Cyclodextrins (CDs) and their chemically modified derivatives have been the subject of numerous investigations [1][2][3][4][5][6][7][8]. These compounds have found a large number of applications in many areas, since they have become available in high quantities, e.g. food chemistry as well as cosmetic and pharmaceutical industries. Furthermore, they can be used in organic chemistry or in polymer chemistry as well. Cyclodextrins are obtained by degradation of starch. They are cyclic oligosaccharides consisting of 6 (a), 7 (b), or 8 (g) glucopyranose units, which are joined together by a (1 ! 4)-linkage forming a torus-shaped ring structure. The primary hydroxy groups in 6-position are located at the narrow side of the torus, whereas the secondary glucopyranose OH-groups are located at the wider side of the torus (Fig. 1). Due to their polar hydrophilic outer shell and relatively hydrophobic cavity, they are able to build up host-guest complexes by inclusion of suitable hydrophobic molecules (Fig. 2). The formation of these complexes leads to significant changes of the solubility and reactivity of the guest molecules, but without any chemical modification. Thus, water insoluble molecules may become completely water soluble simply by mixing with an aqueous solutions of native CD or CD-derivatives, e.g. methylated or hydroxypropylated CD. Hydrogen bonds or hydrophobic interactions are responsible for the stability of the complexes. Based on this knowledge we were encouraged to investigate the behavior of CDcomplexes of various monomers, e.g. of methacrylates or methacrylamides. The formation of the complexes can be verified by FT-IR, 1 H NMR, or 2D-ROESY NMR spectroscopy. As an example, the X-ray structure of isobornyl acrylate (5a)/b-DMCD complex (b-DMCD: Heptakis (2,6-di-O-methyl b-cyclodextrin) show that the monomeric guest fits into the cavity of 2,6-dimethyl b-cyclodextrin (Fig. 3), whereby the double bonds are located on the narrow side of the conical shaped CD [9].
It turned out that the complexed monomers can be successfully polymerized via free radicals in water. Originally the interest was focused on standard guest monomers, which are represented in Table 1 according to Scheme 1. It was found that in nearly all cases the resulting polymer precipitates rapidly in high yields and the cyclodextrin slips off step by step from the growing chain and thus remains nearly quantitatively in the water phase. The unthreaded cyclodextrin is soluble in water and thus can be reused to entrap new monomer.