Structure of poly(vinyl pyrrolidone) – C70 complexes in aqueous solutions

Aqueous solutions of poly(vinyl pyrrolidone)–fullerene complexes, PVP/C70, have been studied using static and dynamic light scattering. Two diffusive processes were observed. The slow diffusion describes the motion of large PVP/C70 clusters, whereas the fast diffusion is associated with the presence of single PVP molecules or small individual PVP/C70 complexes of the order of a single PVP chain. The molar mass and the size of the PVP/C70 clusters increase upon increasing the fullerene content. However, when the fullerene content is kept constant, an increase in the molar mass of the matrix PVP does not influence the mass and the size of the clusters. Dilution of the PVP/C70 solutions has no effect on the clusters either. In PVP/C70 there is a specific molar ratio of C70 per repeating units of PVP that is same for all the samples studied.