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The hydrodynamic behavior of a number of diene polymers and copolymers (including cis-1,4-polybutadiene, cis-1,4-polyisoprene, butadiene–styrene, and butadiene–acrylonitrile copolymers) has been investigated in suitable mixed τ solvents. The relations of the basic hydrodynamic parameters, namely, the sedimentation constant, the diffusion coefficient, and the intrinsic viscosity, to molecular weight have been established, and may be used in calculating molecular weight distributions of the polymers investigated. For all polymer–solvent τ systems investigated the values of the parameter ϕ⅓P−1 are shown to be considerably lower than those predicted by theory. For all systems mentioned a distinct dependence of sedimentation and diffusion constants on concentration has been established. The experimentally observed regularities are interpreted on the assumption that the hydrodynamic interaction between macromolecules in sedimentation and diffusion processes affects the magnitude of the translational friction coefficient of the macromolecules. The effect of this dependence of sedimentation and diffusion constants on concentration is shown to decrease as the compactness of the macromolecular coils is increased, i.e., when the “specific dimensions” of the macromolecules , in a given solvent are decreased. |
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