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33.
Johan Sjöblom Hege Ebeltoft Alf Bjørseth Stig E. Friberg Chris Brancewicz 《Journal of Dispersion Science and Technology》2013,34(1):21-34
Hydrolysis and condensation of monomolecular alkyloxysilane films by the Langmuir technique is presented. Octadecyltrimethoxysilane formed monolayers on aqueous subphases with different properties depending on the bulk pH. At pH 1 a solid condensed film was directly formed with a molecular area of 23 Å2 and a surface pressure/surface area variation similar to that on non-ionized stearic acid. At pH 5.6 and 11 several phase transitions were observed during the compression of the monolayer with a final collapse at a molecular area of 20 Å2. Relaxation measurements confirmed the stability of the films for longer than 12 hours at different surface pressures below a critical value. 相似文献
34.
Stig E. Friberg Ibrahim Kayali Tatang Suhery Linda D. Rhein F. Anthony Simion 《Journal of Dispersion Science and Technology》2013,34(3):337-347
Water uptake in natural and reaggregated stratum corneum was determined by weight difference after storage in an atmosphere of controlled relative humidity. Interlayer spacing in separated lipids as a function of their water content was determined by low-angle X-ray diffractometry. These values were used as a calibration curve to determine the water content of the lipid bilayers in reaggregated stratum corneum. The results revealed different behavior of the lipid models compared to natural lipids of the stratum corneum. The additional water taken up after reaggregation of equilibrated lipids and proteins, was equally partitioned between the protein and the natural lipid fraction, while the models gave a proportionally higher water uptake into the lipids at high relative humidity. It is obvious that the models, so far, do not mimic all the properties of the natural stratum corneum lipids. 相似文献
35.
Stig R. Erlander 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):1181-1193
Abstract Previous developed theories were applied in explaining the mechanism for the salting-in and -out of various amino acids. Glycine is salted-in according to the cationic sequences Li+ > Na+ > K+ > Rb+ and Ca2+ > Ba2+ > Sr2+. The ability of a cation to increase the solubility of an amino acid therefore corresponds to the destruction of the ion-ion bond between the - CO-2and the -NH+ 2group of the amino acid by forming an insoluble ion-ion bond between the added cation and the - CO?2 group. This insolubilizing effect produces a positive charge on the amino acid. If, however, the anion of the added salt forms a relatively insoluble ion-ion bond with the -NH+2 group of the amino acid, then the effect is minimized because now both charges on the amino acid are reduced. Consequently, the more insoluble the cation amino acid salt and the more soluble the anion amino acid salt (or vice versa), the greater will be the salting-in effect. Titration of either charged group on the amino acid zwitterion has the same effect, since now the ion-ion bond of the amino acid is again destroyed. Aliphatic and carboxylic acid groups also effect the salting-in sequence, since these groups are salted-out by addition of salt when D± < DH2o. These mechanisms explain how leucine is first salted-out, then salted-in (at 4 M) and finally salted-out again (at 9 M) in LiCl solutions. Urea salts-in hydrophobic amino acids by increasing the dielectric constant and salts-out polar amino acids by increasing the interaction between the two charge groups on the amino acid. Glycine reverses the salting-in effect of NaCl on asparagine by competing for the Na+ ion. 相似文献
36.
The equilibrium topology of an aqueous Janus emulsion of two oils, O1 and O2, with water, W, [(O1+O2)/W], is numerically evaluated with the following realistic interfacial tensions (γ): γO2/W=5 mN m−1, γO1/O2=1 mN m−1, and γO1/W varies within the range 4–5 mN m−1, which is the limiting range for stable Janus drop topology. The relative significance of the two independently pivotal factors for the topology is evaluated, that is, the local equilibrium at the line of contact between the three liquids and the volume fraction of the two dispersed liquids within the drop. The results reveal a dominant effect of the local equilibrium on the fraction of the O2 drop surface that is covered by O1. In contrast, for a constant volume of O2, the impact of the interfacial tension balance on the limit of the coverage is modest for an infinite volume of O1. Interestingly, when the O1 volume exceeds this value, an emulsion inversion occurs, and the O1 portion of the (O1+O2)/W topology becomes a continuous phase, generating a (W+O2)/O1 Janus configuration. 相似文献
37.
Stig E. Friberg 《Journal of Dispersion Science and Technology》2013,34(1):9-16
The evaporation path in a microemulsion base of water, sodium dodecylsulfate, and pentanol was extended to include the subsequent precipitation stage caused by the restriction of the surfactant solubility. The results revealed the surfactant to be the only compound to precipitate during the evaporation/precipitation stage; the relative content of the two volatile compounds in the liquid phase was adjusted to the required level by the evaporation. 相似文献
38.
Stig E. Friberg 《Journal of Dispersion Science and Technology》2013,34(2):207-212
The evaporation paths in a system of three single‐compound phases in equilibrium were calculated using a phase diagram approach assuming the evaporation rate proportional to the compound's vapor pressure and molecular weight. The variation with time of the weight of the individual phases was linear, while the weight fraction was not. The approach allowed a simple calculation of the fraction of remaining compounds after one of them was exhausted during the evaporation and a convenient graphical illustration of the importance of the relative vapor pressures. 相似文献
39.
Jun Yang Rong Guo Stig E. Friberg 《Journal of Dispersion Science and Technology》2013,34(3-4):249-261
Addition of alcohol with longer chain length (C6H13OH, C8H17OH, and C12H21OH) caused a reduction the cloud point of a commercial nonionic surfactant, Tesgitol (T15-s-9). The formation of lamellar liquid crystal (LLC) was favored so that isotropic liquid (L1)-LLC two-phase region became wider with increasing temperature at an appropriate weight ratio of surfactant to alcohol. The isotropic liquid phase/liquid two phase transformation was replaced by a two-phase transformation to isotropic liquid/lamellar liquid crystal at the cloud point for the system without alcohol. 相似文献
40.
Abeer Al-Bawab Ayat Bozeya Stig E. Friberg Patricis A. Aiken 《Journal of Dispersion Science and Technology》2013,34(5):606-610
The phase diagram of fragrance oil, geranyl acetate, water, and a surfactant, Laureth 4, was used to calculate the surfactant association structures present in emulsions with constant O/W ratio for increased fractions of surfactant. The liquid crystal appeared in the emulsion at a critical value of the surfactant fraction and additional surfactant caused an approximately linear increase of it, while the fraction of the aqueous phase experienced a corresponding reduction. The result of the calculations was confirmed by optical microscopy observation with the samples between crossed polarizers. The calculations revealed the formation of vesicles from the liquid crystal to result in a drastic reduction of the “free” aqueous phase, due to the amount of the aqueous liquid forming the core of the vesicle. 相似文献