LIGHT-SCATTERING AND FLUORESCENCE PHOTOBLEACHING RECOVERY STUDY OF POLY(AMIDOAMINE) CASCADE POLYMERS IN AQUEOUS-SOLUTION

Diffusion coefficients of polyamidoamine cascade polymers (PAMAMs) wer e measured in aqueous solutions by dynamic light scattering and, after labeling with fluorescein isothiocyanate, by fluorescence photobleach ing recovery. The dynamic light scattering results depended weakly on pH at a high salt concentration, but varied strongly with the concentr ation of added salt in the low-salt limit. The fluorescence photobleac hing recovery values were almost independent of salt concentration. Th e difference between the two techniques is that thermodynamic nonideal ity strongly affects light scattering at the concentrations that are e xperimentally accessible. The hydrodynamic sizes from fluorescence pho tobleaching recovery were somewhat smaller than those from dynamic lig ht scattering in the high-salt limit, despite attachment of the dye. N evertheless, fluorescently tagged PAMAMs should make suitable markers and diffusion probes. (C) 1996 John Wiley & Sons, Inc.