Intramolecular Dynamics of Dendrimers under Excluded-Volume Conditions

Ganazzoli, Fabio; Ferla, Roberto La; Raffaini, Giuseppina

doi:10.1021/ma001613z

Cited by 70 publications

(89 citation statements)

References 26 publications

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“…Thus, if D = a and G = b we shall briefly denote such a dendrimer as DaGb as in Refs. 19,20. Then the total number of monomers will be,…”

Section: Model and Notationsmentioning

confidence: 99%

“…Based on this approach the dynamic properties such as the relaxation times spectrum, dynamic structure factor and the viscoelastic moduli, 20 , as well as the inter-chain theta-temperature 21 have been also investigated. Unfortunately, constraints of the numerical procedure employed limited such studies to dendrimers with D = 1, 2 spacers only.…”

Section: Introductionmentioning

confidence: 99%

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Conformations of dendrimers in dilute solution

Timoshenko

Kuznetsov

Connolly

2002

The Journal of Chemical Physics

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Conformations of isolated homo-dendrimers of G = 1 − 7 generations with D = 1 − 6 spacers have been studied in the good and poor solvents, as well as across the coil-to-globule transition, by means of a version of the Gaussian self-consistent (GSC) method and Monte Carlo (MC) simulation in continuous space based on the same coarse-grained model. The latter includes harmonic springs between connected monomers and the pair-wise Lennard-Jones potential with a hard core repulsion. The scaling law for the dendrimer size, the degrees of bond stretching and steric congestion, as well as the radial density, static structure factor, and asphericity have been analysed. It is also confirmed that while smaller dendrimers have a dense core, larger ones develop a hollow domain at some separation from the centre.PACS numbers: 36.20.Ey, 61.25.Hq

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“…Thus, if D = a and G = b we shall briefly denote such a dendrimer as DaGb as in Refs. 19,20. Then the total number of monomers will be,…”

Section: Model and Notationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Conformations of dendrimers in dilute solution

Timoshenko

Kuznetsov

Connolly

2002

The Journal of Chemical Physics

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“…Recent theoretical work indicates that this should also be true for dendritic polymers. 21,22 The aim of this work is to find a consistent correlation between the structure of the dendrimers and their dynamic behavior.…”

Section: Introductionmentioning

confidence: 99%

“…For dendrimers of various branching topology, local stiffness, and different generations, La Ferla 21 and Ganazzoli et al 22 calculated the dynamic structure factor in the framework of the Rouse-Zimm theory. Compared to star polymers, the model predicts an even deeper local minimum located at qR g Ϸ2.08 for the reduced relaxation rate, except for dendrimers with high local stiffness.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of star-burst dendrimers in solution in relation to their structural properties

Rathgeber

Monkenbusch

Kreitschmann³

et al. 2002

The Journal of Chemical Physics

133

160

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We have measured both the static and dynamic structure factors of a single dendrimer with small-angle x-ray scattering ͑SAXS͒ and neutron spin-echo spectroscopy under good solvent conditions with the aim of finding a consistent correlation between the structural properties of dendrimers and their dynamic behavior. The samples under investigation were star-burst polyamidoamine dendrimers with generations gϭ0 to 8 in dilute methanol solutions. A model independent approach employing inverse Fourier transformation and square root deconvolution methods has been used to analyze the SAXS data to obtain the pair distance distribution function p(r) and the radial excess electron density profile ⌬ (r). In addition, we formulated a model that takes both the colloidal ͑globular, compact shape with form polydispersity or fuzzy surface͒ as well as the loose, polymeric ͑self-avoiding random walk͒ character of dendrimers into account. With this model we were able to describe the spectra of all dendrimer generations consistently. Parameters discussed as a function of the dendrimer generation are, among others, the correlation length of the density fluctuations ͑blob radius͒ , the radius of gyration R g , the sphere radius R s , the form polydispersity s or analogously, the width of the fuzzy surface region 2 f . Both the model-independent approach and the model fits reveal that at least down to the third generation the dendrimers exhibit a rather compact, globular shape. These findings are in agreement with the dynamic results obtained by NSE spectroscopy which probes length scales both larger and much smaller than the dimension of a single dendrimer. The method reveals that the dynamics throughout is dominated by the center-of-mass diffusion-the internal dynamics is suppressed. The diffusion coefficients obtained are close to the values calculated from the Stokes-Einstein relation using the sphere radius R s determined from the SAXS spectra. Dynamically, the dendrimers behave like ''hard'', solid spheres.

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“…The above classification can be extended to the case of P > 1 dendrimers. 27) In the present study, we focus on the relaxation time of the antisymmetric mode corresponding to the relative motion of two branches grafted to a common branching segment in each generation. Let the relaxation time for the ðG À k þ 1Þth generation be denoted by GÀkþ1 , where k ¼ 1; 2; .…”

Section: Relaxation Processes Of Dendrimersmentioning

confidence: 99%

Relaxation of a Single Dendrimer

Iwaoka

Takano

2013

J. Phys. Soc. Jpn.

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Relaxation process of a single dendrimer with excluded volume effects is studied in the free-draining limit for various parameters characterizing the architecture of the dendrimer, which are the functionality of central segment f c , the functionality of branching segments f , the number of generations G and the number of bonds in each spacer between branching segments P. By assuming that the dendrimer relaxes hierarchically from the outermost generation to the central segment after relaxation of the spacers, a scaling law 1 $ f 1À c fð f À 1Þf 1À g GÀ1 P 2 þ1 for the longest relaxation time 1 is derived, where % 0:588 is the Flory exponent. Another scaling law for relaxation times of other antisymmetric relaxation modes is also derived. In order to verify the scaling laws, Brownian dynamics simulations of a single dendrimer are performed and relaxation times are estimated by the relaxation mode analysis method. The scaled relaxation time 1 =ð f 1À c P 2 þ1 Þ is proportional to fð f À 1Þf 1Àx g GÀ1 , where the exponent x corresponding to is estimated as x % 0:66 for f ¼ 3 and 0.63 for f ¼ 4. It is found that 1 =ð f 1À c fð f À 1Þf 1Àx g GÀ1 Þ / P 2yþ1 , where the exponent y that corresponds to is estimated as y % 0:58. The agreement with the predicted scaling law becomes better as G and f becomes larger, where the concentration of segments becomes larger. The other scaling law for other antisymmetric relaxation modes is also verified.

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Intramolecular Dynamics of Dendrimers under Excluded-Volume Conditions

Cited by 70 publications

References 26 publications

Conformations of dendrimers in dilute solution

Conformations of dendrimers in dilute solution

Dynamics of star-burst dendrimers in solution in relation to their structural properties

Relaxation of a Single Dendrimer

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