Different light scattering

If the absolute diameter or radius of a polymer coil is known, a direct calculation of a critical concentration is possible without viscosimetric data. Common methods for the determination of absolute coil dimensions are the different light scattering methods. The critical concentration calculated from these dimensions is therefore often denoted as the critical concentration of light scattering, c ls> since the radius R (see Chap. 8) can be determined directly from static light scattering. 

Optical properties can also be affected by the fact that filler particles can affect the morphology of the plastic by nucleating its crystallisation at the interface. Thus a composite with different light scattering properties may be obtained. 

Figure 5 shows tluee patterns of light scattered from tlrree different wires. Three graphics of (7) of increasing T/a are shown in figure 6. 

Figure i Light scattered from three different wires. 

Strauss and Williamst have studied coil dimensions of derivatives of poly(4-vinylpyridine) by light-scattering and viscosity measurements. The derivatives studied were poly(pyridinium) ions quaternized y% with n-dodecyl groups and (1 - y)% with ethyl groups. Experimental coil dimensions extrapolated to 0 conditions and expressed relative to the length of a freely rotating repeat unit are presented here for the molecules in two different environments ... 

It is awkward to use two different angles to describe the intensity of light scattered along a particular line of sight, but this situation is easily remedied by referring back to Fig. 10.5. It is apparent from Fig. 10.5 that r cos 0 is the projection of r along either the x, y, or z axis, depending on the choice of 0. We therefore see that... 

As a result of these considerations, the primary difference between a spectrophotometer and a light-scattering photometer is the fact that the photodetector is mounted on an arm which pivots at the sample so that intensity measurements can be made at various angles. 

We must describe the light scattered with interference in terms of phase differences that develop as the waves pass through a molecule consisting of multiple scattering sites. 

This expression formalizes the anticipated conclusion that it is the difference in phase between light scattered by different segments that is responsible for the interference effect we seek to analyze. Equation (10.72) completes the first of the three stages in the development of P(0). 

Even when we discuss the electric field of light without reference to any particular charge, we must be aware of these differences. When that field interacts with a charge, as in light scattering, we will be in trouble unless a self-consistent set of units has been employed. 

Benoit et al.f prepared a mixture of two different fractions of cellulose nitrate and determined the molecular weight of the mixture by light scattering. The mixture was 25.8% by weight fraction A and 74.2% fraction B, where the individual fractions have the following properties ... 

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