Molecular Properties and Aggregation of Porphyrin-modified Polysiloxane in Solutions

Molecular properties and aggregation behavior of a polysiloxane with grafted side chain groups consisting of asymmetrical hydroxy-functionalized porphyrin were studied in dilute solutions. In order to understand the mechanism of aggregation of the polymeric porphyrin derivatives, several analyses of chloroform solutions were performed permitting comparison of the data obtained by means of different techniques. Molar mass and hydrodynamic size of the macromolecules were obtained using the methods of analytical ultracentrifugation, isothermal translational diffusion, and viscometry. Long distance interactions between macromolecules in dilute solutions were detected with static light scattering. With increasing the concentration of the solutions, the electronic and fluorescence spectra bands assigned to generation of H and J aggregates became apparent. The organization of aggregates, which seemed to be favored by chloroform, was visualized by atomic force microscopy images that displayed sponge-like morphology, small triangular particles, characteristic of H aggregates, and nano or micro-structured ring geometries obtained by the side-by-side J-process, coexisting together.