Redox‐Switchable Supramolecular Graft Polymer Formation via Ferrocene–Cyclodextrin Assembly

Abstract

The redox switchable formation of very well-defined supramolecular graft polymers in aqueous solution driven by host-guest interactions between ferrocene (Fc) and cyclodextrin (CD) is presented. The Fc-containing acrylic backbone copolymer (PDMA-stat-Fc) is prepared via reversible addition-fragmentation chain transfer (RAFT) copolymerization of N,N-dimethyl-acrylamide (DMA) and the novel monomer N-(ferrocenoylmethyl)acrylamide (NFMA). Via the RAFT process, copolymers containing variable Fc ratios (5-10 mol%) are prepared, affording polymers of molecular masses of close to 11,000 g mol(-1) and molar mass dispersities (Đ) of 1.2. The β-cyclodextrin (β-CD) containing building block is synthesized via RAFT-polymerization, too, in order to afford a polymer with well-defined molecular mass and low dispersity (Mn = 10 300 g mol(-1) , Đ = 1.1), employing a propargyl-functionalized chain transfer agent for the polymerization of N,N-diethylacrylamide (DEA). The polymerization product is subsequently terminated with β-CD via the regiospecific copper (I)-catalyzed 1,3-cycloaddition (PDEA-βCD). Host-guest interactions between Fc and CD lead to the formation of supramolecular graft-polymers, verified via nuclear Overhauser enhancement spectroscopy (NOESY). Importantly, their redox-responsive character is clearly confirmed via cyclic voltammetry (CV). The self-assembly of the statistical Fc-containing lateral polymer chain in aqueous solution leads to mono- and multi-core micelle-aggregates evidenced via TEM. Only diffused cloud-like, non-spherical nanostructures are observed after addition of PDEA-βCD (TEM).

Supramolecular control over thermoresponsive polymers

“…In analogy to end-functionalized host/guest polymers, incorporation of supramolecular motifs across the polymer backbone render supramolecular graft copolymers with tunable micellization behavior [73][74][75]. In this context, a very recent report by Huang et al describes the reversible switching between micellar and vesicular structures by the application of temperature or light stimuli [76].…”

Dynamic Macromolecular Material Design—The Versatility of Cyclodextrin‐Based Host–Guest Chemistry

“…Furthermore, Ritter and co-workers [97] as well as Yuan and co-workers [98] described redox-responsive brush polymers that are capable of switching between al inear and ab rush state on oxidation or reduction of the ferrocene moieties,respectively.F rey and co-workers described brush formation with adamantyl-functionalized PEG-b-HPG together with CD-functionalized PHPMA. [99] Here,t he supramolecular brush polymer formation was studied through determination of the association constant.…”

Redox-responsive polymeric membranes via supermolecular host–guest interactions

“…It was known that Fc and β-CD could form inclusion complex due to the interaction between Fc and β-CD [36,48,49]. To figure out the interaction between PES-PEG-Fc and PES-PEG-β-CD, 2D NMR (NOESY) spectra test was performed to evidence the formation and dissociation of the inclusion complex between the Fc moieties on PES-PEG-Fc and the β-CD moieties on PES-PEG-β-CD.…”