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

Abstract

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.

Hydroxyl versus permethylated glycopolymers as gene carriers

“…In a recently published study [17], two complex styrenic structures, derived from the hydroxylated and permethylated forms of the cyclic oligosaccharide b-cyclodextrin (b-CD), were chosen as the neutral co-monomer entities [18][19][20][21][22]. Post polymerization, the copolymers showed significantly improved cytocompatibility and transfection efficiency in vitro compared to the EPA homopolymer and the positive polyethyleneimine (PEI) control, especially in the case of the copolymers derived from the permethylated form of b-CD.…”

Building nanostructures using RAFT polymerization

“…A number of compounds have been employed successfully as cores for RAFT-star-syntheses, for example, cyclodextrins, 302,304 aromatic groups, 305 dendrimers, [306][307][308] hyperbranched polymers [309][310][311] or metal complexes. 312 RAFT functionality can be attached to the core via either the R or Z groups.…”

Thermoresponsive Supramolecular Dendronized Polymers

“…The host polymer with the b-cyclodextrin (b-CD) moiety appended was obtained by directly polymerizing the CD-based monomer, similar to literature methods (Scheme 2). [41] Here, mono-6-deoxy-6-amino-b-CD (3) was treated with active ester 4 in a mixed solvent of N,N-dimethylformamide (DMF) and methanol to form the macromonomer 5, which was subjected to free radical polymerization in highly concentrated DMF solutions and afforded linear CD polymer poly(5) with a well-defined structure. The high CD mono-mer concentration in polymerization media is a prerequisite for obtaining a high-molar-mass polymer.…”