Dependence of the dimension of the associates of water-soluble tris-malonate of light fullerene – C$_{60}$ [= C(COOH)$_2$]$_3$ in water solutions at 25$^{\circ}$C

Investigation of the concentration dependence of the size and type C$_{60}$ [= C(COOH)$_{2}$]$_{3}$ aggregation in aqueous solutions at 25$^{\circ}$C was accomplished with the help of a dynamic light scattering method. It was determined that three types of aggregates are realized in the solutions. The average number of C$_{60}$ [= C(COOH)$_2$]$_3$ molecules in smaller aggregates and all types of aggregates were calculated. One can see that over the whole concentration range, from 0.01 to 10 g/dm$^{3}$, aqueous solutions of C$_{60}$ [= C(COOH)$_2$]$_3$ are characterized by sub-micro-heterogeneous behavior (because second-type aggregates with the linear dimensions - hundreds of nm are formed in all solutions). Additionally, the most concentrated solution (C = 10 g/dm$^{3}$) is characterized by micro-heterogeneous or colloid behavior (because third-type aggregates with the linear dimensions on the order of $\mu$m – are formed). In order to describe or explain such behavior, a stepwise aggregation model was invoked.