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Structure of PAMAM Dendrimers: Generations 1 through 11

Maiti, Prabal K. and Çağin, Tahir and Wang, Guofeng and Goddard, William A., III (2004) Structure of PAMAM Dendrimers: Generations 1 through 11. Macromolecules, 37 (16). pp. 6236-6254. ISSN 0024-9297.

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The structure and dynamics of poly(amido amide) (PAMAM) dendrimers have been of great interest both scientifically and industrially, but such important features as the distributions of atoms, channels, and strain inside these molecules remain unresolved. This paper reports results from systematic investigations of the atomistic structure of ethylenediamine (EDA) cored PAMAM dendrimer up through the 11th generation (294 852 atoms), at which point the strain energy has risen to a point that limits uniform growth of additional layers. Here we report, as a function of generation, structural properties such as radius of gyration, shape tensor, asphericity, fractal dimension, monomer density distribution, solvent accessible surface area, molecular volume, and end group distribution functions, all evaluated from extensive molecular dynamics (MD) at 300 K. We find that the radius of gyration scales as Rg ∼ N1/3 over the entire range of generations, suggesting rather uniform space filling for all generations. Contrary to common expectation, we find that the outer subgenerations penetrate substantially into the interior of the dendrimer, even for G11. Consequently, the terminal amine groups are distributed throughout the interior, not just on the periphery of the dendrimer. However for G6 through G11 there is a large region of uniform density, supporting the uniform scattering model often used in interpreting the SANS (small-angle neutron scattering) and SAXS (small-angle X-ray scattering) data, which lead to sizes in excellent agreement with the calculations. The calculated single particle form factor approaches that of a sphere as the generation number increases. For the larger generations, we found that the use of continuous configuration biased Monte Carlo (CCBB MC) was essential to construct initial configurations that lead to lower final strain energies.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Çağin, Tahir0000-0002-3665-0932
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2004 American Chemical Society. Received 29 October 2003. Published online 13 July 2004. Published in print 1 August 2004. We thank Dr. Mamadou Diallo for many helpful discussions. This research was initiated with a support from the U. S. Army Research Office under Grant No. DAAG55-97-1-0126. The MSC facilities used in these studies were funded by grants from ARO (DURIP), ONR (DURIP), NSF (MRI), and IBM (SUR). The MSC is also supported by grants from NIH, NSF, DOE, Chevron Texaco, General Motors, Seiko Epson, Asahi Kasei, and the Beckman Institute.
Funding AgencyGrant Number
Army Research Office (ARO)DAAG55-97-1-0126
Office of Naval Research (ONR)UNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Issue or Number:16
Record Number:CaltechAUTHORS:20170724-090640790
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Official Citation:Structure of PAMAM Dendrimers:  Generations 1 through 11 Prabal K. Maiti, Tahir Çaǧın, Guofeng Wang, and William A. Goddard, III Macromolecules 2004 37 (16), 6236-6254 DOI: 10.1021/ma035629b
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79288
Deposited By: Ruth Sustaita
Deposited On:24 Jul 2017 16:36
Last Modified:03 Oct 2019 18:18

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