(164f) Reorientational Dynamics of Pegylated Dendrimers

Dendrimers are an exciting and promising novel class of macromolecular architecture due to their well defined, highly branched, compartmentalized structure in the nanometer size range. The globular morphology of these polymers enables them to encapsulate important molecules such as therapeutic drugs within the interstitial space of their branches for subsequent targeted delivery. Attaching biocompatible PEG on the dendrimer surface increase their water solubility, drug loading capacity and the rate of drug release. To understand and assess these capabilities and to usher the way for the optimization of highly specific tasks in complex environments, such as in vivo targeting applications, it is essential that we acquire a comprehensive knowledge of the dynamics of PEGylated dendrimers on the molecular level.

In this work, an investigation was carried out on the dynamics of systems composed of generation 3 of poly(amidoamine) - PAMAM dendrimers in blends with poly(ethelene glycol) ? PEG with molecular weight of 2000g/mol, as well as the dynamics of dendrimers with linear PEG chains covalently attached to the surface groups. The results were generated over a broad range of temperature and frequency by Dielectric Relaxation Spectroscopy (DRS) and Dynamic Mechanical Spectroscopy (DMS). The principal objective is to elucidate how dynamics vary as a function of temperature, concentration of dendrimers in blends and the number of covalently attached PEG chains in the PEGylated dendrimers.

The initial DRS results of PEG-dendrimer blends reveal a shift of the β process in dendrimers, assigned to the local fluctuations of branch ends that include amino groups, to the lower frequency with increasing concentration of PEG. In PEGylated dendrimers, no effect of concentration on the average relaxation times was observed, but the dielectric relaxation strength was found to increase with increasing number of covalently attached PEG molecules. A complete quantitative picture of the dynamics of PEG-dendrimer blends and PEGylated dendrimers will be presented.