Diffusion of dendritic polymers through concentrated polymer solutions

Diffusion dynamics of polymers can be very sensitive to polymer architecture. Polymers with novel (or time-varying) architectures could facilitate the release of therapeutic compounds from gels or concentrated polymer solutions with unusual or novel kinetic profiles. Towards this end, we are studying the behavior of model dendritic polymers, the poly(amidoamine)(PAMAM) dendrimers, in aqueous solutions and in concentrated solutions of a "matrix" polymer, poly(ethylene oxide)(PEO). Fluorescence measurements of the environmental polarity of the dendrimers provide evidence for pH-induced confomational changes in mid-sized (generation 6), but not in small (generation 2) dendrimers. In aqueous solution, dendrimer diffusion measurements reveal the fractal-like growth of these molecules, but measurements in aqueous PEO solutions failed to detect any pH dependence of the diffusion coefficient. Specific chemical interactions between the PEO and the PAMAM molecules may dominate their dynamic behavior.