Polyvinylferrocene-Based Amphiphilic Block Copolymers Featuring Functional Junction Points for Cross-Linked Micelles

Abstract

The synthesis of high-molecular-weight, welldefined poly(vinylferrocene)-block-poly(ethylene glycol) (PVFc-b-PEG) diblock copolymers (M n = 13 000−44 000 g mol −1 ; Đ = 1.29−1.34) with precisely one allyl group at the junction point is introduced. Allyl glycidyl ether (AGE) was used to end-functionalize PVFc, resulting in hydroxyl functional macroinitiators for the oxyanionic polymerization of ethylene oxide. The self-assembly behavior of the amphiphilic PVFc-b-PEG copolymers in water has been investigated in a detailed manner, using dynamic light scattering (DLS) and transmission electron microscopy (TEM). The redox activity of the PVFc block was confirmed by UV/vis spectroscopy, while cyclovoltammetry (CV) measurements were carried out to support the stability and full reversibility of the ferrocene/ferrocenium redox couple. Both formation and dissociation of the macromolecular self-assemblies in aqueous solution via oxidation and reduction of the PVFc segments were evidenced by TEM and DLS. The dye Nile Red was used as model compound to investigate the stabilization of a water-insoluble molecule in aqueous solution by the block copolymers via encapsulation inside micellar structures. Oxidation of the PVFc segments lead to instantaneous and quantitative release of the dye. Furthermore, incorporation of the allyl moiety at the block junction point was used to cross-link the shell of the compartments. By this strategy a stable incorporation of the dye was achieved while triggered release via oxidation led to quantitative liberation.

Multifunctional triazolylferrocenyl Janus dendron: Nanoparticle stabilizer, smart drug carrier and supramolecular nanoreactor

“…Redox‐responsive Fc‐containing macromolecules have recently gained considerable attention due to their potential in controllable delivery and release in physiological environments, where redox reactions are widely and constantly present . The reversible conversion between hydrophobic Fc group and hydrophilic ferrocenium by chemical and electrochemical reduction is a great advantage for the construction of reversible self‐assembly and disassembly systems, and thus afford Fc‐containing macromolecules as the optimal candidates for redox‐stimuli‐responsive drug carriers . Here, dendron 7 possesses not only the asymmetric and amphiphilic characters of Janus structures, but also the redox‐sensitive Fc moiety; thus it was speculated that it would self‐assemble into micelles used to load drugs for oxidation‐triggered release as shown in Figure .…”

“…The oxidation of the Fc moiety to cationic Fe III species is associated with an increase of the polarity and charge. This feature has been employed to modulate the self‐assembly or disassembly of Fc‐containing polymers . Here, the stimuli‐induced release of the payload was determined by monitoring the decrease of RhB UV–visible absorption intensity with time in the aqueous release medium after application of stimuli.…”

Light‐triggered stabilization of microgel aggregates

“…To overcome these limitations, new strategies for the preparation of long‐lasting aggregates have been introduced, including cross‐linking of the polymeric matrix . Nevertheless, the efficiency of these systems has not been clearly proven, and they frequently involve harsh conditions (eg, oxidizing agents and free radicals) that may impair functionality of many biomolecules . Other attempts to stabilize the structure of multimolecular hydrogel aggregates (also termed microgels) involved light as a cross‐linking agent, resulting in the destruction of the particulate structure and formation of a continuous film …”

“…12 Nevertheless, the efficiency of these systems has not been clearly proven, and they frequently involve harsh conditions (eg, oxidizing agents and free radicals) that may impair functionality of many biomolecules. 13,14 Other attempts to stabilize the structure of multimolecular hydrogel aggregates (also termed microgels) involved light as a cross-linking agent, resulting in the destruction of the particulate structure and formation of a continuous film. 15 Here, we present a straightforward, "one pot" synthetic scheme for the fabrication and stabilization of hydrogel aggregates.…”

New ROMP Synthesis of Ferrocenyl Dendronized Polymers

“…[1][2][3][4][5][6][7][8] Ferrocene (Fc)-containing macromolecules including metallopolymers and metallodendrimers are a continuing focus and standard in this area. [9][10][11][12] This broad interest is due to the rich Fc chemistry [13][14][15][16] and redox properties that, as for fullerenes, [17][18][19] lead to various architectures and functional applications such as molecular batteries, [20,21] emissive and photovoltaic materials, [22,23] sensors and molecular recognition, [24][25][26] nanolithography, [27,28] drug delivery vehicles, [29][30][31][32] hydrogels, [33][34][35] catalysts, [36][37][38] and stimuli-responsive materials. [39][40][41] The Fc-containing polymers belong to two major classes, namely, the main-chain Fc-containing polymers with the Fc unit as an integral part of polymer backbone, [1] and the side-chain Fc-containing polymers with Herein, we report a reliable synthetic pathway for the preparation of well-defined high molecular weight side-chain Fc-containing dendronized polymers via living and controlled ROMP reactions initiated by Grubbs' very ...…”