Viscosity associating polymer

The effect of tetrahydrofuran on the polymerization of isoprene in hexane has been studied by Morton and co-workers (73, 74). The viscosity method was used to measure the degree of association. This was found to drop from 2 in pure hexane to about 1.3 with a ratio of THF to polyisoprenyllithium of 100 and dissociation of the polymer aggregates was complete at ratios of 500—700. With the reasonable assumption that the only species present in significant amounts were associated polymer molecules and etherates, it was possible to find the concentration of etherate present under all conditions. An equilibrium constant could be evaluated from the overall process... 

Viscosity of dissolved polymers drops irreversibly under acoustic treatment65 A8). The depolymerization process us rather fast during the first minutes of the treatment and then it becomes slow and ceases completely when the equilibrium molecular mass (MM) M is reached. The higher the polymer s initial molecular mass N0, the higher the rate of destruction. The majority of authors associate polymer destruction in solution with cavitation effects occurring under acoustic treatment. 

The conversion of dextran with 1,2-epoxy-3-phenoxypropane, epoxyoctane or epoxydodecane may be exploited for the preparation of amphiphilic dextran derivatives. Polymeric surfactants prepared by hydrophobic modification of polysaccharides have been widely studied, starting with the pioneering work of Landoll [261]. Neutral water-soluble polymeric surfactants can be obtained by reaction of dextran with 1,2-epoxy-3-phenoxypropane in 1 M aqueous NaOH at ambient temperature (Fig. 35, [229,233]). The number n of hydrophobic groups per 100 Glcp units varies between 7 and 22 depending on the reaction conditions. 2-Hydroxy-3-phenoxy propyl dextran ethers (DexP) behave like classical associative polymers in aqueous solution. In dilute solution, the intrinsic viscosity decreases significantly whereas... 

Both RAMEB and SDS are called rheology modifiers, since they greatly increase and decrease viscosity. Since their discovery, CD-based rheology modifiers have been found for a great variety of associative polymers, such as a-CD for dodecylamido-polyacrylic acid [194], HP- 3-CD for hexadecyl modified hydroxyethyl-cellulose [195], and RAMEB for adamantane modified polyacrylamide [196],... 

In summary, these solution studies of sodium salts of lightly sulfonated polystyrene In tetrahydrofuran verify the presence of associating polymer behavior In lonomer solutions with nonionizing solvents. The results provide a molecular basis for the understanding of solution viscosity behavior. Individual lonomer colls are observed to retain constant dimensions while associating... 

This shear reversibihty is very beneficial in enhanced oil recovery field applications. It improves the well injectivity because of the shear thinning effect at the perforation and near the wellbore. Far away from the wellbore, flow velocity is reduced and viscosity is restored. For the hydrophobically associating polymers, both shear thickening and shear thinning were observed by Bock et al. (1988). It has also been reported that the viscosity after shearing was stopped was higher than that before shearing (McCormick et al., 1988). 

The parameter ji defined in Eq 2.81 is a measure of the polymer-polymer miscibility — negative values indicate immiscibility, positive the miscibility. Three series of blends were examined (1) PVC/PMMA, (2) PiBMA/PMMA, and (3) PiBMA/PVC. In agreement with the calculated values of the parameter the first of these three blends was found miscible, whereas the two other immiscible in the full range of composition. However, the method is, at best, qualitative. For example, the effect of solvent on the parameter was not investigated, but fundamentals of intermolecular interactions make it dubious that non-polar and strongly polar solvents will lead to the same value of the parameter The author observed that the method breaks down for polymer pairs that form molecular associations. Intrinsic viscosity measurements were also used to evaluate intermolecular interactions in blends of cellulose diacetate with polyvinylpyrrolidone [Jinghua et al, 1997]. 

Another issue was the applicability of this approach to characterize the dilute-solution properties of associating polymers. Reduced viscosity is a linear function of the polymer concentration at low concentrations for the systems in this study, so the use of a Huggins-type relationship is justified. 

A further complication to understanding the rheology of hydrophobically associating polymers is their unique response to shear rate and solvent quality (e.g., salt content). As shown in Figures 5 and 6, the viscosity can be independent (Newtonian), decrease (pseudoplastic), or even increase (dilatant)... 

Polymer Characterization. Viscosity. Solution viscosities of the NaAMPS copolymers were determined with a Cannon-Ubbelohde four-bulb shear dilution viscometer (size 100). Solution viscosities of the associative polymers were determined with a Contraves low-shear rotational rheometer at a shear rate of 1.28 s" All viscosity studies were conducted in the absence of surfactant at temperatures in the range of 25-45 °C and [NaCl] ranging from 0 to 0.684 M. 

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