Polymer solutions. VIII. A new absolute method of molecular weight determination of polymers from solution viscosities

An empirical method for absolute molecular weight determination of polymers from viscosity measurements is described. The essential assumptions of the method are: (a) the Huggins' slope constant for any flexible polymer has a maximum value of 0.5 at the precipitation point; (b) the viscosity—concentration plots for a particular polymer in different solvents (when extrapolated) meet at a common point; (c) the ordinate at the common point of intersection [η]R (when the viscosity function is In ηr/c is identical with the limiting viscosity number for the polymer at the point of incipient precipitation); (d) the value of the ordinate at the common point of intersection [η]R is related to molecular weight by the relation [η]R = 9.0 × 10−4M0.5. The method gives satisfactory results in case of polymers like polystyrene and polymethyl acrylate.