Effect of the ultracentrifuge centrifugal force on the molecular characteristics of poly(vinylcaprolactam) complexes with fullerene C_60

The dilute solutions of poly(vinylcaprolactam) and its fullerene C60 complex have been studied by high-velocity sedimentation, translational diffusion, viscometry, and static and dynamic light scattering. The experiments have been performed for the sample with M ≈ 2.7 × 105. In the absence of external action, supramolecular structures (clusters) whose size and molar mass are much higher than the corresponding characteristics of the polymer matrix appear in solutions of the poly(vinylcaprolactam)-C60 complex. When subject to a strong centrifugal force or an intense shear flow, the supramolecular structures are destroyed and the molecular characteristics of the complex correspond to those of poly(vinylcaprolactam) macromolecules. The dynamics of destruction of the cluster organization in aqueous solutions of fullerene-polymer complexes has been investigated by high-velocity sedimentation. As the angular speed of ultracentrifuge rotor rotation is decreased from 55000 to 10000 rpm, the sedimentation constant S 0 of the poly(vinylcaprolactam)-C60 complex increases by a factor of ∼4. This behavior reflects changes in the size and molar mass of clusters with the centrifugal force acting upon complex macromolecules.

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