Cyclodextrin Dimers and Polymers

Since space is limited within the internal cavities of a-, (3-, and y-CDs, it was desirable to connect two and more CD rings to achieve some cooperativity in binding large guests. Two a-CD rings had been connected by one or two bridges at the primary rims [76], Two (3-CD had been connected, as well, via one or two bonds to a dimer by Breslow et al. [49,77-81], Recently, a heterodimer of a-CD and (3-CD was also synthesized [82], 

CD polymers can be synthesized (1) by radical polymerization of monofunctional CD monomers, (2) by polymer-analogous reaction of polymers with CDs, and (3) by partial crosslinking of CDs, as exemplified below. 

Crosslinking of a-CD with epichlorohydrin in aqueous solution under well controlled conditions furnished hyperbranched water-soluble a-CD polymers [96,97]. On the other hand, template directed crosslinking of a-CD, threaded on PEG, gave rise to linear CD polymers with two to three bridges between every two neighboring rings, or so-called molecular tubes, as shown in Fig. 2 [98-101], 

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