In recent years, we have made a series of experimental studies of effects of chain stiffness and local chain conformation on the first cumulant Ω(k) of the dynamic structure factor as a function of the magnitude k of the scattering vector for both flexible and semiflexible polymers in the unperturbed ? state. It has then been concluded that the universality predicted by the Gaussian chain theory for the plot of η0 Ω(k)/kBTk~3 against ?S~2?~(1/2)k cannot be realized for flexible polymers even with very high molecular weights (=10~6-10~7), and that the height of the plateau in the k~ 3-region depends on chain stiffness and local chain conformation, as predicted by the helical wormlike (HW) chain theory, where η0 is the solvent viscosity, k_B the Boltzmann constant, T the absolute temperature, and ?S~2? the mean-square radius of gyration. In this study, we further proceed to make an experimental study of the excluded-volume effects on Ω(k)~2.
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