Liao Peng

CO2‐Responsive Nanofibrous Membranes with Switchable Oil/Water Wettability

Responsive polymer interfacial materials are ideal candidates for controlling surface wetting behavior. Here we developed smart nanostructured electrospun polymer membranes which are capable of switching oil/water wettability using CO2 as the trigger. In particular, the combination of CO2 -responsiveness and porous nanostructure enables the as-prepared membranes to be used as a novel oil/water on-off switch. We anticipate that the promising versatility and simplicity of this system would not only open up a new way of surface wettability change regulation by gas, but also have obvious advantages in terms of highly controlled oil/water separation and CO2 applications.

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.

Facile and Efficient Fabrication of Photoresponsive Microgels via Thiol–Michael Addition

A photoresponsive microgel is designed by the combination of a noncovalent assembly strategy with a covalent cross-linking method. End-functionalized poly(ethylene glycol) with azobenzene [(PEG-(Azo)(2))] was mixed with acrylate-modified β-CD (β-CD-MAA) to form photoresponsive inclusion complex through host-guest interaction. The above photoresponsive complex was cross-linked by thiol-functionalized PEG (PEG-dithiol) via Michael addition click reaction. The photoreversibility of resulted microgel was studied by TEM, UV-Vis spectroscopy, and (1)H NMR measurements. The characterization results indicated that the reversible size changes of the microgel could be achieved by alternative UV-Vis irradiations with good repeatability.

Polymeric Nanocarriers Based on Cyclodextrins for Drug Delivery: Host–Guest Interaction as Stimuli Responsive Linker

Stimuli responsive polymers have been extensively studied as nanocarriers for drug delivery systems (DDSs), especially those based on supramolecular interactions. Cyclodextrin (CD) is one kind of widely applied host molecule, and the host-guest interactions between CD and different counterparts can respond to different stimuli and thus can be applied as responsive linkers for polymeric DDSs. In this review, the polymeric nanocarriers based on the host-guest interactions between CD and ferrocene, azobenzene, and benzimidazole as DDSs are summarized, with redox, light, and pH sensitivity, respectively. The mechanisms for the stimuli responsive ability of the linkers, the application of them for construction of DDSs with different polymer structures, and the controlled release behaviors have been focused. In addition, the outlook and challenge of these systems are discussed.

CO2-switchable drug release from magneto-polymeric nanohybrids

CO2-responsive well-defined core–shell–corona structure magnetic Fe3O4@SiO2-poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) nanocarriers have been developed as efficient drug delivery systems. The hybrid magnetic nanoparticles (MNPs) demonstrated a sandwich structure and highly super-paramagnetic biocompatibility properties as well as gas-responsive behavior. We found that the hydrodynamic radius (Rh) of the magnetic hybrid nanoparticles could be adjusted by alternate CO2/N2 treatment driving a switchable volume transition from contraction to expansion because of the CO2 responsiveness of PDMAEMA. The CO2-triggered protonation of the polymer shell gives rise to an obvious zeta potential change of the nanoparticles. Importantly, the CO2 induced reversible “on–off” transformation makes it possible to perform a dosage release of doxorubicin (DOX) in vitro in a time-controllable manner which is of great significance in controlled drug release. In the presence of CO2, the drug release rate is significantly accelerated, while low drug release could be achieved by removal of CO2 using N2. Moreover, the in vitro cytotoxicity test indicated that the CO2-responsive magnetic nanocarriers have good biocompatibility and could be safely used in living systems.

Electrochemical Redox Switchable Dispersion of Single-Walled Carbon Nanotubes in Water

We present a new, efficient approach to achieve superior dispersibility of single-walled carbon nanotubes (SWNTs) in water by integrating reversible host-guest interaction and π-π stacking. In this approach, β-cyclodextrin (β-CD) was first modified with a pyrene group to be adsorbed onto the wall of pristine SWNTs via π-π stacking, followed by further functionalization with ferrocene (Fc)-terminated water-soluble poly(ethylene glycol) (PEG) through supramolecular host-guest interaction between β-CD and Fc. Upon alternate electrochemical oxidative/reductive stimuli, the reversible host-guest pair enabled the PEG-Fc@Py-CD@SWNTs to exhibit switchable conversion between dispersion and aggregation states. Electric field controllable PEG-Fc@Py-CD@SWNTs with good reversibility and intact nanotube structure may find potential applications in selective screening of SWNTs, biosensors, and targeted drug delivery.

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.

Synthesis of Air‐Stable Cyclopentadienyl Fe(CO)2 (Fp) Polymers by a Host–Guest Interaction of Cyclodextrin with Air‐Sensitive Fp Pendant Groups

Host-guest chemistry is used to address the challenge of the synthesis of air-stable polymers containing air-sensitive metal complexes. The complexation of the CpFe(CO)2 (Fp) pendent group with cyclodextrin (CD) molecules created air-stable poly(Fp-methylstyrene) P(CD/FpMSt). This CD complexation resulted in dimerization of the adjacent Fp groups, which was characterized by NMR, FTIR, and cyclic voltammetry (CV) analyses. P(CD/FpMSt) was soluble in DMSO and remained stable even the solution was exposed to air for months. The host-guest chemistry accounted for the improved stability, because the Fp groups decomposed upon removal of the CD molecules using competing guest molecules. The CD-complexed polymer showed light-trigged properties, including CO release and antimicrobial activity. Host-guest chemistry of air-sensitive organometallic complexes is therefore a promising technique that can be used to broaden the scope of metal-containing polymers (MCPs) with processable novel functions.