Surface tension of polymer solutions

Mean-field theories of the surface tension of polymer solutions have been developed using the Cahn square gradient approach for interfacial properties of solutions and mixtures both for attractive and for repulsive air/liquid interfaces (Cahn and Hilliard 1958), in a way analogous to the treatment of surface segregation in polymer blends given in section 5.1. For situations in which a surface excess was formed, the volume fraction profile was a hyperbolic cotangent, whereas repulsive profiles were described by hyperbolic tangent functions. Values of the surface tension of semi-dilute solutions of polyst)n ene in toluene (a depletion layer) and polydimethyl siloxane in toluene (an attractive interface, a surface excess formed) were well described by this theory. 

Surface tension of polymer solution containing pyridine (12.5% PCL solution). ... 

G. B. Tanny, The Surface Tension of Polymer Solutions and Asyrmnettic Membrane Formation,... 

The surface tension of polymer solutions can be conveniently measured using the simple Du Nouy ring technique (Geng et al. 2005), where a wire loop of known circumference is dipped in the solution and the maximum force needed to slowly raise it out of the solution is measured. The WiUielmy plate method (Seoul et al. 2003) essentially substitutes a platinum plate for the ring. With small samples of solution available for the measurement, however, a platinum rod might be substituted for the plate. In practice it is important to minimize the evaporation of solvent during the measurement. 

KU Okubo, M. and Ueberreiter, K., Surface tension of polymer solutions 7. Colloid Polym. ScL, 256, 941, 1978. 

Ober R, Paz L, Taupin C et al. Study of surface tension of polymer solutions Theory and experiments. I. Good solvent conditions. Macromolecules. 1983 16 50-55. 

Figure 2. Effect of EtOH/water composition on surface tension of EtOH/water solution and on incremental surface tension of polymer solutions o EtOH/water + 0.2% HMHEC, A 0.4% HEC.

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. 

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). 

The measurement of the surface tension of SDS solutions at constant polymer additions was performed to investigate any possible interactions between SDS and the polymers used in these experiments. The results, shown in Figure 2, indicate no interaction between SDS and either PAA or PAM. Interactions between similarly charged surfactant and polyelectrolyte are not common as electrical effects frequently dominate to prevent any hydro-phobic or hydrogen bonding interaction. The hydrophilic nature of the amide dipole of polyacrylamides has been suggested (11) as a possible factor in preventing interaction with sodium dodecylsulfate,... 

Kollicoat IR is a unique polymer for pharmaceutical applications prepared by a graft polymerization process of polyethylene glycol (25%) with polyvinyl alcohol (75%). Kollicoat IR dissolves quickly in water and aqueous solutions of acid and alkali and reduces the surface tension of aqueous solutions to allow the solutions to have high spray rates. The polymer film is very flexible, not tacky, and easily colored. The polymer can be used as instant release coating, pore former, binder, protective colloid, etc. 

The lattice fluid equation-of-state theory for polymers, polymer solutions, and polymer mixtures is a useful tool which can provide information on equa-tion-of-state properties, and also allows prediction of surface tension of polymers, phase stability of polymer blends, etc. [17-20]. The theory uses empty lattice sites to account for free volume, and therefore one may treat volume changes upon mixing, which are not possible in the Flory-Huggins theory. As a result, lower critical solution temperature (LCST) behaviors can, in principle, be described in polymer systems which interact chiefly through dispersion forces [17]. The equation-of-state theory involves characteristic parameters, p, v, and T, which have to be determined from experimental data. The least-squares fitting of density data as a function of temperature and pressure yields a set of parameters which best represent the data over the temperature and pressure ranges considered [21]. The method,however,requires tedious experiments to deter-... 

Fig. 43. Concentration dependence of the surface tension of aqueous solutions of polymerized methacrylic surfactant 79 as function of the amount of initiator used. (Adapted with kind permission from [229]). Top to bottom polymer (0.5 mol % AIBN used), polymer (1 mol % AIBN used), polymer (5 mol % AIBN used), monomer...

The surface tension of mixed solutions of polymers and surfactants of the same charge is slightly smaller than the surface tension of the polymer-free surfactant solution. In this case again, there is no binding of the surfactant to the polymer, but an ionic polymer shifts the critical micellar concentration (CMC) of the solutions to lower values, exactly as a common salt.13... 

Figure 3 Dynamic surface tensions of MeC solutions for different polymer concentrations...

Solution properties are those such as molecular weight, molecular weight distribution, and architecture of the polymer, and properties such as viscosity, conductivity, dielectric constant, and surface tension. The polymer solution must have a concentration high... 

PVT data for polymers are important both from the academic and practical points of view. On the scientific side, PVT data are frequently needed for model considerations on polymer solutions and melts. On the industrial side, these data are needed for process design. An equally important thermodynamic quantity is the surface tension of polymer melts, due to their relevance in wetting, adsorption, and adhesion. It may strongly govern such surface processes as film formation or coating. Here we report on PVT data and surface tensions of different random copolymers. We also relate thermodynamic quantities describing bulk properties to surface tension of polymer melts. 

Table 1.3 shows, for example, the surface tension of the solutions of some water-soluble polymers at 25°C (0.1% aqueous solutions of the polymers). Hydroxypropylcellulose (HPC) is a good example of a surface-active polymer. Water solutions greatly reduced surface and interfacial tensions. HPC functions as an assistant in both emulsifying and whipping. HPC combines organic solvent solubility, thermoplasticity and surface activity with the aqueous thickening and stabilizing properties of other water soluble cellulose pol miers. 

Figure 6. Surface tension of (a) solutions containing 1000 ppm polyethylene oxide and SDS on SDBS micelles and (b) solutions containing SDS on SDBS micelles but in the absence of any polymer.

Electrostatic force is the primary driving force in the electrospinning process. The jet emerges from the polymer solution as soon as the surface tension of the solution is overcome by this force. Therefore, the applied... 

Analogous to HME, electrospinning is also a widely used technique in the polymer industry. A schematic of electrospinning process is shown in Fig. 3.11. A polymer solution is drawn through a capillary tube that is subjected to an electric field. As the electric field increases, the feed solution forms a Taylor cone at the tip of the capillary. Once the electric field overcomes the surface tension of the solution, the polymer solution is ejected as an electrically charged jet. Due to the increase in surface area, the solvent evaporates leaving thin filaments of material (50 nm to 5 microns). These fibers are then collected on collector screens for further processing. This technique has been applied for pharmaceutical systems by several researchers... 

---