Determination of viscosity average molecular weight from number and weight average molecular weights

A theoretical equation for the viscosity average molecular weight is derived as (M) over bar (v) = {(1/y(c)) (Gamma>(*) over bar * (z+a+1)/(Gamma>(*) over bar * (z+1)}(1/a)(M-0), where the adjustable parameters, y and z, of the Schultz-Zimm distribution can be determined from the number and weight average molecular weights. When the value of the exponent, a, appearing in the relation between the intrinsic viscosity and the viscosity average molecular weight is in the range from 0.6 to 0.8, as is the case for the most polymers, the viscosity average molecular weight is much more close to the weight average molecular weight than to the number average molecular weight.