Interaction of nitrophenols with lipids at the air/water interface.

The uptake of ortho and para nitrophenol to charged and neutral lipid monolayers spread at the air/solution interface was studied by reflection spectroscopy. The adsorption characteristics of the two nitrophenols have been studied by measuring the surface pressure and surface potential as a function of molecular area of the different lipid monolayers in the presence of nitrophenols in the subphase. The results have been interpreted in terms of the electrostatic interaction between the negatively charged dissociated phenolate ions and the positively charged head group of dioctadecyldimethylammonium bromide monolayers

Two-dimensional surface properties of 2-methoxy ethyl oleate at the air/water interface

Methoxy ethyl oleate, a nonionic surfactant, has been investigated at the air/water interface for various surface properties by employing the Langmuir film balance technique. The ester forms an expanded isotherm at the air/water interface. The minimum area of packing (A0), initial area of increase of surface pressure (Ai), collapse pressure (πc), and area/molecule at collapse pressure (Ac) have been estimated from the isotherm curve. The higher compressibility coefficient (K) suggests that the ester forms a more expanded liquid film than the parent oleic acid. Besides, the ester film is fairly stable as suggested by only about 30% loss in area over a period of 20 min. The relaxation rates of the ester film at different surface pressures of 10, 15, and 20 mN.m-1 have been estimated from changes in the surface area/molecule with time. Interestingly, the surface area (54.2 Å2/molecule) that corresponds to a minimized structure projected for the ester, calculated theoretically, agrees reasonably well with the experimental value (57.2 Å2/molecule)

Comparative Studies on Effect of Cationic and Anionic Finishing Agents on Surface Property of Finished Leather

Content: The present work attempts to analyze the surface and physical properties of leathers finished with cationic and anionic finishing chemicals. The contact angles of liquid drops resting on the leather surface have been used to evaluate surface energy, acidity, basicity components of the surface energy, polarity and work of adhesion. Contact angle values have been measured for chrome tanned and conventionally retanned crust and finished leather made by varying pigment and binder combinations. The wettability of finished leather has been correlated with the contact angle values: the higher the contact angle value the lesser is the wetting observed. Complete wetting can be obtained when the contact angle value is zero i.e. the drop of liquid spreads spontaneously on the surface and partial wetting is obtained when the contact angle value is in between 0and 900. Acrylic binders with different film forming properties, protein, polyurethane and butadiene binders have been combined to prepare different finish formulations.The results have been correlated with wet and dry rub fastness, finish adhesion, vamp flexing value, water vapour permeability and water proofness. It has been observed that when the surface of leather is coated with acrylic binder the contact angle value due to polar solvents(water) , non polar solvents(hexadecane) and moderately polar (DMSO) and methyl iodide show that as the thickness of coating increases, the contact angle value decreases for the base coat and sharply increases when top coat is applied. Top coats have the ability to increase the contact angle and they improve the performance properties of leather such as water resistance, fastness, finish adhesion etc. Cationic and anionic finishing formulations have been compared to study their effect in modifying the surface of finished leather based on contact angle values, wet and dry fastness to circular rubbing and water resistance. It has been observed that leathers finished using anionic finishing technique shows better wet rub fastness and water resistance effect compared to cationic finishing technique. Take-Away: The effect of number of top coats on water contact angle value were determined ,and the experiment showed that the value were decreased gradually at the beginning of the coat because the top coats are water based so during the coating process the hydrophobic nature of the surface of chrome tanned leather have decreased. The experimental result from contact angle value showed that coating with pigments and binders have increased the contact angle value compared to the control crust. It has been observed that leathers finished using anionic finishing technique shows better wet rub fastness and water resistance effect compared to cationic finishing technique

Hydrogen storage in carbon nanotubes and related materials

Adsorption of hydrogen at 300 K has been investigated on well-characterized samples of carbon nanotubes, besides carbon fibres by taking care to avoid many of the pitfalls generally encountered in such measurements. The nanotube samples include single- and multi-walled nanotubes prepared by different methods, as well as aligned bundles of multi-walled nanotubes. The effect of acid treatment of the nanotubes has been examined. A maximum adsorption of ca. 3.7 wt% is found with aligned multi-walled nanotubes. Electrochemical hydrogen storage measurements have also been carried out on the nanotube samples and the results are similar to those found by gas adsorption measurements

Control of interfacial equilibria by local charge distribution and average surface potential.

http://dx.doi.org