Behavior of Dendritic Polymers in Solutions: DLS and NMR Study

Dendritic polymers possess unique properties. High degree of branching, globular architecture and a large number of surface functional group make them promising candidates for functional supramolecular materials. Dendritic polymers have a variety of prospective applications, e.g. functional coatings, adhesives, chemical sensors, photosensitive materials, nanocarriers in drug delivery, gene transfection, tumor therapy, biomimetic systems and the development of vaccines.

Our study were focused on experimental investigations of diffusion of a poly(propylene imine) dendrimer and a hyperbranched polyester in solutions.

A combination of field gradient NMR and DLS was used to study behavior of a poly(propylene imine) dendrimer of 5^th generation (with amine end groups) in methanol-d4 solutions. The self-diffusion coefficient and the collective diffusion coefficient were determined as a function of concentration and temperature. The combination of both techniques permitted accurate estimations of the diffusion coefficient and the hydrodynamic radius at zero concentration, and from the concentration dependences the second virial coefficient.

Diffusion coefficients of dendritic polymers with end groups substituted with alkyl chains were also determined as a function of temperature and concentration. From the diffusion coefficient in zero concentration limit the hydrodynamic radii of the polymer molecules in solutions have been estimated. It was shown that at higher concentrations dendritic macromolecules with modified end groups form aggregates.