Monodispersed dendritic polyesters with removable chain ends: A versatile approach to globular macromolecules with chemically reversible polarities

Craig J. Hawker*, Jean Frechet

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

118 Scopus citations

Abstract

A versatile approach to dendritic macro-molecules with aromatic polyester inner structure and a readily modified hydrophobic/hydrophilic 'surface' is described. The polyester fragments are prepared by a convergent growth process involving 3,5-bis(benzyloxy)benzoic acid as the 'surface' or chain-ending moiety and trichloroethyl 3,5-dihydroxybenzoate as the monomer unit. The key esterification step is accomplished in high yield using dicyclohexylcarbodiimide and 4-dimethylaminopyridinium toluene-p-sulfonate as condensing agents. The coupling step is followed by activation of the new focal point by removal of the trichloroethyl ester group with zinc-acetic acid. Repetition of this two-step process leads to large dendritic fragments that may be coupled to a polyfunctional core to complete the dendritic macromolecule. The chemistry chosen for this synthesis allows for subsequent selective removal of the numerous benzyl ether chain ends by hydrogenolysis to afford a dendritic macromolecule with phenolic chain ends. Further modification of the chain ends is readily accomplished in processes that effectively transform the initially hydrophobic dendritic molecule into one that is both hydrophilic and water-soluble. These transformations of the 'surface' functionalities are also accompanied by drastic changes in glass transition behaviour.

Original languageEnglish (US)
Pages (from-to)2459-2469
Number of pages11
JournalJournal of the Chemical Society, Perkin Transactions 1
Issue number19
StatePublished - Dec 1 1992

ASJC Scopus subject areas

  • Chemistry(all)

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