Investigating some Physical Properties of Functionalised PAMAM Dendrimers

Department of Physics, University of Durham, South Road, Durham, DH1 3LE, England.
tel: 0191 3742577. FAX: 0191 3743848. e-mail: G.H.Cross@Durham.ac.uk

As a new class of materials, dendrimers or "starburst" polymers have generated great interest throughout the scientific community. Despite synthetic difficulties 1, a wide range of these new materials have been produced and characterised 2, 3, 4. However, the study of their properties is still in its infancy (relative to classical polymers) and there remains large gaps in our knowledge which must be filled if the potential uses of these new materials are to be realised. Dendrimers are highly branched structures produced by either divergent or convergent synthetic methodologies 5 which allow the formation of monodispersed nanoparticles of controlled dimensions and specific surface functionalisation.

The work reported here involves the surface functionalisation of the terminal amino groups of PAMAM (polyamidoamine) dendrimers with aromatic moieties. We intend to investigate some physical properties (fluorescence spectral characteristics, non-linear optical responses) of various generations of these functionalised dendrimers and observe any differences in behaviour as progression is made from microscopic (lower generations) to mesoscopic (higher generation) morphology. It is envisaged that steric crowding at higher generations may lead to the onset of collective effects, especially as aromatic groups present the possibility of p orbital overlap 6. Of the chemistry investigated, the two reactions shown below were selected for further study and a series of several generations of functionalised PAMAM dendrimers were prepared.

The fluorescence spectra of different generations of compound (I) are presently being investigated. EFISH measurements of PAMAM dendrimers functionalised with the polar aromatic group -CH2C6H4NO2 (Compounds (II)) are being carried out and may reveal information about the changing dendrimer morphology between lower and higher generations. The results will be discussed.

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