EXPERIMENTAL-EVIDENCE FOR SELF-SIMILAR STRUCTURES IN THE AGGREGATION OF PORPHYRINS IN AQUEOUS-SOLUTIONS

We have studied the aggregation of the porphyrin t-H2Pagg in aqueous s olution by light scattering. The intensity profile of the elastically scattered light, studied in the exchanged wave-vector range 0.2 less t han or equal to q less than or equal to 31.4 mu m(-1), indicates that the aggregation produces large monodisperse clusters having a fractal structure, and is driven by diffusion-limited aggregation kinetics. Ad ditional measurements performed at different q values confirm such a p icture giving a hydrodynamic radius R(H) consistent with the radius of gyration R(g) measured by elastic scattering. This is explained takin g into account the q(2) dependence observed in the mean decay rate of the intensity-intensity correlation function and the effect on this la tter dynamical quantity of anisotropies in the cluster structure.