Surface tension, studying

At this stage in the literature, there is no method available by which one can directly determine the orientation of molecules of liquids at interfaces. Molecules are situated at interfaces (e.g., air-liquid, liquid-liquid, and solid-liquid) under asymmetric forces. Recent studies have been carried out to obtain information about molecular orientation from surface tension studies of fluids (Birdi, 1997). It has been concluded that interfacial water molecules, in the presence of charged amphiphiles, are in a tetrahedral arrangement similar to the structure of ice. Extensive studies of alkanes... 

These data are useful since water is used as a calibration liquid in many surface tension studies. 

Wangsakan, A., Chinachoti, P., McClements, D.J. (2001). Maltodextrin-anionic surfactant interactions isothermal titration calorimetry and surface tension study. Journal of Agricultural and Food Chemistry, 49, 5039-5045. 

R = mean radius of the tensiometer ring used in the surface tension studies,... 

M.J. Schick, Surface films of nonionic detergents, I, Surface tension study, J. Colloid Sci. 17 (1962) 801-813. 

Wulf, M., Uhlmann, P., Michel, S., and Grundke, K. (2000), Surface tension studies of levelling additives in powder coatings, Prog. Org. Coat., 38,59-66. 

Surface tension studies of the most common fluorosilicone, poly(3,3,3-trifluoropropylmethylsiloxane) (PTFPMS), give unexpected results. Compared with (PDMS), PTFPMS has a higher liquid surface tension, a similar critical surface tension of wetting, and a considerably lower solid surface tension, as determined by water and methylene iodide contact angles and the method of Owens and Wendt (67). These results are summarized in Table X (7, 67, 72-74, 76, 77), in which PTFPMS is compared with two other fluorocarbon polymers, poly(tetrafluoroethylene) (PTFE) and poly(chlorotrifluoroethylene) (PCTFE). PTFE behaves like PTFPMS, whereas PCTFE behaves like PDMS. 

Xu Z, Holland NB, Marchant RE (2001) Conformations of short-chain polyethylene oxide) lipopolymers at the air-water interface a combined film balance and surface tension study. Langmuir 17 377-383... 

From surface tension studies of bola-surfactants, it is concluded that they exhibit wicket-like conformations at the gas-water interface [239,428,430,431], In micelles and liquid crystals however, a stretched conformation is preferred [436,437] this implies that surface tension data and interfacial tension data do no more describe the micellar interface with all the implications for solubilization (compare Sect. 3.4). In fact, some reports stress the extremely low solubilization capacity of bola-surfactants [431,432, 437,438], although others obtain capacities comparable to the ones of the monomers [430]. Also noteworthy, solubilized fluorescence probes indicate a more polar environment for the solubilizates than in micelles of the monomers [430-432], but micellar aggregation numbers of the bola-surfactants are comparable or only slightly lower [429,432, 438, 439]. In exceptional cases, very high aggregation numbers and the existence of an additional pre-CMC are observed [440]. 

Sucrose diffusion studies are reported by several authors (U2, 82, 119) and surface tension studies are now in the literature (12, 120). Sherrill recently gave information on the thermal expansion of crystalline sucrose (99). Thermal conductivity (92) and electrical conductivity (32) of sucrose solution recently have been reported. As research in food science continues it is felt these data may be of... 

The dynamic surface tension studies of Tritons indicate that the surface tension decrease in the short time range is faster (as compared with the usual diffusion models) [60,61]. This fact supports the conclusion about the existence of a reorientation process for Tritons at the surface. Similarly to the CnEOm, in the homologous series of Tritons the b value also increases with the m (cf Fig. 3.38). This again supports the hydrophilic-hydrophobic character of the EO groups. From the temperature dependence of the adsorption equilibrium constant b (cf. Table 3.15), one can estimate the thermodynamic characteristics of Triton X-100 adsorption at the water/air interface. In particular, the AG values can be calculated at various temperatures using Eq. (3.11), and then estimate the standard enthalpy (AH ) and standard entropy of adsorption (AS ) via Eqs. (2.180) and (2.181). 

Nakanishi, H., Wang S.J., and Jean, Y. C., Microscopic surface tension studied by positron annihilation, in Positron Annihilation Studies of Fluids, Sharma, S. C., Ed., World Scientific, Singapore, 1988, p. 292. 

Introduction Anions have a strong tendency to adsorb specifically at metal surfaces, for example, to estabKsh a direct bond with the electrode by partial loss of their hydration shell. As a consequence of the contact with the electrode, the ionic character of the anions is markedly reduced, resulting in a higher surface concentration than in case of nonspecific adsorption. This effect was first observed in double-layer studies on mercury [229, 230] and later confirmed and studied in detail on single-crystal solid electrodes [231-234]. Specifically adsorbed anions can form various types of ordered structures, either more open (cf. sulfate on Au(hld) [235, 236]) or close-packed as reported for halides on different solid electrodes [21]. Cyclic current-potential curves often reveal sharp current peaks, indicative of phase transitions within the anionic adlayers and hence of the existence of ordered phases [21, 237]. Thermodynamic data of specific anion adsorption was obtained in surface tension studies (on mercury only [229,238-240]), capacitance measurements [231-233], cyclic voltammetry, and chronocoulometry [234]. As an... 

In strongly polar solvents, like formamide and ethylene glycol, micelles are formed with qualitatively the same features as in water. As exemplified by surface tension studies in Figure 19.15, the CMC is much higher in formamide than in water, in this case 100 mM compared to 1 mM in water. It is a general feature, also exemplified by smaller micelle radii and aggregation numbers, that self-assembly is much less co-operative in... 

MAH Mahajan, S., Shaheen, A., Banipal, T.S., and Mahajan, R.K., Cloud point and surface tension studies of triblock copolymer-ionic surfactant mixed systems in the presence of amino adds or dipeptides and electrolytes, J. Chem. Eng. Data, 55, 3995,2010. 

Santos, C.S. and Baldelli, S. (2008) Gas-liquid interface of hydrophobic and hydrophilic room-temperature ionic liquids and benzene sum frequency generation and surface tension studies. 

Surface tension studies, yielding results similar to the above, have been obtained on other combinations of polyelectrolyte/oppositely charged surfactant systems. These include poly-L-lysine/SDS (75), carboxymethylcellulose/alkyl TAB surfactants (76), and sulfonated polyacrylamide/DTAB (77,78) combinations. 

Finally, by way of illustration, we mention a polymer type currently receiving much attention. The polymer is referred to as hydrophobically modified ethoxylated urethane (HEUR), the reaction product of a PEG and a diisocyanate, end-capped with a long chain alcohol or amine. HEURs are already recognized as having much potential as associative thickeners in coating formulations. Their structure suggests they will show pronounced interaction with surfactants in solution and this is indeed the case. Here we refer to two recent studies. The first by Hulden (95) included surface tension studies of the polymer... 

Eqs 2.8 constitutes the Gibbs equation that is of uppermost importance in surface chemistry. It can be used to derive surface excess amoimts from experimental surface tension studies. 

Densities, p, of all of the liquid R s, except Tm, have now been measured. Best estimates of these densities from presently available data are shown in table 1, along with d pg)/dT. Estimates of uncertainty are also shown, where possible. In cases in which the data are not reconcilable, more than one value are listed. Measurements of Pg and d(pg)/dr for liquid Sc, Y, and the heavy lanthanides are particularly difficult, and much of the available data is due to the substantial work of Kononenko and his co-workers (Kononenko et al. 1984). Unfortunately, the sessile drop method they have employed, while being a method of choice for their surface tension studies, is subject to uncertainties in pg of about 2% at higher temperatures (Crawley 1974). Moreover, this method may provide values of d(pg)/d7 which are up to 3x too large in magnitude, as can be seen in cases in which data from other methods are also available for comparison. (See Kononenko et al. 1984, Seerveld et al. 1983, and Wittenberg et al. 1963, for example.)... 

The EMA anhydride resins may be treated with iV,7V-dialkylaminoal-cohols to produce polyampholytes, ammonia, and primary or secondary amines to produce amides and a host of other mono and polyfunctional active hydrogen compounds to produce a wide variety of derivatives. The primary amine derivatives, i.e., amide-ammonium salts, may be transformed with heat to imide copolymers.Surface tension studies have been explored on EMA resins and octadecylamine derivatives of the copolymer.The effect of steric hindrance on accessibility, inhomogeneous consideration, electrostatic effects, etc., on the reaction of typical aliphatic amines and polymeric amines (polyethylene imine) with propylene-MA copolymer have been recently examined in great detail.The complexity of the reaction did not allow complete separation of the many variables. 

A dynamic surface tension study of gemini surfactant/conventional surfactant mixtures revealed a diffusion-controlled formation of the mixed surfactant adsorbed layer [127]. 

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