Conformational studies of dendritic macromolecules by solid state NMR and AFM
- Stanford Univ., CA (United States)
- Mitsubishi Chemical America, Inc., San Jose, CA (United States)
The solid-state shape, size, and intermolecular packing of dendritic macromolecules were determined by a combination of site-specific stable-isotope labeling, rotational-echo double resonance (REDOR) solid-state NMR, atomic force microscopy (AFM), and distance-constrained molecular dynamics simulations. For benzyl ether dendrimers of generations one through five, based on 3,5-dihydroxybenzyl alcohol as the monomeric repeat unit, REDOR experiments measured dipolar couplings between {sup 13}C atoms located at the chain ends and an {sup 19}F label placed near the core of the structure. Intramolecular {sup 13}C-{sup 19}F coupling was distinguished from intermolecular coupling by dilution with unlabeled dendrimer. The NMR-determined intramolecular distances were compared to film thickness measurements by AFM for monolayer films of unlabeled dendrimers on graphite. The NMR-measured intra- and intermolecular distances for the fifth-generation dendrimer were used as constraints on energy-minimized molecular dynamics simulations, which resulted in visualizations of the dendrimer packing. The shape of the fifth-generation dendrimer was non-spherical with a completely encapsulated core and overall dimensions of 31{times}37{times}41 {Angstrom}.
- OSTI ID:
- 602863
- Report Number(s):
- CONF-961108--
- Country of Publication:
- United States
- Language:
- English
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