Polymers with Sugar Buckets - The Attachment of Cyclodextrins onto Polymer Chains

This Review summarizes the structures obtained when marrying synthetic polymers of varying architectures with cyclodextrins. Polymers with cyclodextrin pendant groups were obtained by directly polymerizing cyclodextrin-based monomers or by postmodification of reactive polymers with cyclodextrins. Star polymers with cyclodextrin as the core with up to 21 arms were usually obtained by using modified cyclodextrins as initiator or controlling agent. Limited reports are available on the synthesis of star polymers by arm-first techniques, which all employed azide-functionalized cyclodextrin and 'click' chemistry to attach seven polymer arms to the cyclodextrin core. Polymer chains with one or two cyclodextrin terminal units were reported as well as star polymers carrying a cyclodextrin molecule at the end of each arm. Cyclodextrin polymers were obtained using different polymerization techniques ranging from atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, nitroxide-mediated polymerization, free radical polymerization to (ionic) ring-opening polymerization, and polycondensation. Cyclodextrin polymers touch all areas of polymer science from gene delivery, self-assembled structures, drug carriers, molecular sensors, hydrogels, and liquid crystalline polymers. This Review attempts to focus on the range of work conducted with polymers and cyclodextrins and highlights some of the key areas where these macromolecules have been applied.