Dendritic polymers characterization

Dendrons and dendrimers are the most intensely investigated subset of dendritic polymers. In the past decade over 2000 literature references have appeared on this unique class of structure controlled polymers. The term dendrimer was coined by Tomalia, et al. over 15 years ago in the first reports on poly(amidoamine) (PAMAM) dendrimers [75, 76]. It is derived from the Greek words dendri-(branch tree-like) and meros - part of). Poly(amidoamine) dendrimers constitute the first dendrimer family to be commercialized and undoubtedly represent the most extensively characterized and best understood series at this time. In view of the extensive literature information in this area, much of the remaining overview will focus on PAMAM dendrimers and will... 

The synthesis of well-defined LCB polymers have progressed considerably beyond the original star polymers prepared by anionic polymerization between 1970 and 1980. Characterization of these new polymers has often been limited to NMR and SEC analysis. The physical properties of these polymers in dilute solution and in the bulk merit attention, especially in the case of completely new architectures such as the dendritic polymers. Many other branched polymers have been prepared, e.g. rigid polymers like nylon [123], polyimide [124] poly(aspartite) [125] and branched poly(thiophene) [126], There seems to be ample room for further development via the use of dendrimers and hyperbran-... 

Atomic Force Microscopy for the Characterization of Dendritic Polymers and Assemblies... 

Grohn, F., Bauer, B. J. and Amis, E. J. Characterization, modelling and applications of dendritic polymers, in Abstracts to the NIST Workshop on Properties and Applications of Dendritic Polymers. National Institute of Standards and Technology, Gaithersburg, MD, USA, 1998. 

The solid-phase synthesis of dendritic polyamides was explored by Frechet et al. [49]. Inspired by the technique used by Merrifield for peptide synthesis, the same strategy was used to build hyperbranched polyamides onto a polymeric support. The idea was to ensure the preservation of the focal point and to ease the purification between successive steps. The resulting polymers were cleaved from the solid support, allowing ordinary polymer characterization. The reaction was found to be extremely sluggish beyond the fourth generation. 

Photochromic dendritic polymers 74 considered as optical memory elements were characterized (08CC5755). 

In the beginning, the term dendrimer , which was established by Tomalia in 1985 [42,43], described all types of dendritic polymers. Later a distinction based on the relative degree of structural control present in the architecture was drawn. Nowadays, many other types of dendritic architectures are known, even if most of them, however, have not yet been widely investigated and fully characterized. The term dendritic polymer involves four substructures (Fig. 2), namely dendrimers themselves, dendrons, random hyperbranched polymers, and dendrigraft polymers [44, 45],... 

Dendritic macromolecules exhibit compact globular structures which lead to their low viscosity in the melt or in solution. Furthermore, dendritic macromolecules are characterized by a very large number of available functional groups, which lead to unprecedented freedom for changing/tuning/tailoring the properties of these multivalent scaffolds via complete or partial derivatization with other chemical moieties. All these features have contributed to multidisciplinary applications of these unique macromolecular structures in recent years 6, 7). The development of efficient synthetic routes in recent years has given rise to a virtually unlimited supply of commercially available dendritic polymers, at very affordable price. The transport properties of hyperbranched and dendritic polymers have recently attracted attention as potentially new barrier and membrane materials 8-9). 

As a result of their ease of solubility, characterization of dendritic materials can be readily achieved by means of standard polymer characterization techniques, such as NMR and GPC. However, despite the excellent characterization that pervades the materials discussed in this chapter, it should be noted that with the widespread introduction of mass spectrometric techniques which can characterize such macromolecules, the structural perfection assumed in many depictions of dendrimers have been shown to be highly idealized. Indeed, spectrometric analysis of many samples has revealed that imperfections and defects are, in fact, very common. In this section, organometallic dendrimers, a subset of metallodendrimers, are discussed. 

In 1979, while working for Dow Chemical Co., Donald A. Tomalia discovered Starburst dendrimers, which are poly(amidoamine) (PAMAM) dendrimers prepared by a so-called divergent synthesis [25]. These structures are some of the best characterized and most extensively utilized dendritic polymers in the field of bioscience. Other widely known den-drimer structures are polyethers, which were reported in 1990 by Frdchet [26], and poly(propylene imine) (PPI) dendrimers from the groups of Womer and Miilhaupt [27] and de Brabander-van den Berg and Meijer [28]. Smaller PPI dendrons were described by Vogtle et al. already in 1978 [29]. 

Recent advances in the development of drug dehvery research area have led to the need for the production of weU-defined and characterized nanoparticulates. Especially the particle size and size polydispersity are important factors which influence the distribution of the particles within the body and their interaction and uptake by hving cells [1 ]. Colloidal carriers such as liposomes, micelles, dendritic polymers, and nanoparticles are the most promising candidates in regards to the site-specific delivery and controlled dmg release. Core-shell particles with a liquid core have gained increased attention in the past years owing to their utilization as sub-p.m containers for the encap-... 

N.J. Turro, W. Chen, and M.F. Ottaviani. Characterization of dendrimer structures by spectroscopic techniques, in Dendrimers and Other Dendritic Polymers. J.M.J. Frechet and D.A. Tomalia, Eds. John Wiley Sons West Sussex, pp. 309-330, 2001. 

Tomalia DA, Swanson DR (2001) Laboratory synthesis and characterization of megamers core-shell tecto(dendrimers). In Frechet JMJ, Tomalia DA (eds) Dendrimers and other dendritic polymers. Wiley, Chichester, pp 617-629... 

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