Web Release Date: January 10,
Size and Shape Variation of Polyphenylene Dendrimers through the Heterogeneous Hydrogenation of Embedded Triple Bonds
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Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany, and Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstrasse 12, D-53115 Bonn, Germany
Received September 6, 2007
Revised Manuscript Received November 4, 2007
Abstract:
Different generation polyphenylene dendrimers possessing eight diphenylacetylene units in the dendritic scaffold between the layers of the first and second generation have been synthesized by using a new p-phenylene ethynylene-functionalized tetraphenylcyclopentadienone branching unit. The heterogeneous hydrogenation of the embedded triple bonds in the final dendrimers was successfully performed via heterogeneous catalysis. Moreover a "softening" effect of the dendritic structure in consequence of the hydrogenation is observed, allowing for the first time the investigation of this effect upon size, shape, and intramolecular voids in the case of similar dendrimer pairs. Quartz microbalance studies revealed that upon hydrogenation the capacity in host uptake is decreased allowing the incorporation of a lower number of guest molecules compared to the parent materials.
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