrospun submicron fibers of SIS and its mechanical properties

AbstractThe submicron fibers were prepared via electrospinning the styrene–isoprene–styrene (SIS) triblock copolymer from a pure solvent of tetrahydrofuran (THF) and a mixed solvent of THF and N, N‐dimethylformamide (DMF). The addition of DMF to THF resulted in a beneficial effect on the fiber formation and the electrospinnability. The obtained results revealed that the fibers were only formed in a narrow solution concentration range of 8–15 wt %; the morphology, diameter, structure, and mechanical performance of as‐spun fibers from PS and SIS solutions were affected by the composition weight ratio and the solution properties; and those from the solution at the intermediate concentration of 10 wt % exhibited a maximum tensile strength and strain at break. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The performance of solar cell based on the blend of MEH-PPV∶TiO2

The solar cells based on the blend of MEH-PPV(poly(2-methoxy-5-(2′-ethylhexoxy)- 1,4-phenylene vinylene) as donor and TiO2 nanorods as acceptor were fabricated. We analyzed the cause of performance change of the device in detail by the ultraviolet-visible absorption spectroscopy(UV-vis), photoluminescence spectroscopy(PL), the current density-voltage(J-V) curve. When TiO2 nanorods are dispersed in a polymer matrix, the performance of the device is greatly enhanced. The highest efficiency is achieved for the 1∶3 (MEH-PPV: TiO2 nanorods) weight ratio composition. We get an open circuit voltage of 0.7V, short circuit current density of 0.41 mA/cm2 and fill factor of 31.8% under air-mass 1.5 solar simulator illumination, yielding a 0.091% power conversion efficiency (PCE)，which is a nearly 60 times enhancement over the PCE of the device based on the MEH-PPV as active layer. The device PCE is further increased twofold by refluxing in phenthiol.

Optically Transparent, Amphiphilic Networks Based on Blends of Perfluoropolyethers and Poly(ethylene glycol)

Amphiphilic networks of perfluoropolyethers (PFPE) and poly(ethylene glycol) (PEG) have been achieved to yield optically transparent, mechanically robust films over a wide range of compositions. Telechelic diols of these oligomers were transformed to a photocurable dimethacryloxy form (DMA) and free radically cured at various composition weight ratios to yield free-standing films. Clear and colorless amphiphilic networks could be achieved when low molar mass versions of both the PFPE-DMA (1 kg/mol) and the PEG-DMA (550 g/mol) were used. The bulk morphologies of the samples were extensively characterized by a variety of techniques including ultraviolet-visible spectroscopy, differential scanning calorimetry, dynamic mechanic thermal analysis, small-angle X-ray scattering, atomic force microscopy, X-ray photoelectron spectroscopy, and optical microscopy, which strongly suggest that nanoscopic to macroscopic phase-separated materials could be achieved. By incorporating a threshold amount of PFPEs into PEG-based hydrogel networks, water swelling could be significantly reduced, which may offer a new strategy for a number of medical device applications. Along these lines, strong inhibition of nonspecific protein adsorption could be achieved with these amphiphilic network materials compared with an oligo(ethylene glycol)-based self-assembled monolayer coated surface.

Morphological and Scattering Studies of Binary Mixtures of Block Copolymers: Cosurfactant Effects Observed in the Parameter Space of Temperature, Blend Composition, and Molecular Weight Ratio

Thermoreversible order-order transitions or “order−distorted order” transitions (defined “OOT” for simplicity) between various morphologies occurring on binary mixtures of diblock copolymers were investigated by using small-angle X-ray scattering. The mixtures were composed of a long asymmetric polystyrene-block-polyisoprene (SI) having a spherical morphology and a short symmetric SI, which are hereafter denoted as as and s3, respectively. The symmetric diblock, s3, is short enough to be in a disordered state at room temperature. Upon raising temperature from ambient temperature toward order−disorder or “distorted order-disorder” transition temperature, a unique re-entrant bicontinuous-cylinder- bicontinuous OOT was observed for as/s3 = 85/15 and 82/18 (w/w). Other types of OOT, such as cylinder-sphere and lamella-bicontinuous, were observed on the as/s3 mixtures of different compositions. These OOTs were characterized by monitoring the evolution of the inverse peak scattered intensity, the square of the half-width at half-maximum of the peak, and the characteristic period of the microdomains, as a function of temperature, T. The complex morphological behaviors observed here can be understood on the basis of two key features of the binary blends: the cosurfactant effect and the possibility for the chemical junctions of the shorter diblock to migrate away from the interface as segregation power decreases. As a summary of this series of studies, a three-dimensional phase diagram was constructed in the parameter space of overall volume fraction of PS block in the mixture, the ratio of the degree of polymerization of as to that of s3 and T. Such a phase diagram illustrates that the cosurfactant effect opens perspectives in tailoring morphologies of self-assembled, nanostructured materials.

Composition and annealing effects in polythiophene/fullerene solar cells

We have fabricated organic solar cells with blends of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) as electron donor and electron acceptor, respectively. Blend composition and device annealing effects were investigated with optical absorption and photoluminescence spectroscopy, atomic force microscopy, photocurrent spectroscopy, and current-voltage characteristic measurements on devices under monochromatic or air mass (AM) 1.5 simulated solar light illumination. The highest efficiency was achieved for the 1:1 (P3HT:PCBM) weight ratio composition. The good performance is attributed to an optimized morphology that enables close intermolecular packing of P3HT chains. Inferior performance for the 1:2 composition is attributed to poorer intermolecular packing with increased PCBM content, while phase segregation on a sub-micron scale was observed for the 1:4 composition. The power conversion efficiency (AM 1.5) was doubled by the thermal annealing of devices at 140∘C to reach a value of 1.4%.

Influence of nanomorphology on the photovoltaic action of polymer–fullerenecomposites

Composites of conjugated poly(3-hexylthiophene) (P3HT) and the fullerene derivative[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) demonstrate an efficient photogeneration of mobilecharge carriers. Thermal annealing of P3HT:PCBM based devices gives rise to asignificant increase of the photovoltaic efficiency, as follows from measurements ofthe external quantum efficiency and the current–voltage characteristics. Uponannealing, the absorption spectrum of the P3HT:PCBM composite undergoes a strongmodification, whereas in the pure components it remains unchanged. The absorption ofthe annealed blends becomes stronger and red shifted in the wavelength regionascribed to P3HT, while the absorption due to the PCBM contribution does notchange. Atomic force microscope measurements on P3HT:PCBM disclose somevariation in morphology due to the crystallization of PCBM. The concentration ofthe PCBM clusters and their size (up to 500 nm) were found to be correlatedwith the amount of PCBM in the blend. We have studied the performance ofphotovoltaic devices with different weight ratios of P3HT:PCBM, namely, 1:3, 1:2,1:1.5, 1:1, 1:0.9, 1:0.8, and 1:0.7. The photocurrent and the power conversionefficiency showed a maximum between 1:1 and 1:0.9. We conclude the variation in theabsorption spectrum and the red shift to result from molecular diffusion of PCBMout of the polymer matrix upon annealing. The growth of the PCBM clustersleads to formation of percolation paths and, therefore, improves the photocurrent.Above a certain concentration, the PCBM crystals provide mechanical stress onthe metal electrode, therefore possibly damaging the interface. Optimization ofthe composite weight ratio reveals the important role played by morphology forthe transport properties of bulk heterojunction P3HT:PCBM based solar cells.

Kinetic Pathways in the Atmospheric Chemistry of Titan – a Generalized Analysis

Titan, the sixth Saturnine moon, is a unique celestial body in many respects, including the existence of a high-density atmosphere over a relatively small astro-physical object, chemical activity in the low-potential reducing medium, the presence of an extensive aerosol domain, etc. Despite many observations, simulation experiments and theoretical models, the general picture of Titan's atmospheric photochemistry is still imprecise. This study of the most general features of chemical activity in Titan's atmosphere by means of Generalized Kinetic Analysis (GKA) is based on the point that both the probability and efficiency of kinetic trends are estimated solely on the basis of energy/material restrictions and general kinetic laws. Only the quantity (intensity) and quality (spectrum) of the external driving force are considered closely, while both the particular kinetic demands and low internal energy resources of Titan's background are discounted. What this means is that the main inferences of GKA should be valid for any given kinetic model. Only a small part Lch of the total external energy flux Labs∼12·6 W m−2 is photochemically active Lch = (L1ion + L2ion + L1dis) + L2ch = (1·5 X 10−3 + 0·22 X 10−3 + 10·6 X 10−3) + 0·69 W m−2. The secondary energy L2ch (1440<λ<3500Å) meets the common energy requirements, while the primary energies L1ion, L2ion and L1dis define kinetic pathways of the chemical process, i.e. L1ion (790<λ<980Å) and L2ion (λ<790Å) initiate ionic photochemistry via ionization of CH4 and N2, respectively, while L1dis (980<λ<1440Å) provides photodissociation of CH4 to neutral species. Because of severe energy/material restrictions, the general chemical process proceeds in the form of a self-sustaining Diels-Alder diene low-temperature synthesis to give telomerization and polymerization. GKA proves that the main kinetic pathways (photodissociation to neutrals and charged photoionization) play different roles with respect to the quantitative and qualitative formation of the final stable products of Titan's atmospheric photochemistry. The neutral pathway governs the bulk (overall yield) of the final products while ionic chemistry is responsible for its wide chemical composition (variety of chemical species). Species identification in terms of hydrocarbon type content results in the following weight ratio composition of the final products: dienes (0·60–0·65) + saturated/unsaturated acyclic pure hydrocarbons (0·16–0·19) + tholins (0·07–0·08) + isocyclics (0·03–0·05) + miscellaneous (0·05). The elemental composition of this bulk material is (C/H/N)∼1·00/ 1·12/ 0·08.

Polypropylene/Silica/Rice Husk Ash Hybrid Composites: A Study on the Mechanical, Water Absorption and Morphological Properties

Polypropylene hybrid composites were made using silica and white rice husk ash (WRHA) fillers as reinforcing agents in the polypropylene (PP) matrix. Both fillers were used at the similar total filler loading i.e., 40% by weight of PP matrix. Results indicate that the increasing loading of WRHA in silica/WRHA weight ratio has increased the flexural modulus and tensile modulus but decrease the tensile strength, stress at yield, elongation at break, Eb and water absorption of PP/silica/WRHA hybrid composites. Degradation study shows that percentage loss of above properties increases with increasing the loading of WRHA in silica/WRHA weight ratio of composites. Scanning electron microscopy (SEM) of tensile fracture surfaces of composites indicates that silica has better adhesion with PP matrix compared to WRHA.