Chemistry

Triggering Polymer Destruction

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Science  12 Dec 2003:
Vol. 302, Issue 5652, pp. 1863
DOI: 10.1126/science.302.5652.1863a

Dendrimeric polymers are synthesized in several reaction cycles that add monomer groups to a central core—hence they normally expand geometrically with each round of synthesis. Szalai et al. have created a small dendrimer that can be disassembled geometrically: a single chemical triggering event leads to two subsequent fragmentations in each subunit and completely reduces the polymer back to monomers. The dendrimers are built from 2,4-bis(hydroxymethyl)phenol units. The removal of a carbocation creates a phenoxide that then cleaves and liberates two alkoxide groups in the presence of a suitable nucleophile. They synthesized a small dendrimer with nitrophenoxy reporter groups and a single “trigger” group and show that a second-generation dendrimer can be disassembled in under a minute. If such a process can be extended to higher generation dendrimers, it could be used to release molecules, such as drugs, that have been trapped noncovalently within the spaces between the arms of the dendrimer vehicle. — PDS

J. Am. Chem. Soc. 10.1021/ja0386694 (2003).

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