Surface tension polymer solution

In general, the process of electrospinning may be affected by several parameters, among which the main ones are characteristics of polymer viscosity and conductivity of the polymer solution, surface tension, electric field, distance between the capillary and the collector object, the form of the collector and environmental conditions. 

Ruckenstein and Huber [6] worked out a different model by trying to eliminate the shielding parameter and the problems associated with it. They introduced a global interaction parameter, Amicelle surface tension and was claimed to be an experimentally determinable parameter from hydrocarbon-polymer solution surface tension measurements. The use of macroscopic parameters such as the surface tension to describe local molecular interactions between the micelle core and its environment has been criticised recently [7]. Furthermore, the surface tension depends on the polymer concentration therefore, it is not determined unambiguously at which composition the surface tension should be measured. 

Plot the scaling behavior for the surface tension of polystyrene solutions using Eq. III-64, for N = 1,000 and T from zero to Tc- Now plot the behavior for T = 0.87 for N = 100-1000. Comment on the influence of polymers on surface tension. 

The difference between hydrophobicities of the hydroxyethyl (HE) grouping and the hydroxypropyl (HP) unit is evident in the relative aqueous solution surface tensions(7,8) of the two cellulosic polymers in these comparative references the M.S. of the products is not equal. The dramatic influence of the more hydrophobic HP groupings on surface pressures is illustrated in Figure 2. 

For liquids of low viscosity, a useful measurement technique is the tensiometer, schematically represented in Fig. 2.56. Here, the surface tension is related to the force it takes to pull a platinum ring from a solution. Surface tension for selected polymers are listed in Table 2.12 [71 ], for some solvents in Table 2.13 [58] and between polymer-polymer systems in Table 2.14 [71],... 

In the case of a mixture of surfactant and polymer, the surface tension method has become popular and has had a significant impact in this area since 1967, when Jones published his work [14] on mixtures of polyethylene oxide (PEO)/SDS by using the surface tension method. From the plot of surface tension versus -log concentration at a certain concentration of polymer, one can evaluate whether and where the surfactant and polymer associate (some call it clusters) in the bulk solution and at the air/water interface. 

In addition to solution viscosity and conductivity, some nanoparticle fillers also can alter the surface tension of the spinning solutions by forming strong interactions with polymer chains and/or solvent molecules. These nanoparticle fillers can affect the stmcture of electrospun nanofibers by changing the solution surface tension. 

The mechanism of formation of the above instantaneously prepared nanoassemblies and their structure were analyzed by surface tension measurements and H NMR spectroscopy [21]. MD is a typical soluble amphiphilic molecule, which may be adsorbed at the air/water interface. It was observed that the injection of native P-CD in the solution beneath the adsorbed MD monolayer does not change the surface tension, however upon the injection of P-CD polymer the surface tension increases this behavior indicates the desorption of the polymer from the interface, and shows a cooperative effect of P-CDs present in the P-CD polymer on MD desorption. 

A recent design of the maximum bubble pressure instrument for measurement of dynamic surface tension allows resolution in the millisecond time frame [119, 120]. This was accomplished by increasing the system volume relative to that of the bubble and by using electric and acoustic sensors to track the bubble formation frequency. Miller and co-workers also assessed the hydrodynamic effects arising at short bubble formation times with experiments on very viscous liquids [121]. They proposed a correction procedure to improve reliability at short times. This technique is applicable to the study of surfactant and polymer adsorption from solution [101, 120]. 

In polymer solutions and blends, it becomes of interest to understand how the surface tension depends on the molecular weight (or number of repeat units, IV) of the macromolecule and on the polymer-solvent interactions through the interaction parameter, x- In terms of a Hory lattice model, x is given by the polymer and solvent interactions through... 

Smith [113] studied the adsorption of n-pentane on mercury, determining both the surface tension change and the ellipsometric film thickness as a function of the equilibrium pentane pressure. F could then be calculated from the Gibbs equation in the form of Eq. ni-106, and from t. The agreement was excellent. Ellipsometry has also been used to determine the surface compositions of solutions [114,115], as well polymer adsorption at the solution-air interface [116]. 

The extensive use of the Young equation (Eq. X-18) reflects its general acceptance. Curiously, however, the equation has never been verified experimentally since surface tensions of solids are rather difficult to measure. While Fowkes and Sawyer [140] claimed verification for liquids on a fluorocarbon polymer, it is not clear that their assumptions are valid. Nucleation studies indicate that the interfacial tension between a solid and its liquid is appreciable (see Section K-3) and may not be ignored. Indirect experimental tests involve comparing the variation of the contact angle with solute concentration with separate adsorption studies [173]. 

The lubricating properties of tears are an important feature in normal blinking. Kalachandra and Shah measured the coefficient of friction of ophthalmic solutions (artificial tears) on polymer surfaces and found no correlation with viscosity, surface tension or contact angle [58]. The coefficient of friction appears to depend on the structure of the polymer surfaces and decreases with increasing load and sliding speed. 

The circular cross section of the polymer blobs does not prove that the polymer existed in solution as a tangled coil (although this is the case). The shape displayed by the particles in the photograph is probably due in part to surface tension occurring during the drying of the sample. 

The surface of PTFE articles is sHppery and smooth. Liquids with surface tensions below 18 mN/m(=dyn/cm) are spread completely on the PTFE surface hence, solutions of various perfluorocarbon acids in water wet the polymer (78). Treatment with alkafl metals promotes the adhesion between PTFE and other substances (79) but increases the coefficient of friction (80). 

Surface Tension. The surface tension of aqueous solutions of PVA varies with concentration (Fig. 10), temperature, degree of hydrolysis, and acetate distribution on the PVA backbone. Random distribution of acetyl groups in the polymer results in solutions having higher surface tension compared to those of polymers in which blocks of acetyl groups are present (74—77). Surface tension decreases slightly as the molecular weight is reduced (Fig. 11). 

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