Self-Diffusion of Hydrophilic Poly(propyleneimine) Dendrimers in Poly(vinyl alcohol) Solutions and Gels by Pulsed Field Gradient NMR Spectroscopy

Abstract

Pulsed-field gradient NMR spectroscopy was used to study the diffusion of three different poly(propyleneimine) dendrimers with hydrophilic triethylenoxy methyl ether terminal groups (generations 2, 4, and 5) in poly(vinyl alcohol) aqueous solutions and gels. The effects of the diffusant size, polymer concentration (from 0 to 0.26 g/mL), and temperature on the self-diffusion coefficients have been studied, and the model of Petit et al. [Macromolecules 1996, 29, 6031] was used to fit the experimental data. The Stokes−Einstein hard-sphere radii were also calculated in the zero concentration limit and were compared with those of the linear poly(ethylene glycol)s under the same conditions. The proton NMR relaxation times (T 1 and T 2) were measured to study the mobility of the dendrimer core part and terminal group as a function of the dendrimer size.

Scaling trend in diffusion coefficients of low generation G0–G3 PAMAM dendrimers in aqueous solution at high and neutral pH

“…According to our results, protonated PAMAM dendrimers behaves as predicted by the Zimm's model in a h solvent, whereas neutral species show a scaling exponent (-0.39) corresponding to a poor solvent condition where the self-interaction between dendrimer branches is preferred over solute-solvent interactions [32]. Similar scaling exponents have been reported for neutral dendrimers from both [20,32] and theoretical [17] approaches. The observed scaling trend at pH 12 indicates that neutral dendrimers experience a considerable degree of inward folding, which has been reported to increase with the dendrimer generation [33].…”

“…First experimental reports dealing with dendrimer diffusion were based on DOSY experiments on poly(propyleneimine) dendrimers in poly(vinyl alcohol) at different conditions of concentration and temperature, showing that the self-diffusion coefficients decrease with increasing molecular size, and with a decreasing temperature. This study also showed a decrease in the dendrimer hydrodynamic radii with decreasing temperature [20].…”

Treatment of dyeing wastewater by activated carbons derived from municipal sewage sludge

“…The terminal groups are not crowded because the generalized order parameter ( S 2 ) remains very low for the methyl group even for the larger dendrimers. Moreover, a diffusion study has demonstrated a density distribution between a fractal structure and a uniform density distribution 29…”

Structure and dynamics of poly(carbosilane) dendrimers as revealed by pulsed field gradient NMR technique

“…Pulsed field gradient nuclear magnetic resonance (PFG NMR) became the method of choice, among other physical techniques, to characterize the dendrimer structural and translational mobility [1][2][3][4][5][6][7][8][9]. This technique gives the opportunity to measure directly molecular self-diffusion coefficients in dendrimer solutions starting from the polymer in block (the dendrimer itself).…”

“…The dendrimer self-diffusion may be characterized by a single self-diffusion coefficient dependent on the concentration [3][4][5][6][7][8][9]. In this case, the dendrimer solutions are homogeneous systems without any macromo[ecular associations and the self-diffusion coefficient is determined by the translational motion of separate macromolecules.…”