Dendrimer characterisation

Whereas solid-state NMR spectroscopy [19] (see Section 7.6.3.2) plays only a minor role in dendrimer characterisation, one-dimensional (lD-)NMR spectroscopy of dendrimers in solution still serves as a routine method in such characterisation. 

Poly(e caprolactone) gamma substituted with benzylidene, 2,2-bis(oxymethyl) propionate Dendrimer characterisation [133]... 

FTIR-MALDI polymer and dendrimer characterisation and structure isotacticity, cyclo and oligolactides, polymerisation kinetics, molecular weight evaluations, diblock polymers-oligomer studies and cis-trans structures. 

Like PAMAM dendrimers, polylysine dendrimers are largely characterised by amide bonds. They attracted interest as potential therapeutic agents for use in boron neutron capture therapy and in magnetic resonance imaging (MRI) (see Chapter 8), since dendritic polylysines apparently have a lower toxicity than their linear counterparts. The polylysine shown in Fig. 4.10 with a total of 80 terminal boron atoms in the carborane units and a dansyl group was designed specifically for boron neutron capture therapy [20]. 

J. R. Baker Jr., Synthesis and Characterisation of Novel POPAM-PAMAM (POMAM) Hybrid Dendrimers as a Building Block in Nanotechnology. http //www.forsight.org/conferences/... 

Mention of chirality in dendritic architectures can be traced back to patents of Denkewalter et al., which describe the construction of peptide-like dendritic structures from L-lysine units [1]. In spite of the demanding nature of some of these syntheses, numerous chiral dendritic structures have meanwhile been prepared and characterised [2]. This cannot be explained solely by the somewhat academic interest in the effect of chiral monomeric building blocks on the chirality of the overall molecule. The prospect of using chiral dendrimers as model... 

Modification of the electrochemical properties of a redox centre surrounded by dendritic fragments [93] can lead to two different dendritic effects. The first one is manifested in a shift of the redox potentials, the extent and direction depending upon the dendritic architecture and the solvent. Such behaviour was observed in dendritic iron-porphyrins [94]. The second effect is apparent in a delay of redox transfer kinetics and is characterised by a stepwise increase in the distance between the peaks in a cyclovoltammogram with increasing dendrimer generation number. 

Recent studies have shown that RP-HPLC in combination with MALDI-TOF mass spectrometry is suitable for preparative separation and characterisation of PAMAM dendrimers of different generations or with different peripheral groups [8]. Investigations performed so far indicate that the purity of a dendri-... 

Multidimensional NMR spectroscopy ((2D)-NMR, (3DJ-NMR) is also acquiring increasing importance in the characterisation of dendrimers. On inclusion of a... 

Diffusions NMR spectroscopy (e.g. PGSE = Pulsed Gradient Spin Echo STE = Stimulated Echo DOSY = Diffusion Ordered Spectroscopy) is a straightforward and accurate method for determination of the self-diffusion coefficient of a molecule. Its principal use in dendrimer chemistry is for size determination of dissolved dendrimers since the self-diffusion coefficient is directly correlated with the hydrodynamic radius of the molecule via the Stokes-Einstein equation [24]. Although one-dimensional and multidimensional diffusion NMR experiments can thus make an important contribution to structural characterisation of dendrimers, they have been used comparatively rarely until recently [25, 26]. 

Chiroptical methods used in dendrimer research exploit the optical activity as a characteristic property of chiral dendrimers for characterisation of their structures. 

The following summary provides an overview of the properties and specific questions to be addressed in connection with the characterisation of dendrimers, and lists the appropriate analytical techniques. 

Roovers, J., Comanita, B. Dendrimers and Dendrimer-Polymer Hybrids. Vol. 142, pp 179-228. Rothon, R. N. Mineral Fillers in Thermoplastics Filler Manufacture and Characterisation.Vol. 139, pp. 67-108. 

Characterisation of dendrimers, especially determination of the dendritic purity (percentage of defect free dendrimer), is difficult because of their large size and high symmetry. Techniques such as NMR... 

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