Spectroscopic investigations of polyamido amine starburst dendrimers usingthe solvatochromic probe phenol blue

The physical and chemical properties of PAMAM-AT dendrimers' interior were investigated using the fluorescent, solvatochromic probe phenol blue. In aq ueous solutions of each generation studied except GO, two discrete dye popu lations were clearly observed. PAMAM-AT dendrimers were shown to form a tig ht, nonpolar association with the majority of available dye within the dend rimer interior, probably near its core. In the absorption and steady-state fluorescence emission spectra, a microenvironment of decreasing polarity in increasingly larger-generation PAMAM-AT dendrimers (up to G3) is seen for the associated probe. The remaining larger-generation dendrimers (G4-8) all provide a microenvironment of essentially equal polarity. Fluorescence ani sotropy values for phenol blue in the PAMAM-AT dendrimers demonstrate the d ye's sensitivity to the changing molecular volumes of the dendrimer generat ions. Model compounds that mimic PAMAMAT's surface groups and branching moi eties were used to better define the associated dye's location. The mimics farther confirm that phenol blue is associated inside the dendrimer, where it does not interact with the dendrimer surface groups.