摘要:

The properties of Langmuir layers made up of three bola-ampbiphiles having the general structure UA-Cn-UA, where UA denotes urocanic acid and Cnis an alkyl chain of varying length (n = 8, 12 and 16) and of a monopolar amphiphile (UAC12) were investigated. The area per molecule at the air-water interface was measured. Moreover, a modeling study was performed to visualize the conformation of these compounds at the air / water interface. The pressure-area isotherm and the molecular modeling study indicate that a folded conformation is possible only for the UAC16UA bola-amphiphile. This result could be connected to the ability of UAC16UA to form micelles.

ISSN:0193-2691    

DOI:10.1080/01932699908943870

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The effect on the electrical properties of polymethylmethacrylate polymer containing liquid crystal as dispersed molecules is investigated in the temperature range 30-100°C and the frequency ange from 100 Hz to 10 kHz. It is found that increasing the liquid crystal content enhances the ac-impedance, decreases the ac-loss conductivity and decreases the value of the dielectric constant. The decrease in the ac-impedance with increasing frequency is associated with a dramatic increase in the ac-loss conductivity at frequencies higher than 1 kHz. The decrease in the ac-conductivity with increasing the dispersed liquid crystal phase is attributed to the reduction of the mobility of the charge carriers. Thus, the dielectric property of the system improves.

ISSN:0193-2691    

DOI:10.1080/01932699908943871

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A spectrophotometric method with an attachment made by ourselves was used to measure the transition temperatures (TJL) from aqueous solution into lyotropic liquid crystalline phase of potassium myristate (KMy). The transition process was shown clearly by an absorbance, A, vs. temperature, T, curve. TIL was obtained from the intersection point of two curves on a plot of δA / δT vs.T¯ TJLmeasured by our method can be compared with reported data. The solubilization of small amounts of inorganic (potassium oxidate) or organic (diphenyl ketone) additive can shift the transition temperature, and TJLrose with increasing concentration of additive. Potassium oxidate or diphenyl ketone in KMy-H2O system made the system form a lamellar liquid crystal instead of the original hexagonal liquid crystal, which was considered to relate to increase of the TJL.

ISSN:0193-2691    

DOI:10.1080/01932699908943872

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The formation of silver nanoparticles by the method of reduction of silver ions by sodium borohydride in non-ionic water-in-oil microemulsion was investigated as a function of structure of the surfactant. Three types of non-ionic surfactants were selected differing in the chain length of the oxyethylene groups for example: NP-5, NP-9 and NP-11. The silver nanoparticles were characterized by UV-Visible Absorption Spectroscopy and Transmission Electron Microscopy. TEM. The results of this study showed that the panicle size is relatively smaller incase of NP-9 while for NP-5 and NP-11 the sizes are comparable. This obsevation is explained on the basis of structure of the droplets and the influence of Intermicellar exchange on nucleation and growth of particles.

ISSN:0193-2691    

DOI:10.1080/01932699908943873

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A ternary complex kinetic model for metallomicellar catalysis has been proposed in this paper. Hydrolysis of PNPP influenced by Co-micelles of long alkyl-pHridines with hydroxyl groups and CTAB was investigated in aqueous buffers of pH ranging from 5. 0 to 7. 0 at 30°C at present of Cu2+. The kinetic and the thermodynamic parameters (Kn', Km', KT) were obtained by the kinetic analyses,moreover,the rate constant Knin metallomi-cellar phase was obtained. The pKϵs of the hydroxyl groups of these complexes were determined to be 5. 62,5. 53,5. 34,5. 32,respectively by analyses of pH-rate profiles. The results indicate that pyridine ligands exhibit a great catalysis on the hydrolysis of PNPP,which increases with increasing the hydrocarbon chain length.

ISSN:0193-2691    

DOI:10.1080/01932699908943874

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Water/TX-100/Hexanol/Octane reverse microemulsions were investigated by Microcalorimetry and FT-IR. Experiments show that the formation of this reverse microemulsion is an exothermic process, and it's a two-step reaction. The first step is action of TX-100 monomers with water to form hydrogen bond while the second is interaction between polyethylene oxide groups in reverse micelles and water. The characterizations of FT-IR and Microcalorimetry indicate that aqueous core of the microemulsion droplets are composed of bound and free water while a small amount of trapped water, OH stretching vibration peak of bound water, free water, and trapped water are at 3400 ±20 cm−1, 3220 ± 20 cm−1, and 3550 ± 20 cm−1respectively. Polyethylene oxide ether of TX-100 is prior to phenyl ether in acting with water because its polarity is stronger than phenyl ester.

ISSN:0193-2691    

DOI:10.1080/01932699908943875

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Silicas were obtained using a precipitation technique from metasilicate solution with an acidic agent. The precipitation process includes formation of silica particles and their aggregation.

ISSN:0193-2691    

DOI:10.1080/01932699908943876

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We used the radiosoptopic tracer and HPLC to measure the concentration of nonionic surfactants, petroleum sulfonate and polyacrylamide respectively,and studied the effect of petroleum sulfonate.polyacrylamide, black liquor, and black liquor system on distribution and diffusion of nonionic surfactants in the system of toluene and water, and tbe effect of nonionic surfactants on the distribution of petroleum sulfonate and polyacrylamide with different temperature. It was found that petroleum sulfonate mainly existed in the oil phase.polyacrylamide was quite the contrary, the existence of black liquor system and its components decreased both diffusion rates and partition coefficients of nonionic surfactants and the distribution of ic surfactants and the distribution of nonionic surfactants was different with the variation of HLB and temperature.

ISSN:0193-2691    

DOI:10.1080/01932699908943877

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The influence of surfactant / polymer (polyethylene glycol, PEG, mol. wt. = 400) mixtures upon the acidic hydrolysis of two N-substituted hydroxamic acids, i.e., R(CO). N(OH)R' : R = C6H5, R' = C6H5;4-CH3C6H4has been studied using cationic (CTAB, TTAB and CPC) and nonionic (TX-100 and Brij-35) surfactants. An inhibitory effect was observed. The results have been explained by Porinoy - Menger model. The critical aggregation concentration and polymer saturation point of the corresponding systems have also been measured with the conductivity and surface tension methods.

ISSN:0193-2691    

DOI:10.1080/01932699908943878

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Monodisperse microspheres of polystyrene with diameters in the size range I -2.2(μm) were prepared by the radiation-induced dispersion polymerization. The polystyrene microspheres by radiation-induced in the presence of co- solvent (DMSO-H2) was investigated as functions of various factors such as irradiation time, irradiation dose rate, the amount of water and on or not stirring et al. The number of the nuclei produced in the early stage of the polymerization was found to be constant during the remainder of the polymerization. The nuclei grow to be monodisperse polymer particles without aggregation under appropriate conditions, This is attributed to the low mobility of the growing polymer particles.

ISSN:0193-2691    

DOI:10.1080/01932699908943879

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor