Light-scattering in solution

When particles are suspended in a liquid, the mixture appears cloudy. This cloudiness is caused by repeated scattering of light by the suspended particles which deflects the incoming light, preventing it from travelling in a straight line. It is a 

To simplify the above equation the following substitutions are usually made  

To obtain M in such cases, it is necessary to extrapolate results to zero concentration and zero angle this is usually done using a so-called Zimin plot (see Cantor and Schimmel for details). 

In addition to the molar mass, this analysis also provides information about the radius of gyration of larger partides, which is a measure of the shape and size of the molecule. This quantity is defined as the weight-average distance of the individual elements of die molecule from the centre of mass  

Analytical expressions can be derived for certain shapes or limiting cases which allow the radii of gyration to be calculated. For a solid rod of length L the radius of gyration is given by the equation 

---

Light scattering in solution Fairly fast wide range of mol. wt. Must measure dn/dc several concentrations necessary for most (but not all) apparatuses requires calibration and rigorous exclusion of dust 5... 

Kay, C. M., and Bailey, K. (1960). Light scattering in solutions of native and guanidinated rabbit tropomyosin. Biochim. Biophys. Acta 40, 149-156. 

P. Debye, Light scattering in solutions, Journal of Applied Physics 15 (1944) 338-342. 

Debye, P. (1944). Light scattering in solutions./. Appl. Phys. 15 338-342. 

Veis, A., and Eggenberger, D. N. (1954). Light scattering in solutions of a linear polyelectrolyte. 

An interesting theoretical treatment of light scattering in solutions of charged macromolecules has recently been given by J. J. Hermans (1950). 

H. Edelhoch, R. LoNTiEand P. R. Morrison Light Scattering in Solutions of Serum Albumin Effects of Charge and Ionic Strength. J. Amer. chem. Soc., 72, 4641—4656 (1950). 

P. R. Morrison, H. Edelhoch and J. T. Edsall Light Scattering in Solutions of Serum Albumin and y-Globulin. Abstracts of Papers, 114th Meeting, American Chemical Society, pp. 25c—26c (1948). 

Edsall, John T., and Walter B. Dandliker, Light scattering in solutions of proteins and other large molecules. Its relation to molecular size and shape and... 

Information about the molecular weight distributions for D light scattering in solution. When D> the number of cross-links is determined from e.g. the sol/gel fraction, swelling or elastic moduli. 

Debye P (1944) Light Scattering in Solutions. J Appl Phys 15 338-342. 

Electron Microscopy. The electron microscope provides a direct method for determining dimensions of colloidal particles (Figure 4.7). With improved equipment, individual particles as small as only 1-2 nm can be discerned, but measuring the diameter of particles smaller than 5 nm is difficult. Alexander and Her (142) first demonstrated that the particle size of colloidal silica measured by the electron microscope correlated well with particle size determined by light scattering in solution, and also with the size calculated from the specific surface area of the dried silica powder. 

M.E. Elder, thesis "Light Scattering in Solution", Case Inst, of Tech., Cleveland, Ohio, 1951. 

As an additional example of how chain dimensions can be influenced by both the solvent and the method employed in their extraction, consider Table 5, where results on unperturbed dimensions of highly syndiotactic ( conventional ) PMMA are collected. SANS results for C o obtained in the melt are consistently higher than those values obtained from light scattering in solution (ca. 9.5 vs. 8.4). A still lower value of ca. 13-1A is derived from intrinsic viscosity measurements in four different theta solvents assuming Oo = 2.5 x 10 mol . ... 

---