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Small-angle neutron scattering (SANS) experiments on solutions of polystyrene (PSH) and its deuterated homologue (PSD) in deuterated toluene have been performed over a wide range of concentration.Several redundant measurements demonstrated that the high-concentration technique of extracting single-chain scattering functions is highly reliable. Radii of gyration and screening lengths were fitted to power laws and were found to be R N c-".lW and f N c-".'O. The resulta differ significantly from predictions by scaling theory, though the dependence of E on c is in good accord with that previously found by other researchers. These experiments were also analyzed by using recent theoretical results of Muthukumar and Edwards. Measurements at different concentrations yielded a reasonably consistent value of the excluded volume interaction parameter.

This paper relates the symmetric and asymmetric correlation-time distributions found in various relaxation experiments to one another, and to the single correlation time. The reorientation probabilities of the individual molecules are taken as functions of an environmental parameter, loosely termed the ``free volume,'' which is presumed to fluctuate with time. This treatment leads to a symmetric correlation-time distribution when the rate of ``free-volume'' fluctuation is much less than the various rates of molecular reorientation; an asymmetric distribution when these rates are comparable; and a single correlation time when the rate of fluctuation is much larger than the rates of reorientation.

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Proton magnetic relaxation times have been measured in solutions of polyethylene oxide. Molecular weight, temperature, and solution concentration have been systematically varied. Several low-molecularweight oligomers have been studied as well as polymers which vary in molecular weight from 4X1Q3 to 4XIQ6. The results show that in dilute solution both TI and T. are independent of mdecular weight. TI decreases with increasing concentration for concentrations greater than 0.2 g per ml of polymer, but is independent of concentration for more dilute solutions. T. is independent of concentration in the limit of low concentration, but decreases rapidly with increasing concentration. The concentration dependence of T. is a sensitive function of molecular weight. The relaxation mechanism has been analyzed using a model of rotameric transitions and the molecular geometry calculated from the known crystal structure of tbe polymer. The most important term is that arising from a conformational change about the C-C bond, in which the oxygen atoms move from a gauche to a gauche' position. The relaxation times (TIl of water in aqueous polyethylene oxide solutions decrease with increasing polymer concentration, and are independent of the molecular weight of the polymer.