Determination of molar masses and distributions

Because of its simplicity, a particularly important method for determining molar masses is the measurement of the intrinsic viscosity [ j] for a polymer solution. This quantity is defined as the limit of ( j — s)/( %) as the concentration c of the solution tends to zero, where rj and re the viscosities of the solution and of the pure solvent, respectively. For a mono-disperse polymer the relationship between [ ] and the molar mass 

M is [rj = KM°, where K and a depend on the polymer, the solvent and the temperature. Values of M calculated from this expression for a polydis-perse polymer lie between M and and are usually closer to M . 

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