POLYMER SCIENCE

Growing Large Molecules

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Science  22 Jun 2001:
Vol. 292, Issue 5525, pp. 2219
DOI: 10.1126/science.292.5525.2219c

Dendrimers, also known as cascade molecules, are polymers in which several layers of highly branched repeating units emanate from a central core. Two synthetic approaches are common: Convergent growth starts from the outside layer inward, whereas divergent growth begins at the central core. The former method allows for greater purity and branch control, whereas the latter method is favored for larger structures. The selection of a synthesis technique is governed by the required properties of the final product and the available reagents.

Inspired by the need for a less toxic, biocompatible aliphatic dendrimer for drug delivery, Ihre et al. have developed a divergent anhydride-coupling technique that requires no additional purification techniques beyond solvent extraction and precipitation. They prepared a monodisperse sixth-generation dendrimer in high yield. They also synthesized linear-dendritic hybrid polymers, in the shapes of fans, dumbbells, or crossed dumbbells starting from linear or cross-shaped poly(ethylene glycol)-based cores. Molecules produced by these techniques are currently being evaluated as potential catalysts and polymer therapeutics. — MSL

J. Am. Chem. Soc., in press.

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