Cyclodextrins in polymer synthesis: Free radical polymerization of methylated beta-cyclodextrin complexes of methyl methacrylate and styrene, controlled by dodecanethiol as the chain-transfer agent in aqueous medium

Methylated beta -cyclodextrin (me-beta -CD) was used to complex the hydroph obic monomers methyl methacrylate (1) or styrene (2) yielding the water-sol uble 1:1-host/guest complexes methyl methacrylate/me-beta -CD (1a) and styr ene/me-beta -CD (2a), respectively. In addition, the hydrophobic chain-tran sfer agent dodecanethiol (3) was complexed by two equivalents of me-beta -C D yielding the water-soluble dodecanethiol/me-beta -CD (3a). The included m onomers were polymerized in water by a free-radical mechanism in the presen ce of 3a as the chain-transfer agent. The chain-transfer constants were det ermined. In order to evaluate these results, the chain-transfer constants o f 3 were also determined in the case of the corresponding uncomplexed monom ers 1 and 2 in organic solution. It was found that the chain-transfer const ants of 1a and 2a (Cs-1a = 0.5 +/- 0.2, Cs-2a = 2.2 +/- 0.3) are significan tly tower compared with the values obtained from the polymerizations of the corresponding uncomplexed monomers 1 and 2 in organic solution (Cs-1 = 3.1 +/- 0.3, Cs-2 = 3.4 +/- 0.3).