Anchao Feng

Redox-switchable supramolecular polymers for responsive self-healing nanofibers in water

Self-healing nanomaterials that respond to new stimuli sources are attractive. In particular, redox potential is one of the most universal and convenient stimuli in nature. Here we report utilization of ferrocene- and cyclodextrin-terminated monomers to form water-soluble AA-BB-type supramolecular polymers on the basis of host–guest interactions of ferrocene (Fc) and cyclodextrin (CD). These noncovalent polymers can further hierarchically assemble into one-dimensional supramolecular nanofiber architectures. The electrochemical-responsive Fc–CD host–guest connections endow these nanofibers with unique self-degradable and -healable features under redox potential control. Moreover, different redox conditions can exactly regulate the self-repairable rates of these nanostructures. It is anticipated that this supramolecular polymer model would open up a way for redox-tunable one-dimensional nanomaterials.

Voltage-responsive micelles based on the assembly of two biocompatible homopolymers

Voltage stimulus is considered as a clean and simple method in the field of stimuli-responsive polymer systems, in which the system based on β-cyclodextrin (β-CD) and ferrocene (Fc) has attracted considerable attention. Herein, we report voltage-responsive micelles based on the assembly of two biocompatible homopolymers, namely, the poly(ethylene glycol) homopolymer modified with β-CD (PEG–β-CD) and the poly(L-lactide) homopolymer modified with Fc (PLLA–Fc). Through host–guest interactions between β-CD and Fc, the two homopolymers connect together, forming a non-covalent supramolecular block copolymer PLLA–Fc/PEG–β-CD. PLLA–Fc/PEG–β-CD can further self-assemble to form stable micelles in aqueous solution. Through electrochemical control, a reversible assembly–disassembly transition of this micellar system was realized. Voltage-controlled drug release based on this system was also conducted successfully.

Electrochemical redox responsive supramolecular self-healing hydrogels based on host–guest interaction

A supramolecular hydrogel was prepared through the host–guest interaction between β-cyclodextrin (β-CD) and ferrocene (Fc) with two polymers as pendant groups. Reversible gel–sol transition was observed with the alternative stimuli of a positive potential (or an oxidant) and a negative potential (or a reductant). The hydrogel not only had good self-healing ability due to the dynamic host–guest interaction, but also was prepared under mild conditions and could respond to moderate electrochemical stimuli. Good biocompatibility endowed the hydrogel with potential practical and real-life applications, especially in tissue engineering and drug release field.

Electrochemically-responsive magnetic nanoparticles for reversible protein adsorption

Electrochemical stimulus is a clean and simple choice of stimulating source in the field of stimuli-responsive materials. Herein, we report an electrochemically-responsive hybrid assembly of magnetic nanoparticles (Fe3O4@SiO2-PGMA-CD) and polyethylene glycol-Fc (PEG-Fc) based on the host-guest interaction between β-cyclodextrin and ferrocene groups. Through electrochemical control, the hydrophilic polymer chains can be reversibly linked to or dropped off from the surface of the magnetic nanoparticles. Thus, the hydrophobic property of the surface together with the protein adsorption ability of the magnetic nanoparticles can be conveniently adjusted by voltages applied. A reversible protein adsorption/release transition from this novel hybrid material has been realized, demonstrated by the bovine serum albumin adsorption experiment. Therefore, an elegant material is introduced to achieve electrochemically-controlled reversible magnetic separation of proteins.

Breathing catalyst-supports: CO2 adjustable and magnetic recyclable “smart” hybrid nanoparticles

A facile route for fabricating CO2 gas stimulated, magnetically recyclable hybrid nanoparticle is designed and illustrated through introducing a CO2 sensitive polymeric matrix and gold nanoparticles (AuNPs) onto the surface of magnetic Fe3O4@SiO2 nanospheres. The accessibility of the AuNPs to the reaction substrates can be tuned following swollen or collapsed of CO2 sensitive shell, which may leads to an increase or decrease of catalytic activity. Therefore, the obtained hybrid system offers a novel strategy to adjust and control the catalytic activity through mild stimulation of CO2/N2, where the magnetic core assures a magnetically recyclable catalysis.