Field,temperature and thickness dependent electron transport in 5,5′-(2,6-di-tert-butylanthracene-9,10-diyl)bis(2-p-tolyl-1,3,4-oxadiazole)

Charge transport in 5,5′-(2,6-di-tert-butylanthracene-9,10-diyl)bis(2-p-tolyl-1,3,4-oxadiazole) is investigated as a function of temperature and organic layer thickness. The thickness dependence of the current indicates towards the trap charge limited conduction (TCLC) with a field and temperature dependent mobility. The density of trap states has been found to be dependent on sample thickness. As the thickness has increased from 80 nm to 120 nm, trap energy has correspondingly increased from 78 meV to 130 meV. TCLC model with Poole Frenkel type field dependent mobility has been fitted into the data and has been found in excellent agreement. Temperature dependency of zero field mobility (μ₀) and β has been estimated from the model.     

Evolution of deformation and friction during multimode scratch test on TiN coated D9 steel

Three different scratch modes were used to induce deformation in TiN coating deposited on D9 substrate. The consequent surface damage was analyzed using optical and scanning electron microscopy. Main deformation mechanisms found during Progressive Load Scratch Test and Constant Load Scratch Test were cohesive cracking, coating spallation and adhesive failure. However, ductile fracture was induced during Multi Pass Scratch Tests (MPSTs) performed at three different loads. The trend of evolving coefficient of friction was found to be different for three kinds of scratch modes and the evolution of coefficient of friction has been correlated with coating deformation.     

ZrO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> Mixed Oxides Xerogel and Aerogel as Solid Acid Catalysts for Solvent Free Isomerization of α-Pinene and Dehydration of 4-Methyl-2-Pentanol

Abstract  

Sulfated and non-sulfated ZrO₂–SiO₂ mixed oxide xerogel and aerogel samples having varied Zr/Si molar ratio were evaluated as solid acid catalysts for the isomerization of α-pinene and dehydration of 4-methyl-2-pentanol. Sulfation resulted into enhancement in the catalytic activity of both xerogel and aerogel samples towards the studied reactions. For example, sulfated catalysts showed 86–98% conversion of α-pinene and 8–35% conversion of 4-methyl-2-pentanol. The selectivity data for camphene and limonene indicated the requirement of moderate acidity. The correlation with cyclohexanol dehydration showed that isomerization of α-pinene is a Br?nsted acid catalyzed reaction. The relationship of 4-methyl-2-pentanol conversion with acid site density and sulfur per unit area was found to be linear.     

Synthesis and characterization of poly(HEMA‐MAA) hydrogel carrier for oral delivery of insulin

Poly(HEMA‐MAA) hydrogel particles were synthesized by redox free‐radical polymerization using 2‐hydroxyethylmethacrylate, different concentration of methacrylic acid as monomer, ethyleneglycol dimethacrylate as crosslinking agent, and APS/TEMED as free‐radical initiator. Fourier transform infrared spectrum of poly(HEMA‐MAA) hydrogels showed intense absorption peak of carbonyl group at ～ 1700 cm^?1 due to carboxylic acid groups of MAA, peak at ～ 2960 cm^?1 due to CH stretching and vinylic peak at 1700 cm^?1 independent of MAA concentration. Highest swelling percentage 587% was observed in case of poly(HEMA‐MAA) hydrogel synthesized using 30% of MAA while lowest swelling percentage 413% was observed in hydrogel synthesized 10% of MAA at basic pH (8.0). Scanning electron micrograph of copolymeric particles showed the irregular shape of poly(HEMA‐MAA) particles with conglomeration with each due to ionization of carboxylic groups. Insulin was radiolabeled using technetium‐99m radionuclide and the radiolabeling efficiency was found to be 99%. Poly(HEMA‐MAA) hydrogel having 60% of MAA showed the highest insulin loading efficiency of 68% while lowest 37% was observed in case of 10% MAA hydrogel. Insulin release studies showed only 35–65% of insulin was released into the medium from particles at pH 2.5 in 60 min, while insulin release was significantly higher at pH 7.4. Hypoglycemic effect of the 60 and 80 I.U./kg insulin dose loaded in poly(HEMA‐MAA) copolymeric particles were carried out in fasted diabetic rats and highest decrease in blood glucose level from 506 mg/dL to 170 mg/dL was observed within first 3 h. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Synthesis and physico‐chemical properties of novel dialkyl diphosphate gemini surfactants based on octadecanol

A series of dialkyl diphosphate gemini surfactants has been synthesized using C₁₈ as hydrophobic chains and phosphate as head groups. Three flexible spacers have been used. In the present study, an attempt has also been made to synthesize mono octadecyl phosphate (MOP) at 35°C, which was used as an intermediate in the synthesis of geminis. This long chain of MOP has been effectively converted to gemini surfactants and subsequently converted to their disodium salts. The effect of reaction variables like temperature, duration, molar ratios of reactants, catalyst and spacer on the yield of dialkyl diphosphate gemini surfactant has also been reported. The MOP, gemini surfactants and disodium salt of gemini surfactants were characterized using FT‐IR and ¹H‐NMR. Surface active and physico‐chemical properties of synthesized gemini surfactants and their monomer were also determined. The results revealed that the yield of dialkyl diphosphate gemini surfactants ranged from 80 to 90%. Among all synthesized dialkyl diphosphate gemini surfactants D, S‐1,6‐GSOD had maximum anionic content, i.e. 80.7%, showed highest foaming ability and superior dispersing ability, whereas D, S‐1,8‐GSOD showed low cmc values, i.e. 0.00012 mM/L; minimum surface tension and interfacial tension, i.e. 39.1 and 36.3 mN/m, respectively.     

The kinetic study for asymmetric membrane formation via phase-inversion process

The kinetics of membrane formation by phase inversion was studied emphasizing the rate of solvent diffusion from a polymer solution during the phase separation. Diffusional behavior of the solvent can be considered Fickian. Membrane morphologies were shown to be strongly dependent on the rate of solvent diffusion, indicating that mass-transfer rates of solvent and nonsolvent during phase separation are crucial for determining the final membrane structure for the following system: polysulfone (polymer), dimethyl acetamide (solvent), and ethanol (gelation medium). Specific reference to the mechanism of macrovoid formation was explored. Macrovoid formation was found to be proportional to the square root of time, suggesting that it is governed by a diffusion process. In addition, latex particles of coagulated polymer formed by the nucleation and growth of a concentrated polymer phase was observed inside the macrovoids. Such a result implies that the macrovoids grow by a diffusive flow which results from the growth of the polymer lean phase during binodal decomposition. © 1996 John Wiley & Sons, Inc.     

POSSIBILITY OF CONCENTRATION POLARIZATION OCCURRING INSIDE THE MEMBRANE DURING STEADY STATE PERVAPORATION

Mathematical equations are derived for describing the pervaporation transport of pure penetrant through polymeric membranes by assuming the chemical potential gradient as the driving force for the flow of penetrant. An imaginary phase (liquid or vapor) is assumed to be present and is in thermodynamic equilibrium with the membrane phase for deriving these equations. The mathematical equations obtained are similar to those derived by Okada and Matsuura (1991) using the pore-flow model. The possibility of concentration polarization occurring inside the membrane is predicted based on the analysis of binary mixture pervaporation. Experimental profiles of binary penetrant concentration in the membrane are established and these profiles substantiate the prediction of concentration polarization occurring inside the membrane. Pervaporation and sorption data from liquid and vapor phase at 25° C are reported for the acetic acid-water-polyamide system.     

Polymer-polymer interaction parameter determined by inverse gas chromatography

Inverse gas chromatography was employed to determine the apparent polymer-polymer interaction parameter χ′_23,app for the following blends using them as binary stationary phases: poly(vinyl acetate)-poly(n-butyl methacrylate) at 100 and 120°C, poly(vinyl acetate)-atactic poly(vinyl isobutyl ether) at 70°C, and poly(n-butyl methacrylate)-atactic poly(vinyl isobutyl ether) at 70°C. The interaction parameter χ′_23,app depended significantly on the chemical nature of the solvent (probe) used and the composition of the stationary phase. The lowest values of χ′_23,app were obtained when aromatic and chlorinated-alkane probes were eluted on stationary phases having weight fractional compositions of the component polymers in the range 0.4–0.6. The results predict a better compatibility for poly(n-butyl methacrylate)-atactic poly(vinyl isobutyl ether) than for the other blends.     

Inverse gas chromatography of poly(vinylisobutyl ethers) and polymer-solute thermodynamic interactions

Gas chromatography (GC) retention behavior of atactic and isotactic poly(vinylisobutyl ether) stationary phases has been studied in the temperature range 30–90°C using 16 solutes which include various alkanes, alkylbenzenes, and chlorinated aliphatic hydrocarbons. The bulk sorption equilibrium retention data have been employed to derive various thermodynamic quantities at infinite dilution of solutes in the polymers, viz., χ, χ^*, χ_H, χ_S, X₁₂, δH_S, h . Their dependence on temperature, polymer structure, and chemical nature of solutes has been discussed.     

Inverse gas chromatography of poly(n-butyl methacrylate): Effect of flow rate on specific retention volume and detection of glass transition temperature

Flow-rate effect on specific retention volume (V) was studied by eluting aliphatic, aromatic, and chlorinated aliphatic probes at infinite dilution on poly(n-butyl methacrylate) stationary phase at different temperatures from ?10 to 150°C, encompassing both the glass transition (T_g) and the softening temperatures of the polymer. The effect became pronounced as the temperature was reduced below 100°C. V decreased with an increase in the flow rate: first linearly at temperatures between 70 and 100°C, and then nonlinearly at all temperatures below 70°C. The retention diagrams of n-pentane, isooctane, and cyclohexane alone enabled the detection of glass transition. Dichloromethane gave a linear retention diagram through T_g without showing the flow-rate effect.