Hollow Helices as Folding Nanotubes with Tunable Cavity Size
EMSL Project ID
2433
Abstract
Two different classes of oligomers and polymers consisting of benzene rings linked by amide and ethynyl groups respectively are designed to fold into large helical structures. The backbones of these oligomers and polymers are rigidified by intramolecular hydrogen bonds. An oligomer with a backbone that is long enough folds back on itself, leading to left- and right-handed helices. Such a backbone-based helical programming leads to helices whose folded conformation is resilient toward structural variation of the side groups that determine the outside surface properties. The interior of a helix is featured either by amide O atoms, which leads to large hydrophilic cavities, or by aromatic H atoms, which makes the tubular cavities rather hydrophobic. The internal diameters of the helices are adjustable (8 E to 40 E and larger), which represent two versatile systems of unnatural folding nanotubes with adjustable interior cavities. Furthermore, one class of these unnatural foldamers have backbones that are helical as well as unsaturated, features that may endow unusual and useful physical and chemical properties. The design and synthesis of helices with superhydrophobic (fluorinated) or amphiphilic interior cavities will be tested. The resolution of enantiomers, induction of helical twist sense by chiral side chains and chiral solvents are being pursued. The photophysics, binding behavior, environment within the nanocavities, and nanofluidic properties of these folding nanotubes are being investigated by methods involving fluorescence, calorimetry, and computational studies. One powerful technique for characterize these oligomers is modern mass spectrometry such as electrospray mass spectrometry (ESI). We found it increasingly difficult to characterize larg oligomers as their structural complexity starts to reach the limit of techniques such as 1D and 2D NMR. The molecular weights of these large oligomers also is reaching the limit of standard mass spectral techniques. By taking advantage of the mass spectrometry facilities at PNNL, which represent one of the best in the world, the difficulty in characterizing the oligomers, and in the future polymers with high molecular weight and protein-like structural complexity, can be easily addressed. The most valuable information available from mass spectral measurements at PNNL will be the molecular weights of these large molecules, which provide a rapid means to the identification of the sythesized molecules. The mass spectral measurements are indispensable since the efficiency and detection range seen the mass spectral measurements is not matched any other methods. The resulting oligomers and polymers should lead to nanoporous materials that will find numerous applications in a number of areas, such as catalysis, separation, drug carriers, nanodevice (sensors, fluidic, etc.) design, nanoscaffolds for building larger structures, and design of other nanoporous materials.
Project Details
Project type
Exploratory Research
Start Date
2002-02-28
End Date
2005-03-01
Status
Closed
Released Data Link
Team
Principal Investigator