Viscosity—Molecular Weight Dependence for Short Chain Polystyrenes

Data on the viscosity coefficient η in the limit of zero shear on binary polystyrene mixtures having identical number average chain length Zn (hence identical density) but different weight average Zw establishes that η∼Zw, when Zw<630 chain atoms, confirming the theory of Bueche for the viscosity of short polymer chains. Strong support for Bueche's theoretical equation, η=16N0[(〈s02〉Av/M)(1/v)]Zζ,is provided by the successful quantitative prediction of the observed value of η from the independently measured values of the unperturbed reduced mean-square radius of gyration of the polymer coil 〈s02〉Av/M, of the specific volume v, the friction coefficient per chain atom ζ, and Avogadro's number, N0. Application of this equation now permits ready evaluation of ζ from viscosity measurements on short chain polymers.