Aggregation Phenomena in Aqueous Solutions of Uncharged Star Polymers with a Porphyrin Core

Uncharged star polymers having a porphyrin core and four poly(ethylene glycol)methyl ether (PEGME) armshave been synthesized and investigated (through the study of the structural and dynamical properties) as afunction of the molecular mass of the arms, in different thermodynamic conditions. Molecules with shortPEGME arms are insoluble in water, whereas in the presence of long PEGME chains, the star polymers arewater-soluble; for the intermediate length of the arms, the building up of large rigid monodisperse aggregates,driven by the diffusion limit aggregation mechanism, has been observed by means of static and dynamiclight scattering. These aggregated systems, whose sizes are modulated by changing the pH and triggered bythe chain flexibility, can be well described in terms of the DLVO interparticle potential in the frame of thecolloidal theory