Determination of constants in the intrinsic viscosity–molecular weight equation

Abstract

AbstractIn the modified Staudinger equation, [η] = Km[Mv]α, the constants Km and α are usually found from measurements of [η] and Mv. As the latter cannot be determined directly, the method adopted in the past has been to prepare fractions, determine Mn or Mw by such absolute methods as osmometry and light scattering, and then to assume that the fractions are sufficiently monodisperse to justify writing Mv = Mn = Mw. An alternative approach has been suggested in this paper, making use of the fact that, for a distribution arising from random degradation, Mv = constant × Mn; it has been shown that the appropriate distribution results from the heterogeneous hydrolysis of cotton. The method has been applied to the case of cellulose triacetate in chloroform and the following results have been obtained: Km = 2.51 × 10−4; α = 1.02.