Chain dynamics in poly(amidoamine) dendrimers: a study of carbon-13 NMR relaxation parameters

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

doi:10.1021/ma00044a013

Cited by 161 publications

(177 citation statements)

References 4 publications

(7 reference statements)

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“…Relaxation studies of PAMAM, PPI, and polyaryl ether dendrimers show that the exterior of the dendrimer has more mobility and the interior of the dendrimer. 15,16,21,25,28 Our system not only agrees with these studies but also provides evidence that each layer of the dendrimer has different mobilities.…”

Section: Resultssupporting

confidence: 89%

Conformational Analysis of Triazine Dendrimers: Using NMR Spectroscopy To Probe the Choreography of a Dendrimer’s Dance

Moreno

Simanek

2008

Macromolecules

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One-dimensional (1D) and two-dimensional (2D) NMR studies are used to probe the conformation of a melamine dendrimer bearing unique NMR signals from the core to the periphery. Four conceptual anchors for dendrimer conformation emerge from these experiments. First, changes in isomer populations observed by 1 H NMR reveal the onset of globular structure. Second, NOE complexity emerges with globular structure: variable temperature NOESY studies show that the peripheral groups, BOC-protected aliphatic amines, fold back into the globular core of the macromolecule at 75 °C in DMSO-d 6 . Third, variable temperature coefficients measured for NH protons suggest that solvent is largely excluded from the interior of the dendrimer: the carbamate NH groups of the periphery are most sensitive to temperature while the NHs nearest the core show little temperature dependence. Conformation is influenced by solvent choice: backfolding is observed in DMSO-d 6 , but not in either CDCl 3 or CD 3 OD. Finally, relaxation studies show that peripheral groups are more dynamic than groups at the core. These anchors consolidate observations made by many groups on disparate systems within a common architecture.

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Section: Resultssupporting

confidence: 89%

Conformational Analysis of Triazine Dendrimers: Using NMR Spectroscopy To Probe the Choreography of a Dendrimer’s Dance

Moreno

Simanek

2008

Macromolecules

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“…This conjecture is also consistent with the conclusion of NMR experiment conducted by Meltzer and coworkers. 40 Subtracting the intra-dendrimer water distribution presented in Fig. 4 from the total scattering length density distribution shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Spatial distribution of intra-molecular water and polymeric components in polyelectrolyte dendrimers revealed by small angle scattering investigations

et al. 2011

The Journal of Chemical Physics

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An experimental scheme using contrast variation small angle neutron scattering technique is developed to investigate the structural characteristics of amine-terminated poly(amidoamine) dendrimers solutions. Using this methodology, we present the dependence of both the intra-dendrimer water and the polymer distribution on molecular protonation, which can be precisely adjusted by tuning the pH of the solution. Assuming spherical symmetry of the spatial arrangement of the constituent components of dendrimer, and that the atomic ratio of hydrogen-to-deuterium for the solvent residing within the cavities of dendrimer is identical to that for the solvent outside the dendrimer, the intradendrimer water distribution along the radial direction is determined. Our result clearly reveals an outward relocation of the peripheral groups, as well as enhanced intra-dendrimer hydration, upon increasing the molecular protonation and, therefore, allows the determination of segmental backfolding in a quantitative manner. The connection between these charge-induced structural changes and our recently observed progressively active segmental dynamics is also discussed.

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“…At the same time their relaxation properties, which are very important for many practical applications, are poorly understood. [9][10][11][12][13] Computer simulation [14][15][16][17][18][19][20][21][22] is one of the perspective methods to study the dendrimer relaxation properties. Obtained simulation results correlate well with the existing experimental data on large-scale relaxation processes, such as diffusion 14 and intrinsic viscosity.…”

Section: Introductionmentioning

confidence: 99%

Orientational mobility and relaxation spectra of dendrimers: Theory and computer simulation

Markelov

Gotlib²,

Lyulin³

et al. 2009

The Journal of Chemical Physics

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The developed theory of the orientational mobility of individual segments of a perfectly branched dendrimer is used to calculate the relaxation spectrum of a dendrimer. Frequency dependences of NMR relaxation 1 / T 1 and of the nuclear Overhauser effect have been theoretically calculated from the Brownian dynamics simulation data. The dendrimer segmental orientational mobility is governed by three main relaxation processes: ͑i͒ the rotation of the dendrimer as a whole, ͑ii͒ the rotation of the dendrimer's branch originated from a given segment, and ͑iii͒ the local reorientation of the segment. The internal orientational mobility of an individual dendrimer segment depends only on the topological distance between this segment and the terminal shell of the dendrimer. Characteristic relaxation times of all processes and their contributions to the segmental mobility have been calculated. The influence of the number of generations and the number of the generation shell on the relaxation times has been studied. The correlation between the characteristic times and the calculated relaxation spectrum of the dendrimer has been established.

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Chain dynamics in poly(amidoamine) dendrimers: a study of carbon-13 NMR relaxation parameters

Cited by 161 publications

References 4 publications

Conformational Analysis of Triazine Dendrimers: Using NMR Spectroscopy To Probe the Choreography of a Dendrimer’s Dance

Conformational Analysis of Triazine Dendrimers: Using NMR Spectroscopy To Probe the Choreography of a Dendrimer’s Dance

Spatial distribution of intra-molecular water and polymeric components in polyelectrolyte dendrimers revealed by small angle scattering investigations

Orientational mobility and relaxation spectra of dendrimers: Theory and computer simulation

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