Aqueous solutions rheology

Hydrophobically associating water-soluble polymers are of interest because of their unusual properties in solution. Even small levels of hydrophobic groups on water-soluble polymer backbones can have a profound effect on aqueous solution rheology. For example, solutions of such polymers show enhanced viscosification efficiency, shear-thickening rheology, as well as improved shear and salt stability [1-19]. 

Rheology. PVP solubihty in water is limited only by the viscosity of the resulting solution. The heat of solution is — 16.61 kJ/mol (—3.97 kcal/mol) (79) aqueous solutions are slightly acidic (pH 4—5). Figure 2 illustrates the kinematic viscosity of PVP in aqueous solution. The kinematic viscosity of PVP K-30 in various organic solvents is given in Table 13. 

Hvidt, S Jorgensen, EB Brown, W Schillen, K, Micellization and Gelation of Aqueous Solutions of a Triblock Copolymer Studied by Rheological Techniques and Scanning Calorimetry, Journal of Physical Chemistry 98, 12320, 1994. 

Prud homme, RK Wu, G Schneider, DK, Structure and Rheology Studies of Poly(oxyethy-lene-oxypropylene-oxyethylene) Aqueous Solution, Langmuir 12, 4651, 1996. 

Electrolyte Effect on Polymer Solution Rheology. As salt concentration in an aqueous poly(1-amidoethylene) solution increases, the resulting brine becomes a more Theta-solvent for the polymer and the polymer coil compresses(47) This effect is particularly pronounced for partially hydrolyzed poly(l-amidoethylene). The... 

Ochi, A., Nemoto, N., Magoshi, J., Ohyama, E., and Hossain, K. S. (2002b). Rheological behaviors of aqueous solution of silk fibroin./. Soc. Rheol.Jpn 30, 289-294. 

A. Farooq, Rheological Modifiers for Aqueous Solutions, in G. Broze, (ed.), Handbook of Detergents, Marcel Dekker, New York, 1999. 

There is now a solid body of available knowledge to indicate that the general features of biopolymer self-assembly in bulk aqueous solutions can account for various detailed aspects of the stability, rheology and microstructure of oil-in-water emulsions (and foams) stabilized by the same kinds of biopolymers (Dickinson, 1997, 1998 Casanova and Dickinson, 1998 Dickinson et al., 1997, 1998 Semenova et al., 1999, 2006 van der Linden, 2006 Semenova, 2007 Ruis et al., 2007). In particular, the richness of the self-assembly and surface-active properties of the... 

On the strength of all the examples presented in this chapter, the reader should be convinced that variations in self-assembly of food biopolymers in aqueous media can have an enormous influence on food colloid stability, rheology and microstructure. It therefore seems reasonable to infer that further study and understanding of the molecular mechanisms of self-assembly and interactions of biopolymers in aqueous solution should provide increased opportunities for the creation of new classes of structured soft materials with potential application for incorporation in a wide range of new food and pharmaceutical products. 

Both k and k 1 are used extensively in this chapter and Chapters 12 and 13 (as well as in the sections on the rheology of charged dispersions in Chapter 4). Table 11.3 lists numerical values for these quantities and the pertinent equations for their calculation for aqueous solutions at 25 °C. This table may be consulted as a source for k and k 1 values when these are required for exercises in these chapters. 

Effect of addition of homopolymer, salt or conventional surfactants The effect of addition of PEO and PPO homopolymers on the gel formation of Pluronic F127 (defined in Fig. 4.3) in aqueous solution has been studied by Malm-sten and Lindman (1993). The structure, studied via SANS, and rheology of neat F127 solutions in the concentration range 10-20% has been probed by Prud homme et al. (1996). Addition of PEO can reduce the gel region and/or eliminate it at sufficiently high PEO concentration. The amount of PEO required to melt the gel depends on the copolymer concentration and decreases with... 

Fig. 4.16 Phase diagram for aqueous solution of PEO iBio determined using SAXS and rheometry (Pople et al. 1997). The filled symbols mark the phase boundaries determined by SAXS, with the broken line as a guide to the eye, and the solid lines mark transitions determined using rheology (Deng et al. 1995 Pople et al. 1997). The error bars indicate uncertainties associated with the phase transitions determined from repeated heating and cooling ramps.

A surfactant at low concentration in aqueous solution exists as monomers (free or unassociated surfactant molecules). These monomers pack together at the interface, form monolayer and contribute to surface and interfacial tension lowering. Although this phenomenon is highly dynamic (surfactant molecules arrive and leave the interface on a very rapid timescale), molecules at the interface interact with the neighbouring molecules very strongly which enables measurement of the rheological properties of the monolayer. 

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