Determination of latex particle size by light scattering. VII. The dissymmetry method

Dissymmetry of light scattering at 45 to 135[ddot] has been used to determine the particle size of both mono- and polydisperse latices. For the monodisperse latices the particle diameters found are independent of the wavelength used, and in good agreement with results obtained by electron microscopy and transmission measurements. However, because of the nature of the Mie plots and experimental difficulties, the method is limited primarily to diameters less than 0.60λm. On the other hand, the diameters obtained for polydisperse latices increase with increase in Am to values considerably above the weight-average diameters of the systems. It is shown that this variation of D is a function of the particle-size distribution of the latices as well as the wavelength, and that it is not possible to define for such latices conditions of measurement which will correspond to a definable type of average for the diameters obtained.