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The reduction in molecular dimensions due to the presence of short side chains in otherwise linear polyolefins can very simply by calculated by assuming that the configuration of the main chain is not influenced by the side chains. This enables us to express the intrinsic viscosity–molar mass relationship as a function of the mass fraction of side chains (S): [η] = (1 − S)α+1KPEMνα and, with use of the universal calibration principle, to convert the GPC calibration for purely linear polymers samples into the calibration for short-chain branched polymers: M* = (1 − S)M. Experimental data from literature on short-chain branched poly-ethylenes, and our own data on ethylene–propylene copolymers are used to verify the above assumption. It appears that the experimentally found relations between [η], Mw and M*w (GPC) within the usual accuracy justify this approach.

It is demonstrated that, although addition of n-propanol to aqueous poly(vinyl alcohol) solutions prevents their aging, the polymer is not present in a molecularly dispersed form. Further, it is shown that viscometry is not a suitable method to study the degree of dispersion of poly(vinyl alcohol) in water or water/n-propanol solution. The results of turbidity measurements as a function of poly(vinyl alcohol) concentration, n-propanol concentration and time suggest that it is a change of solvent quality rather than a specific interaction between polymer and n-propanol that is responsible for the suppression of aging effects.

For determination of mol. wt. distribution from sedimentation-diffusion equilibria, the concentrations or the concentration gradients are measured in a number of places in the solution column for equilibria at various rotor speeds. The mol. wt. distribution is represented by a given series of mol. wts. Using a method of linear programming, a digital computer is made to find the weight fractions of the mol. wts. in the sample which fit best with the experimental data. A method of quadratic programming (least squares method) can be used just as well. From a three-peak polystyrene sample (a mixture of three polystyrene samples with narrow distribution), the mol. wt. distribution has been determined in this way. The mol. wt. distribution of the same sample has also been determined by sedimentation velocity analysis at the temperature where the sedimentation coefficient is independent of the concentration. The distributions obtained by these two methods agree well with each other and with the distribution obtained by gel permeation chromatography. The average mol. wts. M a , M w , M z and M z + 1 calculated from these distributions also agree well with the values calculated from the average mol. wts. of the three original samples.

From the intensities of light scattered from dilute and concentrated solutions of a given polymer, the chemical potential of the polymer and the solvent can be determined. Experiments have been carried out with solutions of monodisperse polystyrenes of different molecular weights in a poor solvent (cyclohexane) and in a good solvent (toluene) at different temperatures and at concentrations up to 30 per cent by weight. For all concentrations, the interaction parameter χ appears to be slightly dependent on the molecular weight. The results are compared with those determined by equilibrium ultracentrifugation and critical miscibility measurements.