New Approaches to Cyclodextrin-Based Organic Nanotubes

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In this project, we propose to (a) develop new efficient approaches to processable cyclodextrin nanotubes (CyNT) and (b) characterizing transport of small molecules in CyNTs using advanced NMR methods. CyNTs will be synthesized in a template directed approach, including (a) synthesis of CD polyrotaxanes (b) crosslinking adjacent CDs through their hydroxyl groups, (c) cleavage of stopper groups, (d) removal of polymer template, and (e) purification. We shall synthesize both dimeric and polymeric CyNTs and overcome several known difficulties: (1) low molecular weights of CyNTs (2) low yields and tedious isolation of polyrotaxanes and CyNTs (3) limitation on α-CD. Polyrotaxanes will be synthesized with a new methodology in which polymer growth, threading of CDs and stoppering are carried out simultaneously. Better crosslinking reactions will be applied, like metathesis, click couplings of adjacent CDs. Polycondensation of endfunctionalized short CyNTs will lead to high molecular weight CyNTs. We will focus on γ-CyNTs, because they are yet unknown but highly desirable for inclusion and transport of drugs like steroids or taxol. Composition, structure, and size of rotaxanated intermediates and CyNTs will be characterized by diffusionordered NMR spectroscopy (DOSY). Translational and rotational dynamics of probe molecules in the CyNTs will be examined as functions of sample loading and temperature using solid-state and pulsed-field-gradient NMR techniques.