Determination of dendrigraft poly-L-lysine diffusion coefficients by Taylor dispersion analysis

This work focuses on the physicochemical characterization of dendrigraft Poly-L-lysines (DGLs) obtained by polymerization of N-carboxyanhydride in buffered water (pH 6.5). Diffusion coefficients (D) and hydrodynamic radii (Rh) of five successive DGL generations were determined by Taylor dispersion analysis (TDA). To our knowledge, this is the first experimental work using TDA for the characterization of dendrimer-like structures. Experimental Rh values obtained by TDA were compared to those derived from dynamic light scattering and size exclusion chromatography coupled to a triple detection (refractive index, viscosimetry, and static light scattering). Significant differences were obtained, especially for the highest generations, as a result of the inherent contribution of aggregates to the light scattering intensity. For that reason, TDA was found to be the most appropriate technique for determining the D values of these hyperbranched macromolecules. Regarding their physicochemical behavior, the experimental results confirm that DGLs are very similar to trifunctional dendrimers (exponential growth of the molar mass, almost linear variation of the hydrodynamic radius, high branching density, and maximum of the intrinsic viscosity or of the free volume fraction for generation 4).