A novel parameter of polymer structure

A need exists for a simple and reliable heterogeneity index to determine the presence of high molecular weight components which may be branched in complex polymers and copolymers. On the basis of theoretical considerations, a proposal is made to employ the ratio of concentrated solution to intrinsic or Mooney viscosity as a heterogeneity index. The basis for the index is that the concentrated solution or melt viscosity is a function of a higher moment of the molecular weight distribution than either the intrinsic or Mooney viscosity. Experimental evidence in the form of light‐scattering measurements and osmometry support the validity of the index when the range of intrinsic viscosities is narrow and other assumptions cited are justified. It is further shown that the heterogeneity index correlates well with the processibility of cis‐polybutadiene.