Probing the onset of dense shell packing by measuring the aminolysis rates for a series amine terminated dendrimers

Burnett, J.; King, Amy S. H.; Twyman, Lance J.

doi:10.1016/j.reactfunctpolym.2005.07.022

Cited by 14 publications

(17 citation statements)

References 19 publications

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“…During these experiments the initial rate of aminolysis steadily increased with dendrimer size, up to the third generation (32 terminal groups), before dramatically decreasing for the larger fourth‐generation dendrimer (64 terminal groups) 26. These results were interpreted as the onset of a densely packed sterically crowded dendrimeric structure 27…”

Section: Resultsmentioning

confidence: 93%

Synthesis and aggregation of amine‐cored polyamidoamine dendrons synthesised without invoking a protection/deprotection strategy

King

Martin

Twyman

2006

Polymer International

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The synthesis of a series of amine‐cored N,N‐dimethyl‐terminated polyamidoamine dendrons with the potential to be modified at their focal point is reported. The use of an aniline core enables the target molecules to be synthesised without resorting to the use of a time‐consuming and expensive protection/deprotection strategy. After synthesising these molecules significant frothing in aqueous solution at millimolar concentrations was noticed, a property associated with aggregation. The critical micelle concentrations were therefore measured and found to occur at relatively low dilutions (in the range 10−4–10−5 mol L−1). Copyright © 2006 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 93%

Synthesis and aggregation of amine‐cored polyamidoamine dendrons synthesised without invoking a protection/deprotection strategy

King

Martin

Twyman

2006

Polymer International

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“…The structure of dendrimers has received considerable interest 5. 36, 72–87 In comparison with the classical PAMAM dendrimers,88 we would expect less conformational freedom around the core in the PD analogues owing to the electronic interaction between the two N atoms and the atoms in the aromatic ring, which for R larger than Me results in a planar arrangement around N and a C Ar (2)‐C Ar (1)‐N‐C(1) dihedral angle of about 7°. On the other hand, the preferred conformer for R=Me (TMePD) has a pyramidal arrangement around the N atom, although the energy difference between the pyramidal and the planar conformers is only 0.0012767 a.u.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical One‐Electron Oxidation of Low‐Generation Polyamidoamine‐Type Dendrimers with a 1,4‐Phenylenediamine Core

et al. 2009

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A series of polyamidoamine (PAMAM)-type dendrimers with a 1,4-phenylenediamine (PD) core is prepared from PD by procedures including Michael addition of methyl acrylate followed by aminolysis with 1,2-ethanediamine. Their one-electron oxidation potentials are determined by differential pulse voltammetry (DPV) in methanol, acetonitrile, dichloromethane, and dimethyl sulfoxide. The dendrimers are more difficult to oxidize than N,N,N',N'-tetramethyl-p-phenylenediamine (TMePD). The oxidation potentials decrease with increasing dendrimer generation up to G0.5, after which the potential is essentially constant up to G2.0. The structures of both the neutral species and the radical cations are studied by DFT calculations at the B3LYP/6-31G(d,p) level of theory, which include a series of simple PDs for comparison. The data show that the structural arrangement close to the PD core is similar to that of N,N,N',N'-tetra-n-alkyl-p-phenylenediamines, including a planar arrangement of the atoms linked to the two PD nitrogen atoms. Thus, the effect of chain size on the oxidation potential appears to be caused primarily by a simple electronic effect. The calculations indicate considerable reorientation of the dendrimer side chains on oxidation, presumably caused by interactions between the positive charge centered at the core and the neighboring ester or amide dipoles. The relative ease of oxidation of TMePD and the lowest members of the series of the dendrimers can be reproduced theoretically only when solvation was included in the calculations. The DPV peak heights vary approximately as predicted from the Stokes-Einstein-Sutherland equation, but the variation of the relative effective radii with the size of the dendrimer is much larger than predicted from the radii obtained by the DFT calculations, that is, the dendrimers exist in solution mainly as aggregates.

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“…Twyman et al studied aminolysis of p-nitrophenyl acetate with primary amines at the surface of polyamidoamine (PAMAM) dendrimers (Fig. 9) 49,50 The ca. 30-fold rate acceleration observed for generation 4 dendrimer was explained as a combination of several factors.…”

Section: Pre-concentration (Solvent Effect)mentioning

confidence: 99%

Reactivity in organised assemblies

Chechik

2006

Annu. Rep. Prog. Chem., Sect. B: Org. Chem.

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This article discusses the application of physical organic chemistry tools to probe reactions in organic ''superstructures'', including colloidal systems, dendrimers, nanoparticles, mono-and multilayers. Despite the diversity of the systems, the inherent mechanistic principles are the same as for single molecule chemistry, and the following review attempts to decipher the main effects that should be considered when studying reactivity in the organised assemblies.

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Probing the onset of dense shell packing by measuring the aminolysis rates for a series amine terminated dendrimers

Cited by 14 publications

References 19 publications

Synthesis and aggregation of amine‐cored polyamidoamine dendrons synthesised without invoking a protection/deprotection strategy

Synthesis and aggregation of amine‐cored polyamidoamine dendrons synthesised without invoking a protection/deprotection strategy

Electrochemical One‐Electron Oxidation of Low‐Generation Polyamidoamine‐Type Dendrimers with a 1,4‐Phenylenediamine Core

Reactivity in organised assemblies

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