Light scattering of polyphosphates of high molecular weight

This paper reports light scattering and viscosity data concerning a fraction of lithium polyphosphate of high molecular weight (1.0 × 10 6 ) dissolved in LiCl solutions whose concentration varied from 0.025 to 0.4 M . The lithium polyphosphate was obtained by adding a cation exchanger (Dowex 50, lithium form) to an aqueous suspension of insoluble potassium Kurrol's salt. The higher fraction of the dissolved product was then precipitated by adding an alcoholic solution of LiCl. The root mean square end‐to‐end distance of the polyelectrolyte molecule, ( r 2 ), as obtained from the angular dependence of the scattered light, is as much greater as the ionic strength lowers. The Fox‐Flory relation can be applied in the above range of ionic strength. The second virial coefficient becomes zero at a ionic strength of about 0.4, and the ratio ( r / M ) 1/2 = 1.24 × 10 −8 cm. shows that the molecule has a low flexibility. The dependence of the expansion coefficients and of the second virial coefficients on ionic strength is discussed, use being made of the theories concerning polyelectrolyte behavior.