Fabrication of Zeolite A Rods with Irregular Macropores by Self-assembly of Zeolite A Microcrystals Using Microwave-assisted Hydrothermal Synthesis

Zeolite A rods by self-assembly of zeolite A microcrystal were successfully synthesized by microwave-assisted hydrotherrnal synthesis. The average size of zeolite crystals consisting of self-assembling materials was about 300 nm and the length of zeolite rods was in the range of 15--30μm.     

Sels de N-alcoxyquinoléinium et de N-alcoxyisoquinoléinium porteurs d'une fonction ester dans leur chaine alcoxyle: Synthèse et réactivité vis-a-vis des ions cyanure

Reaction of ethyal α-bromoisobutyrate on quinoline 1-oxide and isoquinoline 2-oxide in the presence of silver perchlorate leads to the corresponding N-alkoxyl salts 1 and 2 . On treatment with potassium cyanide, these salts are converted into 2-cyanoquinoline and 1-cyanoise-quinoline according to mode B of the Katritzky' s classification concerning the reaction of nucliophiles on N-alkoxypyridinium salts. When the reaction of cyanide ions were performed on salt 1 at 0° in aqueous solution the dihydro aromatic 4 was isolated. This result confirms the addition-elimination mechanism of the reaction studied.     

Dimeric and oligomeric surfactants. Behavior at interfaces and in aqueous solution: a review

Dimeric and oligomeric surfactants are novel surfactants that are presently attracting considerable interest in the academic and industrial communities working on surfactants. This paper first presents a number of chemical structures that have been reported for ionic, amphoteric and nonionic dimeric and oligomeric surfactants. The following aspects of these surfactants are then successively reviewed the state of dimeric and oligomeric surfactants in aqueous solutions at concentration below the critical micellization concentration (cmc); their behavior at the air/solution and solid/solution interfaces; their solubility in water, cmc and thermodynamics of micellization; the properties of the aqueous micelles of dimeric and oligomeric surfactants (ionization degree, size, shape, micropolarity and microviscosity, solution microstructure, solution rheology, micelle dynamics, micellar solubilization, interaction between dimeric surfactants and water-soluble polymers); the mixed micellization of dimeric surfactants with various conventional surfactants; the phase behavior of dimeric surfactants and the applications of these novel surfactants.     

Micellization and adsorption of a zwitterionic surfactant: N-dodecyl betaine-effect of salt

Time-resolved fluorescence quenching, self-diffusion measurements and calorimetric investigations have been used in order to investigate the effect of salt on aggregation in aqueous solutions and the adsorption onto silica gel of the zwitterionic surfactant N-dodecyl betaine (NDB).

The micelle aggregation number of NDB stays constant when the NDB or salt concentration increases but decreases with an increase of temperature. Evidence is presented for the binding of cations and anions to micellar aggregates. The degree of binding has been obtained for Na⁺, Ca²⁺ and Cl⁻ ions; it is always larger for the anion.

Enthalpies of micellization were obtained directly from calorimetric curves of NDB in dilution experiments. The observed decrease of the endothermic enthalpies of micellization with increasing temperature or salinity is attributed to a structural change in the water molecules around the alkyl chain of the free monomers.

The adsorption isotherms of NDB onto silica gel depend very little on temperature, and a plateau is reached near the CMC. At saturation, the adsorbed amount of NDB depends on the salt and follows the sequence NDB < (NDB + NaCl) < (NDB + CaCl₂).

The exothermic differential molar enthalpies of adsorption demonstrate the same behaviour as the enthalpies of micellization with varying temperature or salinity. Adsorption onto silica gel depends on the NDB concentration, the salt concentration and temperature.     

Alkanediyl-alpha,omega-bis(dimethylalkylammonium bromide) surfactants 9. Effect of the spacer carbon number and temperature on the enthalpy of micellization

The enthalpies of dilution of micellar solutions of several 12-s-12 dimeric surfactants of the alkanediyl-alpha,omega-bis(dodecyldi-methylammonium bromide) type, differing by the carbon number s of the alkanediyl spacer, and of dodecyltrimethylammonium bromide (DTAB) have been measured calorimetrically, in a range of concentrations extending from well below to well above the critical micelle concentration (cmc). The results permitted the determination of the enthalpy of micellization, DeltaH degrees (M), of the investigated surfactants at 25 and 35 degrees C. The values of DeltaH degrees (M) were always negative and became more negative as the temperature was increased. The plot of -DeltaH degrees (M) against s showed a shallow minimum at about s=5 and a large decrease of -DeltaH degrees (M) going from 12-2-12 to 12- 4-12. This effect has been attributed to the contribution to DeltaH degrees (M) of the hindered rotation of the dodecyl chains around the spacer C-C bond for 12-2-12. This hindrance is shown to rapidly disappear when s is increased from 2 to above 4. The specific heats of micellization, the free energies of micellization, and the entropies of micellization (DeltaS degrees (M)) have been calculated using the DeltaH degrees (M) values and the reported cmc and micelle ionization degree data for 12-s-12 surfactants and DTAB. For all surfactants the results show that TDeltaS degrees (M)>-DeltaH degrees (M), indicating an entropy-driven micellization.     

Density and ultrasonic absorption studies of the interaction between polyions and hydrophobic counterions

The volume changes associated with the interaction between tetra-n-propylammonium, propylammonium and butylammonium ions with the polyethylenesulphonate ion (PES) have been determined from density measurements. The excess ultrasonic absorption of solutions of PES and polystyrenesulphonic (PSS) acids has been measured as a function of the neutralization degree by tetramethylammonium (TMA) and tetra-n-butylammonium (TBA) hydroxides. The results confirm that a negligible volume change is associated with the interaction between tetramethylammonium ions and polyions. They indicate that the interaction of large tetraalkylammonium (TAA) ions with polyions gives rise to a small contraction. This effect may be due to [1] disruption of the organisation of the water molecules about the TAA ion alkyl chain when the chains come close enough to polyion charged sites, under the effect of the electrical charges; [2] to enhanced TAA-TAA interactions in the neighbourhood of polyions, owing to the so-called condensation phenomenon; and [3] to hydrophobic interactions between TAA ions and polyions, in the case of hydrophobic polyions such as PSS.     

Partial molal volumes of ions in organic solvents from ultrasonic vibration potential and density measurements. III. Dimethylsulfoxide

The partial molal volumes of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Cl^–, Br^–, I^–, and NO ₃ ^- in DMSO at 25°C have been determined from ultrasonic vibration potential data and density data for solutions of uni-univalent electrolytes. Hepler's semiemprirical equation has been used to split ionic partial molal volumes into geometric and electrostrictive contributions. The results obtained in this work confirm the conclusion of our previous studies, namely, that the contribution of electrostriction is essentially determined by the properties of that layer of atoms, 0.3 to 0.4 nm thick, in contact with the ion and by the degree of steric hindrance of the poles of the dipole of the solvent molecule. On the other hand, the geometric contribution depends on the size of the solvent molecule and also on the arrangement of the solvent molecules about the ions. It is shown that the geometric contribution to the partial molal volume of ions is largely increased when ions cannot come close enough to the poles of the solvent-molecule dipole, owing to steric hindrance.     

A disposable biosensor for the determination of alpha-amylase in human saliva

A disposable tri-enzymatic biosensor is presented for the determination of α-amylase in human saliva. It is based on the quantity of maltose generated by hydrolysis of maltopentose in the presence of salivary α-amylase. The biosensor is fabricated by co-immobilization of the enzymes α-glucosidase, glucose oxidase, and mutarotase on screen-printed electrodes modified with Prussian Blue. The assay can be performed with a “drop” of sample, this allowing for ease and simplicity. A linear relationship is found for the range from 5 to 250 units per mL, with an LOD of 5 units per mL. The biosensor is stable for at least one month and over this time retains 80% of its original activity. The system was then evaluated for matrix effects of human saliva and compared to a spectrometric method using a commercially available kit.