Scattering behavior viscosity

When the fluorescence from a DPA-labeled PSS sample was quenched with T1+, deviation from Stem-Volmer behavior was observed [146]. A measure of success was achieved in description of the data, however, through use of the Hindered Access Model [1] (see Equation 2.13). This complex behavior was considered to reflect the fact that quenching can occur via Tl+ ions which are condensed onto the polyelectrolyte in addition to deactivation by those ions which diffuse through solution. The data were also consistent with an extended PSS conformation in the presence of low concentrations of salt, which is in agreement with other fluorescence data [87,145,150] and light scattering and viscosity measurements [136-139]. 

These types of models and measurements provide an invaluable insight into the stractural evolution of gel networks. From measurements of viscosity and light-scattering behavior, sufficient understanding is gained to begin to tailor gel structures for specific applications. 

The binding behavior of methyl orange to several homopolymers and copolymers containing imidazole and imidazolium salts was investigated as a function of polymer structure and counterion. Polymer-counterion interaction was characterized by light scattering, intrinsic viscosity, and turbidimetry. Dye binding was measured by equilibrium dialysis, spectrophotometric titration, and microcalorimetry. 

This study confirms the concept that polyampholytes take an expanded conformation in aqueous salt solutions which is in contrast to typical polyelectrolyte behavior. Viscosity determinations in conjunction with light scattering studies has provided a general confirmation of the polyampholyte effect in the polymers derived from the ion-pair comonomer in aqueous salt solutions. This effect is related to the ion-binding capabilities of the added electrolytes. 

C. E. loan, T. Aberle, and W. Burchard. Light scattering and viscosity behavior of dextran in semidilute solution. Macromolecules, 34 (2001), 326-336. 

Kaye and Chou39 also studied the effect of base stacking on the conformation of PA using osmometry, intrinsic viscosity, and light-scattering. The ideal behavior (under the 0 conditions) of PA existed at neutral pH (= 7.4) and at 26 and 40 °C from the osmotic measurements. 

The various physical methods in use at present involve measurements, respectively, of osmotic pressure, light scattering, sedimentation equilibrium, sedimentation velocity in conjunction with diffusion, or solution viscosity. All except the last mentioned are absolute methods. Each requires extrapolation to infinite dilution for rigorous fulfillment of the requirements of theory. These various physical methods depend basically on evaluation of the thermodynamic properties of the solution (i.e., the change in free energy due to the presence of polymer molecules) or of the kinetic behavior (i.e., frictional coefficient or viscosity increment), or of a combination of the two. Polymer solutions usually exhibit deviations from their limiting infinite dilution behavior at remarkably low concentrations. Hence one is obliged not only to conduct the experiments at low concentrations but also to extrapolate to infinite dilution from measurements made at the lowest experimentally feasible concentrations. 

Figure 3. Critical concentration behavior of actin self-assembly. For the top diagram depicting the macroscopic critical concentration curve, one determines the total amount of polymerized actin by methods that measure the sum of addition and release processes occurring at both ends. Examples of such methods are sedimentation, light scattering, fluorescence assays with pyrene-labeled actin, and viscosity measurements. Forthe bottom curves, the polymerization behavior is typically determined by fluorescence assays conducted under conditions where one of the ends is blocked by the presence of molecules such as gelsolin (a barbed-end capping protein) or spectrin-band 4.1 -actin (a complex prepared from erythrocyte membranes, such that only barbed-end growth occurs). Note further that the barbed end (or (+)-end) has a lower critical concentration than the pointed end (or (-)-end). This differential stabilization requires the occurrence of ATP hydrolysis to supply the free energy that drives subunit addition to the (+)-end at the expense of the subunit loss from the (-)-end.

The solution behavior of poly(amic acids) was until recently, probably the least understood aspect of the soluble polyimide precursor. However, the advent of sophisticated laser light scattering and size exclusion chromatography instrumentation has allowed elucidation of the solution behavior of poly(amic adds). In the early days of polyimide chemistry, when most molecular weight characterization was based on viscosity determinations, a decrease in viscosity was associated with molecular weight degradation [15, 28, 29]. Upon combination of the two monomers an increase in the viscosity to the stoichiometric equivalence point is observed, followed by a decrease in the solution viscosity as a... 

Thus, Worsfold 133) measured the association behavior, via light scattering, UV-visible spectroscopy and viscosity, of polystyrene chaips capped at one end with the dimethylamine group where the associating group was the bis-(2,6-dinitrohydro-quinol). This bidentate species ... 

Tn the critical region of mixtures of two or more components some physical properties such as light scattering, ultrasonic absorption, heat capacity, and viscosity show anomalous behavior. At the critical concentration of a binary system the sound absorption (13, 26), dissymmetry ratio of scattered light (2, 4-7, II, 12, 23), temperature coefficient of the viscosity (8,14,15,18), and the heat capacity (15) show a maximum at the critical temperature, whereas the diffusion coefficient (27, 28) tends to a minimum. Starting from the fluctuation theory and the basic considerations of Omstein and Zemike (25), Debye (3) made the assumption that near the critical point, the work which is necessary to establish a composition fluctuation depends not only on the average square of the amplitude but also on the average square of the local... 

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