Scattering by a Polymer Solution

The intensity /(g) scattered by a polymer solution can always be written in the form... 

The measurement of the intensity I(q) scattered by a polymer solution, gives us almost directly the structure function... 

The intensity of the light scattered by a polymer solution, above that scattered by the pure solvent, is related to the molecular weight of the polymer by (9)... 

Figure 2.30. Schematic of the geometry around a sample ceU in a light-scattering measurement system. A photodetector detects the light scattered by a polymer solution in the beam path into a direction at angle 6 from the forward direction. The vat is filled with an indexmatching liquid.

Autocorrelation of Scattered Field We assume that the scattering volume contains p identical small particles and consider the autocorrelation function of Es(f) for the scattering by the volume. Examples include a suspension of colloidal particles. The autocorrelation of the scattering by a polymer solution will be discussed in Section 3.2.6. 

Because of the fundamental nature of the size of polymer coils, considerable effort has been devoted to the experimental measurement of the size of regular star polymers both in good solvents and under 6-conditions. The size of a polymer coil is obtained from the angular dependence of scattered radiation at low angles. The angular dependence of the intensity of light (or neutrons) scattered by a polymer solution is analyzed in terms of the product of the form factor, P Q), and the structure factor, S Q) ... 

The amount of excess light scattered by dilute polymer solutions compared with that scattered by the pure solvent is used routinely to determine the weight average molecular weight of polymers, A/, ... 

Ahlrichs P, Diinweg B (1999) Simulation of a single polymer chain in solution by combining lattice Boltzman and molecular dynamics. J Chem Phys lll(17) 8225-8239 Akcasu Z, Gurol H (1976) Quasielastic scattering by dilute polymer solutions. J Polym Sci Polym Phys Ed 46(1) 1-10... 

As has been discussed by the present author (18) a similar difficult situation arises in cormection with light scattering from a polymer solution. In this case, one can use q (r) or w (r) equally at least in principle. However, in practice one must use some mathematical assumptions and approximations in deriving these distribution functions and one obtains different scattering formulas. 

Light scattering Ultracentrifugation Measurement of the intensity of light scattered by dilute polymer solution. The intensity is measured as a function of concentration and angle of observation Ww Hundreds to tens of millions... 

In equation (11), 6 is the scattering angle, and X is the radiation wavelength in the polymer solution. The scattered light spectrum produced by a polymer solution depends upon the mass, polarizability and number of polymer coils in the solution, and the magnitude of the scattering field vector. 

A. Akcasu and H. Gurol. Quasi-elastic scattering by dilute polymer-solutions. J. Polymer Sci. Polymer Phys. Ed., 14 (1976), 1-10. 

Anionic polymer(s) and photosensitizer(s) dissolved in a water - alcohol mixture were used as the medium. A standard solution was diluted by 2000 times to reduce light scattering by the polymer particles and to reduce the current density in the working range. 

Kaddur, L.O., Strazielle, C. (1986). Experimental investigation of light scattering by a solution of two polymers. Polymer, 28, 459 168. 

The scattered light intensity from a polymer solution arises from the fluctuations in both the solvent density and the polymer concentration. These fluctuations are considered as stable during the timescale of the measurement in the static mode of light scattering (for more details, see Evans (1972)). The light scattered from just the polymer (in excess of the light scattered from the pure solvent) is given by (Burchard, 1994)... 

Recent theoretical developments have related the turbidity of polymer solutions to the size and shape of the dissolved molecules. The light scattered by a solution in excess of that scattered by pure solvent (r) can be shown12 to be related to the molecular weight by the continued series equation... 

This approach involves two parameters (v and nT) to describe chain swelling and is characterized by an unphysical break of chain statistics at i — j = nT. Due to the awkwardness of the numerical generation of the structure factor when v = 1/2, a simple Debye function with swollen radius of gyration is often used (in an adhoc fashion) to fit scattering data from polymer solutions. 

When light passes through an inhomogeneous medium such as a polymer solution, it is scattered in all directions. The light scattering at an angle 6 by the solute is measured by the excess Rayleigh ratio Re which is defined by... 

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