Starburst dendrimers. 5. Molecular shape control

Naylor, Adel M.; Goddard, William A.; Kiefer, Garry E.; Tomalia, Donald A.

doi:10.1021/ja00188a079

Cited by 505 publications

(405 citation statements)

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“…Naylor et al 22 have discussed the MD simulation of PAMAM (poly(amido-amine)) dendrimers. This study, albeit generally interesting, could cover a timescale of hundreds of picoseconds only.…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

Conformations of dendrimers in dilute solution

Timoshenko

Kuznetsov

Connolly

2002

The Journal of Chemical Physics

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“…De Gennes and Hevert [32] developed a self-consistent ®eld model which predicts a dendrimer structure emanating radially outward with a density pro®le minimum at the center of the dendrimer where all the terminal groups are on the periphery of the macromolecule and the ideal dendritic growth will only occur until a certain generation is reached at which point steric congestion will prevent further growth. Molecular modeling performed by Goddard et al [4,34] predicts internal cavities, most of the terminal Fig. 7.…”

Section: Methods Calculations Results and Analysismentioning

confidence: 99%

Theoretical models of hyperbranched polymers

Perez

Longo

Taft

2000

Journal of Molecular Structure: THEOCHEM

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We have investigated linear, starbranched and hyperbranched X n H m polymers and determined the number of atoms, rotors, internal coordinates, valence and HOMO molecular orbitals as well as molecular mass for each generation and valency. We use the semi-empirical MNDO model to obtain full geometry optimization for increasingly larger clusters for each generation in order to obtain total relative energies. We then generate analytical functions, which correlate the total relative energies with the generation, for each valency, for the hyperbranched polymers. We have also generated analytic functions, which correlate total relative energies, experimental van der Waals coef®cients and standard enthalpy of combustion with the number of carbon atoms in each chain of the linear alkanes. These results are used to predict the enthalpy of combustion for higher generations of alkanes in good agreement with experiment. Due to the exponential increase in size with generation of the hyperbranched polymers alternative analytical models may be of interest to theoretical chemists working in this line of research. q

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“…Because N increases almost geometrically as G increases, single dendrimers might be expected to have a conformation with a hollow core and crowded peripheries, as reported in the early theoretical work by de Gennes and Hervet. 9) However, recent studies [10][11][12] suggest an opposite structure that has a dense core and back-folding branches: Single dendrimers can become highly packed molecule.…”

Section: Introductionmentioning

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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Starburst dendrimers. 5. Molecular shape control

Abstract: The recently reported "starburst dendrimer"1,2 and "arborol"3 systems provide unimolecular prototypes that allow for both endo-receptor and exo-supramolecular controlled molecular morphogenesis.9 This present communication describes the use

Cited by 505 publications

References 3 publications

Conformations of dendrimers in dilute solution

Conformations of dendrimers in dilute solution

Theoretical models of hyperbranched polymers

Relaxation of a Single Dendrimer

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