Breathing Pores on Command: Redox‐Responsive Spongy Membranes from Poly(ferrocenylsilane)s

Zhang, Kaihuan; Feng, Xueling; Sui, Xiaofeng; Hempenius, Mark A.; Vancso, Gyula J.

doi:10.1002/anie.201408010

Cited by 95 publications

(76 citation statements)

References 36 publications

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“…However, the network reswelled and regained its elasticity upon subsequent reduction and reestablishment of charge balance. 147 The PFS-VImTf 2 N/PAA membrane displayed redox responsive behaviour, which enabled reversible switching between open and closed porous structures with associated changes in permeability (Fig. 143 The redox state, and hence swelling and mechanical properties of the PFS, could be reversibly tuned.…”

Section: Redox-active Gelsmentioning

confidence: 99%

Polyferrocenylsilanes: synthesis, properties, and applications

et al. 2016

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This in-depth review covers progress in the area of polyferrocenylsilanes (PFS), a well-established, readily accessible class of main chain organosilicon metallopolymer consisting of alternating ferrocene and organosilane units. Soluble, high molar mass samples of these materials were first prepared in the early 1990s by ring-opening polymerisation (ROP) of silicon-bridged [1]ferrocenophanes (sila[1]ferrocenophanes). Thermal, transition metal-catalysed, and also two different living anionic ROP methodologies have been developed: the latter permit access to controlled polymer architectures, such as monodisperse PFS homopolymers and block copolymers. Depending on the substituents, PFS homopolymers can be amorphous or crystalline, and soluble in organic solvents or aqueous media. PFS materials have attracted widespread attention as high refractive index materials, electroactuated redox-active gels, fibres, films, and nanoporous membranes, as precursors to nanostructured magnetic ceramics, and as etch resists to plasmas and other radiation. PFS block copolymers form phase-separated iron-rich, redox-active and preceramic nanodomains in the solid state with applications in nanolithography, nanotemplating, and nanocatalysis. In selective solvents functional micelles with core-shell structures are formed. Block copolymers with a crystallisable PFS core-forming block were the first to be found to undergo "living crystallisation-driven self-assembly" in solution, a controlled method of assembling block copolymers into 1D or 2D structures that resembles a living covalent polymerisation, but on a longer length scale of 10 nm-10 μm.

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Section: Redox-active Gelsmentioning

confidence: 99%

Polyferrocenylsilanes: synthesis, properties, and applications

et al. 2016

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“…Complete electrochemical oxidation of PFSs is achieved at redox potentials below 1 V. 27,30,31 PFSs can be incorporated into polymer architectures by copolymerization 32,33 and can form dual-responsive systems via side-group modification, 34 opening possibilities for the fabrication of complex material structures such as hydrogels 34 or porous membranes. 35 An interesting alternative method which gives a significant change in surface energy has been reported for a low-density self-assembled monolayer (SAM) of (16-mercapto)-hexadecanoic acid on gold substrates using a molecular backbiting transition. This transition was, however, driven by high-voltage electric fields.…”

Section: ■ Introductionmentioning

confidence: 99%

Redox-Induced Backbiting of Surface-Tethered Alkylsulfonate Amphiphiles: Reversible Switching of Surface Wettability and Adherence

et al. 2015

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The synthesis and characterization of electrode-supported poly(ferrocenylsilane) (PFS) films bearing iodopropyl (PFS-I) and undecanesulfonate (PFS-SO3(-)) surface moieties are presented. The redox responsiveness of these PFS films allows for controlled and repeatable switching of the surface energy of the PFS-I and PFS-SO3(-) layers under electrochemical control. Static water/surface contact angle measurements showed a change in contact angle values for PFS-I from 80° (reduced state) to 70° (oxidized state) over repeated cycles. However, an opposite change in wettability was observed for PFS-SO3(-), where the values observed varied from 59° (reduced state) to 77° (oxidized state). Nanoscale adherence was assessed with colloid probe AFM. The adhesive forces between these surfaces and a polystyrene (PS) colloid probe in water alternated between 130 nN (reduced state) and 30 nN (oxidized state) for PFS-I layers and between 75 nN (reduced) and 180 nN (oxidized) for the PFS-SO3(-) films. The reversed response of PFS-I films to oxidation compared to that of PFS-SO3(-), in both contact angles and adhesive forces, suggests a different underlying mechanism for switching. As PFS-I is tuned from the reduced to the oxidized state, positively charged ferrocenium (Fc(+)) centers that formed in the film increase its wettability and reduce its adherence to the hydrophobic colloid probe. For PFS-SO3(-) in the reduced state, the exposed alkanesulfonate moieties increase the hydrophilicity of the surface. When oxidized, the Fc(+) units attract the negatively charged sulfonate groups, which results in a bending of the sulfonate groups toward the PFS surface, exposing the undecyl spacer. This alteration of the surface chemistry reduces the surface energy and increases the adherence between the bent alkyl chains and the hydrophobic PS colloid in water. The attraction of the charged sulfonate group to Fc(+) is in competition with the counterions present in the electrolyte solution. Therefore, the backbiting of the chain can be achieved only in electrolytes where the affinity of Fc(+) for the ions is lower than for the sulfonate group, in agreement with the Hofmeister series.

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“…146 The PFS-VImTf2N/PAA membrane displayed redox responsive behaviour, which enabled reversible switching between open and closed porous structures with associated changes in permeability ( Figure 12). The authors noted that such a system could have uses in selective filtration, the preparation of enzyme-entrapped membranes for bio-sensing, controlled loading and release, and catalysis in microfluidic reactors.…”

Section: Redox-active Gelsmentioning

confidence: 99%