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The arm components of mikto-arm star polymers were quantitatively analyzed with a novel fluorescence strategy.

A versatile approach to the synthesis of migration-resistant poly(vinyl chloride) (PVC) additives is described and a preliminary assessment of their properties is presented. The process involves th...

Peptide-polymer conjugates represent a promising class of compounds that can be used to overcome some of the limitations associated with peptides intended for therapeutic and diagnostic applications. The efficient generation of well-defined peptide/protein-polymer conjugates can promote the development of the design and synthesis of functional drugs and gene delivery platforms. In this research, a sequence defined cell penetrating peptide (i.e., Transportan 10 (TP 10))-based chain transfer agent (TP-CTA) was designed and synthesized in an automated peptide synthesizer. Thereafter, amphiphilic block copolymers poly[oligo(ethylene glycol) methyl ether acrylate]

Switchable reversible addition–fragmentation chain-transfer (RAFT) agents, so-called because they can be reversibly switched by an acid/base stimulus to offer very good control over polymerization of both “more-activated” monomers (MAMs) and “less-activated” monomers (LAMs), provide a route to prepare well-defined polyMAM-block-polyLAM copolymers. This paper presents 1H NMR studies in determining the effect of the type and amount of acid on the efficiency of the protonation of a switchable RAFT agent. Acid type and concentration have a marked effect on the degree of control over switchable RAFT polymerization. Best control was achieved with a stoichiometric amount of the strongest acid investigated, trifluoromethanesulfonic acid. In addition, we describe a facile synthesis of the well-defined CO2-responsive gradient copolymers poly(benzyl methacrylate)-block-(poly(N,N-diethylaminoethyl methacrylate)-gradient-poly(N-vinylpyrrolidone))-block-poly(N-vinylpyrrolidone) (PBzMA-b-P(DEAEMA-grad-NVP)-b-PNVP) through switchable RAFT polymerization. The amphiphilic gradient copolymers can self-assemble to form various multicompartment micelles in selective solvents, and the assembled micelles widely possess patchy, noncontinuous subdomains around the inner micelle cores. Through CO2 stimulation, their inhomogeneous nature will endow the gradient copolymers with some different stimuli-responsive factors from those of block copolymers, which emerged with obviously heterogeneous and compartmentalized shell nanodomains. Furthermore, this gradient strategy may offer a new way to design and realize precise morphological manipulation.

Dual thermo- and pH-responsive star polymers with tunable upper critical solution temperatures (UCST) were synthesized by an “arm-first” RAFT polymerization approach. Crosslinking took place in a single step involving polymerization of 3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate (DMAPS) mediated by a macroRAFT agent containing carboxylic end-group and in the presence of crosslinker N,N-methylenebis(acrylamide) (MBA). Varied-temperature turbidity analysis, dynamic light scattering (DLS) and rheology analysis revealed that the star-shaped PDMAPS had a smaller hydrodynamic volume while retaining fast response properties, compared with linearly-shaped PDMAPS. Meanwhile, zeta-potential was used to determine that the range of UCST regulated by pH was greatly expanded and proportional to the number of end-groups that could be generally manipulated through RAFT polymerization. By changing the pH values from 3 to 10, the adjustable UCST range of the star polymer solution can reach over 36 °C. These results demonstrate that the topological structure and end-group effect are able to manipulate the phase transition behavior of polyzwitterions. These materials offer great potential as additives or drug delivery vehicles in biomedical applications.

An enzyme degassing method for oxygen-intolerant polymerizations was implemented in a commercially available automated parallel synthesizer and tested for reversible addition-fragmentation chain transfer (RAFT) polymerizations performed in open vessels. For this purpose, a recently reported methodology that employs the enzyme glucose oxidase (GOx) to deplete oxygen in reaction media was utilized. The effectiveness of this approach to perform unattended parallel polymerization reactions in open vessels was demonstrated by comparing experimental results to those obtained under similar experimental conditions but utilizing the common degassing method of sparging N

Poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA) is a promising drug platform as it is non-immunogenic, biocompatible and hydrophilic polymer. It is the first copolymer-drug conjugates to be evaluated in clinical trials. However, it is challenging to obtain well-controlled PHPMA with high conversions via either ATRP or RAFT polymerization in most organic solvents. In this study, we systematically investigate the polymerization of HPMA via RAFT in various solvents using 4-cyano-4-(((ethylthio)thioxomethyl)thio)pentanoic acid as a chain transfer agent. Kinetic experiments demonstrated that the retardation was alleviated in aprotic solvents resulting in low conversions and poor controllability of the polymerization. Variable temperature analyses and molecular dynamic simulation proved the low conversion and poor control of PHPMA was attributed to the hydrogen bonding of the polymeric system and the theoretical results are consistent with our experimental observations.

An alkyl halide containing monomer, 2-chloroethyl methacrylate (CEMA) was synthesized via the chorination of 2-hydroethyl methacryalte and polymerized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The kinetics of the controlled/living radical polyemrization (CRP) was systematically investigated. The chain end livingness of poly(2-chloroethyl methacrylate) (PCEMA) was confirmed by the chain extension with methyl methacrylate (MMA) under RAFT polymerization conditions. PCEMA with dangling alkyl chloride groups was directly azidated through a nucleophilic substitution with sodium azide, affording a polymer with an azido group at each repeating unit. The resulting polymer was readily available for post-polymerization modifications by various click reactions. These strategies may open new perspectives toward more effective and milder conditions for azide involving reactions.

Well-defined nonmigrating polymeric plasticizers, poly(vinyl chloride)-block-polycaprolactone (PVC-b-PCL), were synthesized by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP) with 2-hydroxyethyl 2-(ethoxycarbonothioylthio)propanoate (HECP) as RAFT agent and incipient initiator for ROP of e-caprolactone (CL, oxepan-2-one). Kinetic experiments demonstrated that HECP provided good control in RAFT polymerization of vinyl chloride (VC) with dispersity (Đ) ∼ 1.2 for 3400 < Mn < 11000. Chain extension experiments with VC and vinyl acetate proved the high end-group fidelity of the macroRAFT agent formed. The hydroxy end-group of the PVC macroRAFT agent allowed its use as a ROP initiator in forming a series of PVC-b-PCL with different PCL block lengths by RAFT-T-ROP. Characterization by wide-angle X-ray diffraction (WAXD), polarized light microscopy (PLM), and differential scanning calorimetry (DSC) indicates that there is enhanced chain enta...

This paper presents a facile synthesis of poly(methacrylic acid)-block-poly(N-vinylpyrrolidone) (PMAA-b-PNVP) block copolymer utilizing a stimuli responsive RAFT agent that can be switched to offer good control over the polymerisation of MAMs and LAMs. Commercially available acid/base switchable RAFT agents, e.g., 2-cyanopropan-2-yl N-methyl-N-(pyridine-4-yl)carbanodithioate, were used and the block copolymer PMAA-b-PNVP was obtained after the hydrolysis of the corresponding well-defined, low dispersity poly(t-butyl methacrylate)-block-poly(N-vinylpyrrolidone) (P(t-BMA)-b-PNVP). This block copolymer has an advantage over its random copolymer counterpart as it can self-assemble to form micelles under acidic conditions.

Examples of successful therapies using macromolecular prodrugs to which the drug is linked via covalent bonds have been reported; however, there are safety concerns which render them disfavourable for clinical applications. Therefore, it is essential to reassess this class of drugs by designing compounds that combine covalent linking with reducible linkers. Herein, the hydrophobic drug paclitaxel was modified into a polymerizable monomer and subsequently copolymerized with pH-sensitive monomers and redox-sensitive disulfide-based cyclic monomers. The resulting diblock copolymer can self-assemble into vesicles incorporating the hydrophobic drug PTX into the vesicle walls. On decreasing the pH value, the size of the vesicular drug container varied with the change in the hydrophobicity–hydrophilicity balance. Treatment with reducing agents mediated the disassembly of the aggregates facilitating the release of the drug moiety. Furthermore, in vitro cell experiments showed that the nanoparticles exhibited cytotoxicity, indicating that they have potential as a drug delivery system for anti-cancer treatments.

Inspired by nature, supramolecular nanoparticles based on complementary nucleobase interactions have aroused wide interest. In our study, two kinds of fluorophores were conjugated at the end of nucleobase containing homopolymers, which can be used to confirm the binding state and calculate the binding constants among different nucleobase pairs. Furthermore, we describe a facile synthesis of nucleobase-functionalized amphiphilic polymers with rigid and flexible backbones using RAFT polymerization. Spindle-like or telophase-like supramolecular self-assemblies were formed by different components of such synthetic amphiphilic polymers.

Miktoarm star (MAS) polymers are polymers with a number of distinct arms connected to a central core. Owing to their exclusive structure, MAS polymers have been extensively studied in recent years. To exploit their biomedical applications the combination of nucleic acids, peptides and saccharides are desired. In this study, RAFT polymerization of three monomers with markedly different properties, N,N-dimethylaminoethyl methacrylate (DMAEMA, cationic), n-butyl methacrylate (BMA, hydrophobic) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA, hydrophilic) was conducted using an RGD peptide based RAFT agent as a chain transfer agent (RGD-CTA). With a disulphide dimethacrylate (DSDMA) redox-cleavable cross-linker, the above linear polymers were combined via an “arm-first” technique to access MAS polymers containing peptide arms. These MAS polymers showed excellent biocompatibility, cell staining performance and rapid redox responsiveness. The novel MAS polymers have potential as a prospective platform for intracellular drug/gene delivery for cancer therapy.

Precise polymer architecture and self-assembled morphological control are attractive due to their promising applications, such as drug delivery, biosensors, tissue engineering and "smart" optical systems. Herein, starting from the same hydrophilic units poly(ethylene glycol) (PEG), using CO

This study aimed to modify an electrospun regenerated cellulose (RC) nanofiber membrane by surface grafting 2-(dimethylamino) ethyl methacrylate (DMAEMA) as a monomer via atom transfer radical polymerization (ATRP), as well as investigate the effects of ATRP conditions (i.e., initiation and polymerization) on enzyme immobilization. Various characterizations including XPS, FTIR spectra, and SEM images of nanofiber membranes before and after monomer grafting verified that poly (DMAEMA) chains/brushes were successfully grafted onto the RC nanofiber membrane. The effect of different ATRP conditions on laccase immobilization was investigated, and the results indicated that the optimal initiation and monomer grafting times were 1 and 2 h, respectively. The highest immobilization amount was obtained from the RC-Br-1h-poly (DMAEMA)-2h membrane (95.04 &plusmn, 4.35 mg), which increased by approximately 3.3 times compared to the initial RC membrane (28.57 &plusmn, 3.95 mg). All the results suggested that the optimization of initiation and polymerization conditions is a key factor that affects the enzyme immobilization amount, and the surface modification of the RC membrane by ATRP is a promising approach to develop an advanced enzyme carrier with a high enzyme loading capacity.

Molecular recognition plays an important role in biological systems. Exploiting the complementary base-pairing observed between nucleotides (in DNA and RNA) to build discrete multicomponent composite micelles would be of high value. Herein, we describe the synthesis of short chain block copolymers functionalized with the nucleobase adenine (A) or thymine (T). The copolymers self-assemble in a phosphate buffered aqueous solution and base-pairing is observed between the nucleobase end-functionalized block copolymer and the free nucleobase despite the highly competitive aqueous environment. This phenomenon is only observed when the nucleobase is attached to the hydrophilic end of the copolymer. Exposure to elevated temperatures destroys the hydrogen bonding (H-bonding) between the nucleobase end-functionalized block copolymer and the complementary nucleobase, thus releasing A or T from the micelle. The molecular recognition properties exhibited by these structures have the potential to build higher ordered structures and furnish nucleobase or DNA containing nanomaterials.

A feasibility study for the synthesis of well-defined miktoarm star polymers containing peptide arms in an automated parallel synthesizer is reported. A series of linear homo- and block (co–)polymers were prepared in the presence of commercial or peptide-functionalized reversible addition-fragmentation chain transfer (RAFT) agents. Thereafter, miktoarm star polymers were obtained by cross-linking different combinations of the abovementioned linear polymers using N, N'-bis(acryloyl)cystamine (BAC) as a redox responsive cross-linker. The described automated synthesis can be regarded as a proof-of-principle technique that next to emerging automated polymer purification and machine learning approaches could be useful to potentiate the development of autonomous methods for accessing systematic and comprehensive (peptide-)functionalized star polymer libraries. With these approaches hundreds of candidates of these complex polymer architectures could be rapidly synthesized, screened and optimized for different applications.

A one-step synthesis of nanotubes by RAFT dispersion polymerization of cyclodextrin/styrene (CD/St) complexes directly in water is presented. The resulted amphiphilic PEG-b-PS diblock copolymers self-assemble in situ into nanoparticles with various morphologies. Spheres, worms, lamellae, and nanotubes were controllably obtained. Because of the complexation, the swelling degree of polystyrene (PS) blocks by free St is limited, resulting in limited mobility of PS chains. Consequently, kinetically trapped lamellae and nanotubes were obtained instead of spherical vesicles. During the formation of nanotubes, small vesicles first formed at the ends of the tape-like lamellae, then grew and fused into nanotubes with a limited chain rearrangement. The introduction of a host-guest interaction based on CDs enables the aqueous dispersion polymerization of water-immiscible monomers, and produces kinetically trapped nanostructures, which could be a powerful technique for nanomaterials synthesis.

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.

In human body, alveoli are the primary sites for gas exchange which are formed by the dilation and protrusion of bronchioles at the end of the lung, and the rapid gas-exchanging process in the alveoli ensures normal life activities. Based on the unique structures and functions of alveoli, it is necessary to study the regulation mechanism of its formation, respiration, and apoptosis. Herein, a class of reversible addition-fragmentation chain transfer (RAFT)-derived amphiphilic triblock copolymers, PEO-b-P(DEAEMA-co-FMA)-b-PS is designed and synthesized. Due to the amphiphilic and gas-responsive segments, these triblock copolymers can self-assemble in aqueous solution and undergo the morphological transition from nanotubes to vesicles under gas stimulation; meanwhile, in the cycles of CO2 /O2 stimulation, these vesicles can further realize the volume expansion and contraction, eventually rupture. The gas-driven morphological transformations of these aggregates successfully imitate the formation, respiration, and apoptosis of alveoli, and provide an essential basis for revealing the life phenomena.

Potential-stimulated Pickering emulsions, using electrochemical responsive microgels as particle stabilizers, are prepared and used for biocatalysis. The microgels are constructed from cyclodextrin functionalized 8-arm poly(ethylene glycol) (8A PEG-CD) and ferrocene modified counterparts (8A PEG-Fc) via CD/Fc host-guest chemistry. Taking advantage of the redox reaction of Fc, the formation and deformation of the microgels and corresponding Pickering emulsions can be reversibly stimulated by external potential, and have been used for the hydrolysis of triacetin and kinetic resolution reaction of (R,S)-1-phenylethanol catalyzed by lipases. Potential stimulated destabilization of the emulsion realizes an effective separation of the products and enzyme recycling.

Research interest in electrochemical redox stimulus has grown considerably due to its easy trigger mode, in which the linkers have played important roles, such as the β-cyclodextrin-ferrocene (β-CD-Fc) linker. Star amphiphilic copolymers with well-defined and flexible structures are considered to be excellent choices for drug delivery systems (DDSs). Driven by the idea that using star polymers to improve the biocompatibility and efficiency of the β-CD-Fc-based DDS, we designed and synthesized star polymer 4 arm-poly(e-caprolactone)-β-CD ( 4A PCL-CD ) and linear polymer polyethylene glycol-Fc ( PEG-Fc ). They can form supramolecular block copolymer 4A PCL-CD / Fc-PEG and self-assemble to micelles, which are electrochemical responsive and can be applied as drug carriers for potential controlled release, with higher efficiency and better biocompatibility compared with their linear analogues.

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.

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.

Macromolecules have a strong tendency to interact with each other in solution to form a supramolecular structure through various secondary binding forces. In this study, nucleobase-containing templates poly(9-(4-vinylbenzyl)adenine) (PS AH) and poly(1-(4-vinylbenzyl)cytosine) (PS CH) are prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. Vinylbenzyl thymine (MS T) is polymerized in the presence of these two nucleobase-containing templates. MS T shows higher affinities toward the template PS AH compared with the template PS CH. In accordance with the Watson-Crick pairing principle, thymine forms hydrogen bonding (H-bonding) with adenine, but not between thymine and cytosine. A complex is formed when PS AH is used as template which indicates that there is a template polymerization of nucleobase complexes via molecular recognition.

One-step syntheses of well-defined Poly(3-((2-(Methacryloyloxy) ethyl) (dimethyl) ammonio)-1-propanesulfonate) (PDMAPS) with a carboxylic acid end-functional reversible addition-fragmentation chain transfer (RAFT) agent and further end-group modification were described. The upper critical solution temperature (UCST) of homo-zwitterions can be precisely adjusted by the surrounding pH due to the presence of a carboxyl end-group. Meanwhile, after esterification of the carboxylic acid group by methyl, ethyl, hexyl, phenethyl alcohol, UCST of all resulted PDMAPS with ester terminated groups showed more significant increases. Dynamic light scattering (DLS), Zeta-potential and small-angle X-ray scattering (SAXS) results demonstrated that the ionization/protonation from the carboxylic end-group and hydrophobicity of ester groups contribute significantly to the tunability. This end-group modification technique provides an easy and economical way of synthesizing temperature-responsive homo-polyzwitterions with precise and controllable temperature range owing to the designability of RAFT polymerization, where the products are suitable for biomedical and environmental engineering applications.

In this paper, we have developed epoxidized phenyl silicone rubber (EMVPQ) with good oil and radiation resistance by anionic ring-opening copolymerization and further epoxidation modification. Silicone rubbers with both phenyl and epoxy groups were firstly synthesized and main properties of the material were characterized. When the phenyl content in EMVPQ was increased from 5% to 20%, the damping loss peak shifted to the high temperature by 36 °C and the effective damping temperature range was widened by 3 °C. The tensile strength of EMVPQ with 20% phenyl content did not change before and after irradiation. When the epoxy content is only 13%, the EMVPQ retained mechanical properties after immersion at 25 °C or 100 °C for 72 h, but a commercial sample substantially lost its mechanical properties. This work not only promotes the research of epoxidized phenyl silicone rubber, but also opens an effective way for the preparation of high-performance aerospace materials.

Biological cyclization is highly efficient, and this can be attributed to the conformation of the backbone of the biopolymer. Taking advantage of metal-coordination geometry, we developed a method for conformation-directed polymerization cyclization through rational design of metal carbonyl monomers that could be used to produce cyclic macromolecules, even in bulk. P FpR [P Fp=(PPh2 (CH2 )3 Cp)Fe(CO)2 with the phosphine group tethered on the cyclopentadiene (Cp) ring; R=CH3 or (CH2 )5 CH3 ] was designed and synthesized for migration insertion polymerization to generate P(P FpR) with the polymer backbone containing Cp-Fe bonds. Growth of the backbone led to a cyclic conformation with close end-to-end distances, which facilitated the cyclization. This conformation-directed cyclization was attributed to the piano-stool metal-coordination geometry of the repeating units and the low rotational barrier of the Cp-Fe bonds in the backbone. The produced macrocycles, which contain a metal carbonyl coordination structure in their backbones, are rigid, unlike many organic macrocycles. The macrocycles thus have a large excluded volume. This new type of metal carbonyl macrocycle will be of interest as a building block for supramolecular chemistry and in the exploration of novel materials.

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.

Electrochemical stimuli have attracted much attention in recent years as they are simple, clean and can be widely applied in biological systems and material science. As one type of common guest molecules, ferrocene and its derivatives have been well studied with different host molecules, mainly including cyclodextrins, cucurbiturils, pillararenes and calixarenes. This article generally summarizes the recent work on the host-guest interactions between ferrocene derivatives and their host molecules, as well as various supramolecular systems based on these interactions. In addition, the development and outlook of electrochemical responsive systems are also discussed.

Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) with a β-cyclodextrin (β-CD) at the chain end was synthesized via atom transfer radical polymerization (ATRP); poly(e-caprolactone) (PCL) with a −C═C– segment and an adamantane (Ada) group at two ends, respectively, was prepared through ring-opening polymerization (ROP), and poly(N-isopropylacrylamide) (PNIPAM) with a −S–C(S)–S– segment, which can be converted into a thiol group, was yielded by reversible addition–fragmentation chain transfer polymerization (RAFT). A supramolecular triblock stimuli-responsive copolymer PNIPAM-b-PCL-b-PDMAEMA having good biocompatibility with PNIPAM and PDMAEMA hydrophilic segments and PCL hydrophobic segment was constructed by thiol–ene Michael addition and host–guest interaction. The triblock copolymer could self-assemble into vesicles and respond to carbon dioxide (CO2) gas and temperature reversibly. Under the stimulation of CO2, the vesicular assemblies swelled obviously; while raising the temperature from 25 to 40 °...

In the past decade, polymer vesicles prepared by self-assembly techniques have attracted increasing scientifi c interest based on their unique features highlighted with tunable membrane properties, versatility, stability, and capacity of transporting hydrophilic as well as hydrophobic species. Polymersomes exhibit intriguing potential applications such as cell mimicking dimensions and functions, tunable delivery vehicles, for the templating of biomineralization, nanoreactors, and as scaffolds for biological conjugation. In this Feature Article, an overview of the preparation and application of recently developed “smart” polymer vesicles, which can respond to the novel external stimuli, including carbon dioxide (CO 2 ), electrochemical potential, ultrasound, enzyme, near-infrared light, and magnetic fi eld is given. The response mechanism and morphology change are explored with specifi c focus on the functionalization of various domains of the polymer vesicles. In addition, the current limitations are explored as well as the challenges facing the development of these nanostructures toward real-world applications.

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.

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.

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.

Despite numerous studies on utilizing polymeric vesicles as nanocapsules, fabrication of tunable molecular pathways on transportable vesicle walls remains challenging. Traditional methods for building penetrated channels on vesicular membrane surface often involve regulating the solvent polarity or photo-cross-linking. Herein, we developed a neat, green approach of stimulation by using CO2 gas as “molecular drill” to pierce macroporous structures on the membrane of polymersomes. By simply introducing CO2/N2 gases into the aqueous solution of self-assemblies without accumulating any byproducts, we observed two processes of polymeric shape transformation: “gas breathing” and “gas piercing.” Moreover, the pathways in terms of dimension and time were found to be adjustable simply by controlling the CO2 stimulation level for different functional encapsulated molecules in accumulation, transport, and releasing. CO2-breathing and piercing of polymersomes offers a promising functionality to tune nanocapsules for encapsulating and releasing fluorescent dyes and bioactive molecules in living systems and also a unique platform to mimic the structural formation of nucleus pore complex and the breathing process in human beings and animals.

Electrochemical stimuli have attracted much attention in recent years as they are simple, clean and can be widely applied in biological systems and material science. As one type of common guest molecules, ferrocene and its derivatives have been well studied with different host molecules, mainly including cyclodextrins, cucurbiturils, pillararenes and calixarenes. This article generally summarizes the recent work on the host–guest interactions between ferrocene derivatives and their host molecules, as well as various supramolecular systems based on these interactions. In addition, the development and outlook of electrochemical responsive systems are also discussed.

CO2-responsiveness is imported into amphiphilic block copolymers, poly[(N,N-diethylaminoethyl methacrylate)-b-(N-isopropylacrylamide)] (PDEAEMA-b-PNIPAM), and a system dual-responsive to CO2 and temperature is constructed. The copolymer self-assembles in aqueous solution, and undergoes phase transition when CO2 and temperature stimuli occur, since the stimuli give rise to the conversion of the hydrophilicity of both blocks. Combining CO2 and temperature as triggers, schizophrenic micelle to vesicle morphological transition of the polymer assemblies is controlled.

CO2-responsiveness is imported into amphiphilic block copolymers, poly[(N,N-diethylaminoethyl methacrylate)-b-(N-isopropylacrylamide)] (PDEAEMA-b-PNIPAM), and a system dual-responsive to CO2 and temperature is constructed. The copolymer self-assembles in aqueous solution, and undergoes phase transition when CO2 and temperature stimuli occur, since the stimuli give rise to the conversion of the hydrophilicity of both blocks. Combining CO2 and temperature as triggers, schizophrenic micelle to vesicle morphological transition of the polymer assemblies is controlled.

The end-decorated homopolymer poly(ε-caprolactone)-ferrocene threaded onto a β-cyclodextrin-functionalized main-chain polymer can form a class of amphiphilic noncovalent graft copolymers based on the host-guest interactions of the terminal groups on the side chains. These new supramolecular polymer brushes can further self-assemble into micellar aggregates that exhibit reversible assembly and disassembly behavior under an electrochemical redox trigger, which opens up a new route to building dynamic block copolymer topologies.