Chain dynamics in poly(amidoamine) dendrimers: a study of proton NMR relaxation parameters

Meltzer, Antje; Tirrell, David A.; Jones, Alan A.; Inglefield, Paul T.; Hedstrand, David M.; Tomalia, Donald A.

doi:10.1021/ma00044a014

Cited by 88 publications

(81 citation statements)

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“…Solid state NMR was used to elucidate the highly restricted motions which are allowed within the scaffolds of polyphenylene dendrimers, [25,31], and these data provide sound proof of the feasibility of the assumptions underlying the modeling of our scattering data. Since the pioneering study of Meltzer et al on rapid arm fluctuations in poly(amido amine) dendrimers by solution-state NMR relaxation [32,33], which yielded conclusive evidence of an absence of dense-shell packing, solid-state NMR has emerged as another important method to characterize dendron structure [34] and mobility [35]. We know of no other investigation, however, in which SANS-data have been combined with NMR results.…”

Section: Comparison With Data Obtained From Solid State Nmrmentioning

confidence: 99%

Analysis of the spatial structure of rigid polyphenylene dendrimers by small-angle neutron scattering

Rosenfeldt

Dingenouts

Pötschke

et al. 2005

Journal of Luminescence

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Section: Comparison With Data Obtained From Solid State Nmrmentioning

confidence: 99%

Analysis of the spatial structure of rigid polyphenylene dendrimers by small-angle neutron scattering

Rosenfeldt

Dingenouts

Pötschke

et al. 2005

Journal of Luminescence

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“…NMR [46,51,59,60], neutron scattering [61][62][63], dielectric relaxation spectroscopy [64,65], rheology [66], fluorescence anisotropy [67], and molecular and Brownian dynamics computation [68][69][70][71] have provided some information about the mobility of the different segments constituting a dendrimer, generally via the rotational correlation time (τ C ) of the segments. The overall conclusion of these studies is that the chain ends are more mobile than the internal segments, and that their rotational correlation time is not much affected by increasing G values.…”

Section: Introductionmentioning

confidence: 99%

Internal Dynamics of Dendritic Molecules Probed by Pyrene Excimer Formation

Duhamel

2012

Polymers

147

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Abstract:This review exposes the current poor understanding of the internal segmental chain dynamics of dendrimers in solution probed by monitoring the process of excimer formation between pyrene labels covalently attached to the chain ends of dendrimers. The review begins by covering the bases of fluorescence and the kinetics of pyrene excimer formation before describing a procedure based on the Model Free (MF) analysis that is used to analyze quantitatively the fluorescence decays acquired for dendrimers, the ends of which have been fully and covalently labeled with pyrene. Comparison of the various trends obtained by different research groups describing the efficiency of pyrene excimer formation with the generation number of dendrimers illustrates the lack of consensus between the few studies devoted to the topic. One possible reason for this disagreement might reside in the presence of minute amounts of unattached pyrene labels which act as potent fluorescent impurities and affect the analysis of the fluorescence spectra and decays in an uncontrolled manner. The review points out that the MF analysis of the fluorescence decays acquired with pyrene-labeled dendrimers enables one to account for the presence of unattached pyrene and to retrieve information about the internal segmental dynamics of the dendrimer. It provides guidelines that should enable future studies on pyrene-labeled dendrimers to yield results that are more straightforward to interpret.

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“…NMR spectroscopy has also been employed to characterize the structure of PAMAM dendrimers of different generation, by means of extensive studies on 1 H, 13 C, and 15 N chemical shifts, providing a valuable means for their characterization [12][13][14]. On the other hand, spin-lattice T1 and spin-spin T2 relaxation times have been measured to determine the chain mobility of G1-G8 PAMAM dendrimers, showing that segmental motion is faster at the dendrimer surface [15,16]. Other structural studies on low and high generation PAMAM dendrimers rely on coarse grained and fully atomistic molecular dynamic simulations, which have shown an increase in the radius of gyration as a consequence of dendrimer protonation [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

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

2011

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Aqueous solution diffusion coefficients for G0-G3 PAMAM dendrimers were determined from DOSY-NMR spectroscopy at high and neutral pH. The study was performed in a dilute regime and diffusion coefficients at infinite dilution (D 0 ) were estimated from the variation of diffusion coefficients with dendrimer concentration. Hydrodynamic radii (R h ) for each dendrimer were estimated from D 0 using the Stoke-Einstein relationship at both pH. According to D 0 and R h values, the structure of G0-G1 PAMAM dendrimers is almost insensitive to pH variations, whereas G2-G3 PAMAM dendrimers undergo swelling at neutral pH, due to surface amino groups protonation. Experimental diffusion coefficients show a scaling trend with the number of dendrimer atoms (N), with scaling laws of the type D 0 / N a , where a takes values of -0.39 and -0.50 at pH 12 and 7, respectively. For the first time, experimental data accounts for the scaling behavior of aqueous diffusion coefficients for low generation PAMAM dendrimers, as previously reported from molecular dynamics simulations.

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Chain dynamics in poly(amidoamine) dendrimers: a study of proton NMR relaxation parameters

Cited by 88 publications

References 1 publication

Analysis of the spatial structure of rigid polyphenylene dendrimers by small-angle neutron scattering

Analysis of the spatial structure of rigid polyphenylene dendrimers by small-angle neutron scattering

Internal Dynamics of Dendritic Molecules Probed by Pyrene Excimer Formation

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

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