Diffusion of linear aliphatic esters in polyethylene as a function of chain length of the esters,pressure and temperature

Diffusion of linear aliphatic mono- and diesters (C _N ) havingN main chain atoms (N=13–68) in bulk medium-density polyethylene (MDPE) has been studied under hydrostatic pressures up to 2500 bar at temperatures between 60°C and 125°C. Three triglycerides, phenyl stearate, and p-aminoazobenzene (pAAB, 80°C) as the diffusants and low-density (LDPE) and high-density (HDPE) polyethylenes as polyethylene substrate were used for comparison. Diffusion coefficientD was determined from concentration distribution of the diffusants through stacked PE sheets as substrate. Regarding the linear esters at 90°C, the relationshipD N holds at constant pressures. Under the atmospheric pressure, became –2.10 in accordance with de Gennes's proposal (1971)D N ^–2 as well as with the experimental results reported by Klein and Briscoe (1979) forN larger than 30.D's for the glycerides deviate from the relationshipD N ^–2 toward the smaller values by comparison at the sameN. The exponent is pressure-dependent. It decreases with increasing pressure according to =–2.10–0.000942P, whereP is measured by the unit of bar. Plots of lnD vsP for all the diffusants show linear relationships with negative slopes, from which activation volume for the diffusion V was calculated. At 90°C, V increases slowly with increasingN and increasingV _Ki, the intrinsic molecular volume of the diffusant, from 39.3 cm³/mol for ethyl caprate (C ₁₃,V _Ki=136 cm³/mol) to 76.8 cm³/mol for behenyl behenate (C₄₅,V _Ki=466 cm³/mol). Observed V s are explainable on the basis of the reptation mode of the chain molecule diffusion. V s for C₂₅ and C₄₅ are found to increase with increasing degree of crystallinity where MDPE, heat-treated MDPE, LDPE, and HDPE were used. The results obtained by varying temperature are as follows. V for C₄₅ was always found to be larger than C₂₅. Both decreased linearly with increasing temperature, giving two linear lines with different slopes whose extensions intersected at 132°C, the melting point of the MDPE, where the difference in V disappeared. The apparent activation energiesE _Ds for the diffusion of C₂₅ and C₄₅ increased linearly with increasing pressure, whose slopes are explainable according toE _D=E ₀+PV [1-(dln V /dlnT) _P ].     

A specific bio-electrochemical sensor for hydrogen peroxide

A bio-electrochemical sensor specific for hydrogen peroxide is described. The sensor consists of two membranes—a catalase-collagen membrane and a teflon membrane—an alkaline solution, a platinum cathode and a lead anode. The catalase-collagen membrane is prepared electrochemically, the thickness being 1 μ; the enzyme activity is similar to that of native catalase. The sensor responds to hydrogen peroxide with a response time of only 1–2 min. The calibration curve is quite linear over a concentration range of 0–1.5 mmol l^-1 for hydrogen peroxide. The utility of the sensor in continuous usage is discussed.     

Sol-Gel Formation of ITO Thin Film from a Sol Including ITO Powder

Recently, low temperature synthesis of ITO thin film of low resistivity is desired in the field of LCD (Liquid Crystalline Display) production. This paper describes the results of experiment to produce ITO thin film from a sol containing crystalline ITO particles and alkoxides of In and Sn. Crystallization temperature of ITO thin film obtained from the sol mixed with ITO powder was lower than that of ITO from the sol without ITO powder. Furthermore, the resistivity of the former ITO thin film was lower than that of the latter. It was assumed that these results were attributed to the promotion effect of ITO crystalline particles to crystalize the amorphous ITO gel at lower temperature. This low temperature crystallization effect plays an important role in enhancing the crystallinity and electric conductivity of ITO thin film from sol-gel process.     

Ultraviolet-Laser-Induced Crystallization of Sol-Gel Derived Indium Oxide Films

Modification of sol-gel derived indium oxide thin films using ultraviolet lasers was investigated. Irradiation by an ArF excimer (6.4 eV) and the fourth harmonic generation of a Nd : YAG laser (4.7 eV) was found to be effective in crystallization with a loss of hydroxyl groups and a decrease in the sheet resistance of the sol-gel films. Transparent crystalline indium oxide films were successfully obtained by 6.4 eV laser irradiation at fluences below 20 mJ/(cm2·shot), whereas degradation of the films was induced by a relatively high-fluence beam.     

Simultaneous determination of In(III) and Cd(II) by differential pulse polarography in the presence of poly β-cyclodextrin

The difference in the peak potentials of In(III) and Cd(II), whose reduction potentials are very close to each other, becomes large in the presence of poly beta-cyclodextrin in sodium perchlorate medium. The relationships between the peak currents for these two ions and their concentrations are linear, suggesting that the simultaneous determination of the ions is possible in the presence of this reagent.     

Synthesis of polypyridazinophthalazinediones from dibenzoylphthalic acids and aromatic dihydrazines

A novel class of polypyridazinophthalazinediones has been synthesized by the solution cyclopolycondensation in m-cresol of dibenzoylphthalic acids with aromatic dihydrazines such as bis(4-hydrazinophenyl)methane and bis(4-hydrazinophenyl) sulfone. The polyheterocycles derived from 4,6-dibenzoylisophthalic acid, which had inherent viscosities of up to 0.5, were soluble in m-cresol and hot dichloroacetic acid, whereas the polymers from 2,5-dibenzoylterephthalic acid were practically insoluble in organic solvents. Thermogravimetric analyses showed that all the polymers underwent weight losses of 10% at 490–520°C in both air and nitrogen.     

Use of Side‐Chain Incompatibility for Tailoring Long‐Range p/n Heterojunctions: Photoconductive Nanofibers Formed by Self‐Assembly of an Amphiphilic Donor–Acceptor Dyad Consisting of Oligothiophene and Perylenediimide

To tailor organic p/n heterojunctions with molecular‐level precision, a rational design strategy using side‐chain incompatibility of a covalently connected donor–acceptor (D–A) dyad has been successfully carried out. An oligothiophene–perylenediimide dyad, when modified with triethylene glycol side chains at one terminus and dodecyl side chains at the other ( 2 Amphi ), self‐assembles into nanofibers with a long‐range D/A heterojunction. In contrast, when the dyad is modified with dodecyl side chains at both termini ( 2 Lipo ), ill‐defined microfibers result. In steady‐state measurements using microgap electrodes, a cast film of the nanofiber of 2 Amphi displays far better photoconducting properties than that of the microfiber of 2 Lipo . Flash‐photolysis time‐resolved microwave conductivity measurements, in conjunction with transient absorption spectroscopy, clearly indicate that the nanofiber of 2 Amphi intrinsically allows for better carrier generation and transport properties than the microfibrous assembly of 2 Lipo .     

Determination of antihyperglycemic biguanides in serum and urine using an ion-pair solid-phase extraction technique followed by HPLC-UV on a pentafluorophenylpropyl column and on an octadecyl column

An HPLC-UV method was established for the determination of metformin and buformin in biological fluids. Metformin was not retained on particles packed in conventional solid-phase extraction cartridges; in contrast, buformin was retained too firmly and not eluted with a solvent for recovery. However, both drugs were retained on particles that had been treated with an ion-pair reagent of heptanesulfonate or dodecylsulfate and recovered almost completely. The recovered fraction was subjected to HPLC on a pentafluorophenylpropyl column which was suitable for the determination of both biguanides in serum and in urine. Limits of quantitation were low enough for clinical use, and reproducibility was high with an RSD of 0.9-2.3%. HPLC on a conventional octadecyl column was suitable only for the determination of buformin in serum since interfering peaks appeared on the chromatograms of urine samples. The method was applied to analysis of some clinical specimens.