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In this paper, tiny amount of methacryloxyethyl trimethylammonium chloride (DMC) was added in poly(vinyl alcohol) (PVA) in order to widen its thermoplastic processing window. The effects of DMC content on thermal, mechanical, optical, and water resistance were investigated. The results showed that the thermal stability of PVA/DMC was improved obviously. Compared with pure PVA, with tiny amount (∼0.6 wt%) of DMC, the initial decomposition temperature and the fastest decomposition temperature of DMC/PVA increased from 246 °C and 287.6 °C–320.8 °C and 364.8 °C respectively. Moreover, this tiny amount of DMC did not affect the crystallization performance of PVA. PVA/DMC (0.6 wt%) blend have similar mechanical, optical properties and low temperature water resistance as those pure PVA have. The melting temperature of the PVA/DMC remained at 221 °C as that of pure PVA. This work might provide a new method for widening the thermoplastic processing window of PVA without sacrificing its other inherent properties. The reasons why DMC could improve the thermal stability for PVA was explored as well.

We propose a pressure-induced flow (PIF) processing method for the simultaneous enhancement of strength, toughness, and heat resistance of biodegradable poly(butylene succinate) (PBS). The pressure and temperature were systematically adjusted to optimize the tensile strength of PBS. Under the optimized processing conditions, the structured PBS was characterized by relatively high strength of 89.5 MPa, toughness of 21.4 kJ·m−2, and improved heat resistance without deterioration of much of its ductility. Microscopic analyses witnessed denser and highly oriented crystalline domains along the flow direction caused by PIF processing. Detailed crystallization analysis made by 2D-WAXD and 2D-SAXS unraveled the extremely ordered PBS domains, which were featured by a significant increase in the orientation degree from 0.25 for the reference to 0.73 for PIF-processed PBS. Such a highly ordered microstructure substantially boosted the degree of crystallinity and heat-resistance temperature of PBS. We believe that our findings would offer a facile, green, and cost-effective approach for fabricating biodegradable polymers with outstanding properties and performance.

Dielectric material is an important material for film capacitors. However, the progress of this material is either impeded by its low dielectric constant, high loss tangent, or insufficient flexibility. In this work, PVA/GO film with alternating layer structure was fabricated by Spin-Coating-Assembly (SCA) method. This alternating layer structure not only benefits forming numerous microscale capacitors which improve e value a lot, but also helps eliminate perpendicular contact of GO and prevents the formation of conductive pathways. Thus, compared with pure PVA, significantly increased dielectric permittivity and a low loss tangent were simultaneously observed for the PVA/GO film. The ratio of dielectric permittivity to loss tangent increased from 68 to 165. These films might be potential flexible dielectric materials for advanced electrical devices such as embedded capacitors.

A triple interpenetrating polymer network (IPN) with dual responses to temperature and pH was constructed based on chemical crosslinking and electrostatic interaction. In this IPN, CaCO3 microspheres were used as the kernel and PNIPAAM/sodium alginate microcapsules were prepared by the inverse emulsion polymerization method. Research results demonstrated that CaCO3 kernels were decomposed into Ca2+ and CO2 at pH 1.2. Such decomposition facilitated the formation of triple IPN of Ca2+ crosslinking. Moreover, microcapsules were expanded by tension of CO2 and the volume increased to 3.55 × 105 times that of the original microcapsules, with capsules remaining an intact morphology. These microcapsules loading doxorubicin hydrochloride (DOX) stability and responses to environment were investigated. No drug overflow was observed at pH 7.4, indicating the high stability of microcapsules. However, DOX was released gradually in the simulated human stomach acid with a weak solution of hydrochloric acid (pH 1.2, 37 °C). This showed that the prepared microcapsules were feasible for drug-loaded capsules and the controlled drug release behavior could relieve side effects of drugs to human body. Moreover, it will help to increase the drug utilization and realize accurate treatment.

Continuously growing interest in the controlled and tunable transport or separation of target molecules has attracted more attention recently. However, traditional “on–off” stimuli-responsive membr...

Two nanocomposites with a hierarchical structure (GO@CuSilicate@Fe3O4 and GO@Fe3O4@CuSilicate) were fabricated in this paper. These as-synthesized nanocomposites were analyzed for their structural,...

Convenient, low-cost chemosensors for hazardous mercury ion detection have been receiving more and more attention in recent studies. However, most of these practical studies are based on an ideal sterile detecting atmosphere and ignore the role of bacteria in actual Hg(II) analytes. Herein, we demonstrate a new type of hydrophilic semi-IPN fluorescent polyHEAA hydrogel chemosensors fabricated by UV polymerization in situ interpenetrating fluorescent polymer PA-NDBCB with a polyHEAA network. Because of specific intermolecular interaction, i.e., hydrogen bonding between hydrophilic fluorescent polymer and polyHEAA matrix comprising a distinct semi-IPN structure, the mechanical property of bulk fluorescent hydrogels can be greatly improved over that of pure polyHEAA hydrogels. Moreover, the design of the hydrogel chemosensors rely on the highly efficient cyclization reaction between Hg(II) ions and the thiourea moieties that induce a visible "green-to-blue" fluorescence color change. On account of the hydrophilic porous structures, these hydrogel chemosensors achieve ultrafast, sensitive, selective Hg(II) detection (detection limit of 0.067 μM) and enable facile ratiometric actual detection in real-world aqueous system. Notably, they maintain fluorescence emission and detection property even under long-term coculture in a complex

Bio-sourced hydrogels are attractive materials for diagnosing, repairing and improving the function of human tissues and organs. However, their mechanical strength decreases with an increase in water content. Furthermore, it is challenging to mold these hydrogels with high precision, which significantly limits their applications. Herein, we modified a biocompatible and biodegradable material, hyaluronic acid, with methacrylic anhydride and then cured it with a four-arm star structure cross-linking agent under ultraviolet light. The hyaluronic acid hydrogel was finally cured within 15 s with an adjustable cross-linking degree. The results demonstrated that the developed gel maintained good mechanical strength with a water content of 90%, while achieving micropatterns at a precision of 20 μm. The biological experiments showed that it could effectively promote the release of vascular endothelial growth factor (VEGF), which contributed to promoting cell growth, and has favorable biocompatibility. Overall, this hyaluronic acid hydrogel is a promising biomedical material with high forming accuracy, excellent mechanical properties, and favorable biocompatibility, which indicate its potential value in a variety of tissue engineering and biomedical applications.

Polyzwitterionic brushes with strong anti-polyelectrolyte effect have shown great potential as smart surfaces for tunable lubrication, protein absorption/desorption, and bacteria killing and release. However, due to the brush structure in which polymer chain is tethered on the substrate by one end, this surface is easily destroyed from the detachment of the brush, greatly limiting its real-world applications. To solve this problem, herein, cross-linked structure was introduced in poly(3-(dimethyl (4-vinylbenzyl) ammonium) propyl sulfonate) (polyDVBAPS) brushes to offer the long-term stability. The cross-link structure was fabricated by adding a cross-linker during the surface initiated atom transfer radical polymerization, and the effect of such structure on the surface morphology, salt-responsive behavior, and long-term stability were investigated. The results indicated that the cross-link structure with tunable cross-link density could be readily prepared by this method. The responsive behaviors, such as switch between friction and lubrication, bacteria release in response to salt solution, were well-retained by the cross-linked polyDVBAPS brush. More importantly, high long-term stability was endowed by the cross-link structure, from which the cross-linked brush not only showed long-time lubrication and high load resistance during friction measurements, but also exhibited a high retention ratio (more than 90%) of bacteria release capability even after 30 water/salt solution switch cycles, in contrast, the non-cross-linked brush showed a low retention ratio of ˜50% after the similar treatment. These results indicated that cross-linked structure could be an efficient method to enhance the stability of responsive polymer brushes and greatly strengthen the practicability of such brushes in real-world applications.

“Janus-featured” hydrogels with different structure and function for each layer can be particularly important in diverse application. However, very few studies have been conducted on multifunctiona...

This paper reports a novel routine for the fabrication of a polycaprolactone-derived (PCL-derived) photocured material cross-linked by pentaerythritol tetra (PETMP) with enhanced mechanical property and excellent biocompatibility. The photocured material is cross-linked via UV irradiation through thiol-ene “click” chemistry. The main novelty of this technique is the facile fabrication of high-resolution patterns (∼5 μm) using photolithography, and without adding photo-initiators. The photocured material is studied regarding to its thermal property, mechanical property and cytocompatibility. DSC and DMA suggest that the flexibility and toughness of PCL-derived photocured material have improved. Accordingly, the PCL-derived photocured material achieves enhanced mechanical property (with the increase of PCL segment content from 0 to 38.0%, the photocured samples monotonically increased their breaking strength from 0.62 to 3.10 MPa and Young’s modulus from 1.39 to 9.22 MPa). Due to the incorporation of the PCL-derived copolymer, the material shows excellent affinity to cells, which is demonstrated by the cell proliferation and release of LDH. The hemolysis ratio of PCL-derived photocured materials is all

Bilayer hydrogels are one of the most promising materials for use as soft actuators, artificial muscles, and soft robotic elements. Therefore, the development of new and simple methods for the fabrication of such hydrogels is of particular importance for both academic research and industrial applications. Herein, a facile, one-pot, and one-step methodology was used to prepare bilayer hydrogels. Specifically, several common monomers, including N-isopropyl acrylamide, acrylamide, and N-(2-hydroxyethyl)acrylamide, as well as two salt-responsive zwitterionic monomers, 3-(1-(4-vinylbenzyl)-1H-imidazol-3-ium-3-yl)propane-1-sulfonate (VBIPS) and dimethyl-(4-vinylphenyl)ammonium propane sulfonate (DVBAPS), were chosen and employed with different combinations and ratios to understand the formation and structural tunability of the bilayer hydrogels. The results indicated that a salt-responsive zwitterionic-enriched copolymer, which could precipitate from water, plays a dominant role in the formation of the bilayer structure and that the ratio between the common monomer and the zwitterionic monomer had a significant effect on the structure. Due to the salt-responsive properties of polyVBIPS and polyDVBAPS, the resultant bilayer hydrogels exhibited excellent bidirectional bending properties in response to the salt solution. With the optimal monomer pair and ratio determined, the bend of the hydrogel could be reversed from ∼-360 to ∼266° in response to a switch between water and a 1.0 M NaCl solution. Additionally, this method was further used to fabricate small-scaled patterns with structural and compositional distinction in two-dimensional hydrogel sheets. These two-dimensional hydrogel sheets exhibited complex and reversible three-dimensional shape transformations due to the different bending behaviors of the patterned hydrogel stripes under the action of an external stimulus. This work provides greater insight into the mechanism of the one-step, one-pot method fabrication of bilayer hydrogels, demonstrates the ability of this method for the preparation of small-scale patterns in hydrogel sheets to endow the complex with a three-dimensional shape transformation capability, and hopefully opens up a new pathway for the design and fabrication of smart hydrogels.

A new method was proposed for fabricating the polymer foams with bimodal structure. Briefly, nanoparticles and polymer powders were dry-mixed by ball-milling and then hot-pressed into the composites in which nanoparticles were selectively distributed at the interfaces between polymer multi-facets. Upon batch foaming using scCO2 as blowing agent, bimodal structure was generated due to the selective distribution and heterogeneous nucleation effect of the nanoparticles. Using this method, several bimodal composite foams based on different nanoparticles, i.e. graphene, carbon nanotubes, and silica nanoparticles and different polymers, i.e. thermoplastic polyurethane (TPU) and polystyrene (PS) were successfully fabricated. Specifically, TPU/graphene system was systemically studied. The results showed that the foam morphologies could be easily tuned by changing nanoparticle content, particle size of polymer powder, hot-pressing temperature and pressure, as well as foaming conditions (e. g. foaming temperature and pressure), indicating the great simplicity and tune-ability of this method.

Development of novel materials with dual antibacterial and antifouling functions is important for many bio-applications. In this work, we design and synthesize a series of mixed polymer brushes grafted from silica surface as a new type of antibiofouling and antimicrobial coating, which combine poly(N-hydroxyethyl acrylamide) (polyHEAA) synthesized by atom transfer radical polymerization (SI-ATRP) and cationic poly(trimethylamino) ethyl methacrylate chloride, polyMETAC) synthesized by photoiniferter-mediated polymerization (SI-PIMP). The surface composition, charge and morphology of the resultant mixed polymer brushes are carefully characterized and optimized by tuning ATRP and PIMP initiator ratios. The mixed polymer brushes possess strong bacterial killing ability from polyMETAC chains and high antifouling property from polyHEAA chains. At the optimal conditions, the mixed polyHEAA/polyMETAC brushes exhibit excellent anti-bacterial adhesion property by retaining ultralow cell adhesion of ˜3.0 × 105 cells/cm2 and high contact killing efficiency by killing more than 90% attached bacteria of Escherichia coli and Staphylococcus. Long-term antibacterial performance indicated the cell adhesion was retained at ultralow level of 5 × 105 cells/cm2 even after 72 h exposure to bacteria solution. The results indicate that surface grafting with polyHEAA and polyMETAC can be potentially useful for long-term biomedical and biomaterial applications.

This paper explored the injection foaming process of in situ fibrillation reinforced polypropylene composites. Using polypropylene (PP) as the continuous phase, polytetrafluoroethylene (PTFE) as the dispersed phase, multi–wall carbon nanotubes (MWCNTs) as the conductive filler, and PP grafted with maleic anhydride (PP–g–MA) as the compatibilizer, a MWCNTs/PP–g–MA masterbatch was prepared by using a solution blending method. Then, a lightweight, conductive PP/PTFE/MWCNTs composite foam was prepared by means of extruder granulation and supercritical nitrogen (ScN2) injection foaming. The composite foams were studied in terms of rheology, morphological, foaming behavior and mechanical properties. The results proved that the in situ fibrillation of PTFE can have a remarkable effect on melt strength and viscoelasticity, thus improving the foaming performance; we found that PP/3% PTFE showed excellent performance. Meanwhile, the addition of MWCNTs endows the material with conductive properties, and the conductivity reached was 2.73 × 10−5 S/m with the addition of 0.2 wt% MWCNTs. This study’s findings are expected to be applied in the lightweight, antistatic and high–performance automotive industry.

Near-infrared (NIR) responsive hydrogels are of significance in remote control microvalves. However, the development and the application of NIR responsive hydrogels were either limited by high cost or limited by long response time (on the order of minutes) and modest volume change. To address this problem, in this work, a graphene oxide@polyaniline (GO@PANI) hybrid nanocomposite with nanorod array hierarchical structure was fabricated by dilute polymerization. The as-synthesized hierarchical GO@PANI nanosheets exhibited high NIR photothermal conversion efficiency (PTCE) (49%), which was approximately 188% the magnitude of that of GO sheets. Due to its high photothermal conversion efficiency, when GO@PANI was incorporated into temperature-responsive poly(N-isopropylacrylamide) (PNIPA), a highly responsive hydrogel with rapid and significant NIR-induced volume change (over 50%) was obtained. When this material was applied as a remote-controllable microvalve, it exhibited a fast NIR response (∼30 s).

Convenient, low-cost chemosensors for hazardous mercury ion detection have been receiving more and more attention in recent studies. However, most of these practical studies are based on an ideal sterile detecting atmosphere and ignore the role of bacteria in actual Hg(II) analytes. Herein, we demonstrate a new type of hydrophilic semi-IPN fluorescent polyHEAA hydrogel chemosensors fabricated by UV polymerization in situ interpenetrating fluorescent polymer PA-NDBCB with a polyHEAA network. Because of specific intermolecular interaction, i.e., hydrogen bonding between hydrophilic fluorescent polymer and polyHEAA matrix comprising a distinct semi-IPN structure, the mechanical property of bulk fluorescent hydrogels can be greatly improved over that of pure polyHEAA hydrogels. Moreover, the design of the hydrogel chemosensors rely on the highly efficient cyclization reaction between Hg(II) ions and the thiourea moieties that induce a visible “green-to-blue” fluorescence color change. On account of the hydrop...

Developing new smart hydrogel systems and new fabrication methods is critical for fundamental research and industrial applications, particularly in the intelligent human–machine field, but still faces great challenges. In this work, we present bilayer poly(N-isopropylacrylamide)/graphene oxide (polyNIPAM/GO) hydrogels with dual thermo- and near-infrared (NIR)-responsive properties using a simple, in situ polymerization-centrifugation method. By tuning the GO concentration and centrifugation speed, a transparent polyNIPAM layer and a dark-brown GO-rich layer are formed, where each layer displays distinct network structures and swelling behavior. Due to the asymmetric double-layer structure, the polyNIPAM/GO bilayer hydrogels enable one to realize fast, controllable, bidirectional bending under thermal or NIR stimulation within 1 min, and the bending orientation and degree can be reversibly, repeatedly, and precisely controlled by the temperature- or NIR-induced cooperative swelling–shrinking properties of both layers. Based on the reversible, bi-directional bending nature of polyNIPAM/GO hydrogels, we further design two proof-of-concept hydrogel actuators to highlight the advantages of this hydrogel system: one acts as a wiggler to mimic robot arms to move objects, while the other serves as an electric switch to turn on/off a light. In addition, our polymerization-centrifugation method can also be used to prepare polyNIPAM/SiO2 bilayer hydrogels, demonstrating its general applicability to other polyNIPAM–nanoparticle hydrogels with a bilayer structure. This work provides both a new fabrication method and hybrid hydrogel systems for the development of smart, programmable, and versatile hydrogel-based actuators.

Surfaces with stimuli-responsive properties have shown prominent applications in bioengineering, controlled drug release and biosensors in recent years. In this work, we report a surface-initiated reversible addition–fragmentation chain transfer polymerization method to graft azobenzene-containing diblock copolymer (azo-BCP) brushes onto an Indium Tin Oxide (ITO) glass surface. In this method, a sequential azo block serves as the outer layer that controls the closure or opening of the brushes, and the second block (PDMAEMA) acts as the inner layer that switches between swollen and collapsed chain states in response to different pH values and temperatures. Upon exposure to UV light, the ITO surface became more hydrophilic (>10° change of contact angles), and its friction coefficient (0.5–0.9) increased; this suggests a loose aggregation of the azo block. Additionally, the ion conductivity of the ITO surface can be influenced by the aggregation state of the azo-BCP brushes, thus leading to the transportation of light-triggered ions under various pH values and temperatures. This work provides a deep understanding of the surface properties of a sensitive hybrid material upon various stimuli for electrode purpose, thereby paving the way for the development of bioengineering and environmental sensory applications.

Lignin is the most abundant and important macromolecule in organic matter and its yield is second only to cellulose. Lignin is abundant in source, low in price, and has a large number of active groups such as methoxy group and carboxyl group, so it has great utilization value. We used lignin as a carbon source to prepare porous carbon nanosphere (PCN) materials, and in-situ synthesized the MoS2 on its surface. The high specific surface area (∼462.8 m2/g), large pore volume and good electron conductivity of the porous carbon scaffold facilitated the reversible electro-chemical reaction of S towards metallic Li, and thus the nano-hybrid showed a high specific energy and excellent cycle stability which still remained 520 mAh/g after 50 cycles.

Polydimethylsiloxane (PDMS) is a common biomaterial with excellent properties. However, its inherent hydrophobicity impedes cell growth and differentiation. PDMS is an intrinsically inert material, which limits its applications to specific scenarios where responsive materials are needed. Dopamine can easily adhere to various substrate surfaces through noncovalent and covalent interactions. In this work, a bioinert PDMS surface was modified into a bioactive surface by biocompatible and pH-sensitive polydopamine (PDA). The binding of PDA and PDMS in different forms was verified by the typical scanning electron microscopy (SEM) and atomic force microscope (AFM). By PDA film modification, the contact angle of PDMS was significantly reduced. Hydrophobicity was achieved by PDA nanosphere (PDA NS) modification. PDA-modified PDMS was also found to be pH-sensitive, as validated by contact angle measurement, macroscopic friction test, and protein adsorption. Compared to an unmodified surface, the PDA significantly improved cell adhesion, proliferation and spreading. We came to a conclusion that the surface roughness of PDA-modified PDMS had little effect on cell growth and the cytocompatibility of the materials was mainly determined by the surface chemical properties. Our results further validated that PDA/PDMS is pH-sensitive and can effectively promote cell growth and proliferation.

The use of stabilizers in liquid-phase exfoliation of graphite can effectively promote graphite exfoliation in common solvents, and concurrently render functionalized graphene by adsorbing them on the exfoliated graphene surface. Thus, the exploration of novel stabilizers is especially important for graphene liquid-phase production and related applications. Herein, we report the successful application of a pyrene-functionalized hyperbranched polyethylene (HBPE@Py) as the stabilizer for graphite exfoliation in chloroform. The polymer has a global hyperbranched polyethylene backbone and multiple covalently bonded pyrene moieties as branch ends. It can be synthesized via ethylene copolymerization using a Pd-diimine catalyst under mild conditions, 0.1 MPa/25 °C. Due to the cooperative effect of the CH-π and π-π interactions between the HBPE@Py and graphene surface, some of the polymer is irreversibly adsorbed on the latter, thus effectively preventing their re-stacking and concurrently rendering pyrene-functionalized graphene. This allows us to obtain stable dispersions of few-layer graphene with relatively high concentrations (0.10–0.50 mg mL−1) and exfoliation efficiencies (1.6–13.0%). The resultant graphene is confirmed to be high-quality and shown to be highly stable when dispersed in chloroform, even the free polymer has been thoroughly removed. From the dispersion, a flexible, conductive graphene film and polymer-based graphene nanocomposites have been successfully prepared.

Zwitterionic polymer brushes with strong anti-polyeletrolyte effect have shown great potential in applications of tunable friction, protein absorption/desorption, and “killing and release” antibacterial surfaces. However, such polymer brushes are presently prepared by surface-initiated atom transfer polymerization (SI-ATRP) which is a sophisticated and time-consuming process. In this paper, a simple method, i.e. surface-initiated photoiniferter-mediated polymerization (SI-PIMP) was used to prepare poly (3-(dimethyl (4-vinylbenzyl) ammonio) propyl sulfonate) (polyDVBAPS) brush on silicon wafer. It was shown that the reaction solution had a significant effect on the growth rate and surface roughness of the resulting brushes. In suitable solution (e.g. 0.53 M NaCl solution) brushes with controllable thickness and smooth surface could be obtained. Contact angle and surface friction measurement indicated that the brush prepared by SI-PIMP showed identical salt-responsive properties compared to the brushes from SI-ATRP. In addition, the thermo-responsive properties of polyDVBAPS brush was also investigated, which was further used for tuning surface friction of the brush. Due to the thermo-responsive properties, polyDVBAPS brush showed super lubrication (u ∼ 10−3) in water and NaCl solutions with low concentrations (0.1 M and 0.53 M) when the temperature was increased to 70 °C, 65 °C and 55 °C respectively. Although ultralow friction could be achieved under the conditions of different temperature and salt concentration, the stability against long-term friction highly depended on the environmental condition. At 40 °C and in 1.0 M NaCl solution, ultralow friction was well retained up to 1500 s, while under other conditions (saturated NaCl solution of 25 °C and 0.53 M NaCl solution of 55 °C), aqueous lubrication was rapidly deteriorated. This work not only demonstrated the practicability of the SI-PIMP for the preparation of polyDVBAPS brush, but also realized the tunable surface friction of such polyzwitterionic brush under different environmental conditions, extending its applications in both academic and industrial communities.

Stimuli-responsive surfaces with switchable bacterial killing and release are new promising candidates for the development of new antibacterial materials. Although such surfaces have been extensively studied and many advances have been achieved, a number of challenges are remained, including the optimization of structure, moderate stimuli, and so forth. In this paper, we developed a new “killing and release” antibacterial surface by combining poly[2-(tert-butylamino) ethyl methacrylate] (polyTA) and poly(3-(dimethyl (4-vinylbenzyl) ammonio) propyl sulfonate) (polyDVBAPS) via mixed brushes system. The bactericidal activity of polyTA and salt-responsive property of polyDVBAPS could be well integrated in this way. Accordingly, the surface showed high bactericidal activity by killing more than 94% attached bacteria of E. coli and S. aureus and excellent release capability by detaching most attached bacteria in response to salt solution. Both bacterial killing effectiveness and release rate were well retained ...

Development of smart soft actuators is highly important for fundamental research and industrial applications but has proved to be extremely challenging. In this work, we present a facile, one-pot, one-step method to prepare dual-responsive bilayer hydrogels, consisting of a thermoresponsive poly( N-isopropylacrylamide) (polyNIPAM) layer and a salt-responsive poly(3-(1-(4-vinylbenzyl)-1 H-imidazol-3-ium-3-yl)propane-1-sulfonate) (polyVBIPS) layer. Both polyNIPAM and polyVBIPS layers exhibit a completely opposite swelling/shrinking behavior, where polyNIPAM shrinks (swells) but polyVBIPS swells (shrinks) in salt solution (water) or at high (low) temperatures. By tuning NIPAM:VBIPS ratios, the resulting polyNIPAM/polyVBIPS bilayer hydrogels enable us to achieve fast and large-amplitude bidirectional bending in response to temperatures, salt concentrations, and salt types. Such bidirectional bending, bending orientation, and degree can be reversibly, repeatedly, and precisely controlled by salt- or temperature-induced cooperative swelling-shrinking properties from both layers. Based on their fast, reversible, and bidirectional bending behavior, we further design two conceptual hybrid hydrogel actuators, serving as a six-arm gripper to capture, transport, and release an object and an electrical circuit switch to turn on-and-off a lamp. Different from the conventional two- or multistep methods for preparation of bilayer hydrogels, our simple, one-pot, one-step method and a new bilayer hydrogel system provide an innovative concept to explore new hydrogel-based actuators through combining different responsive materials that allow us to program different stimuli for soft and intelligent materials applications.

Most high capacity anode materials expand significantly during charging, such anodes must contain sufficient porosity or tough protective layer in the discharged state to enable the expansion, yet not excess porosity or low mobility of mass, which lowers the overall energy density. Here, we present a high capacity anode consisting of hierarchical mesoporous carbon nanospheres without any additives, which are derived from lignosulfonate and can be used as an excellent support for in-situ embedding NiO nanoparticles of 11 wt%. The as-prepared hybrid nanospheres have an integrated architecture with micropore-to-mesopore distribution and a surface area of 852 m2 g−1. As a result, the hybrid nanosphere anode exhibit a high discharging capacity of 863 mAh·g−1 at 0.1 A g−1 is retained after 100 cycles for a Li-ion battery. When evaluated as an electrode material for supercapacitors, the as-prepared hybrid nanospheres manifest exceptional performance with a high pseudocapacitance of 508 F g−1. Remarkably, about 92% of the initial capacitance can be retained after 2000 charge/discharge cycles. This approach generates a strategy to combine metal oxide nanoparticles with nanostructured carbon derived from biomass, which is expected for a broad set of possible electrode chemistries.

In this work, a series of the thermoplastic elastomer (TPE) composites filled with micro CaCO3 and hollow glass microspheres (HGM) via alloying process were investigated. The plastic phase of TPE c...

Polymer brushes have been demonstrated as versatile and effective surface modification method to achieve unparalleled control over surface properties and functionality. Here, this review mainly highlights the intriguing performance and functionalities of zwitterionic polymer brushes with anti-polyelectrolyte property for a variety of applications in protein resistance, antibacterial activity, surface wetting, and surface frication. Different from other hydrophilic polymer brushes, zwitterionic brushes exhibit the unique zwitterionic-induced anti-polyelectrolyte effect, allowing for the development of new smart polymers and polymer-coated surfaces.

Antibacterial surfaces that not only can kill bacteria but also can release the dead bacteria have become one of most promising antibacterial strategies, but the realization of high efficiency, rapid response and long-term reusability of such surfaces remains many challenges. Herein, we reported new antibacterial surfaces with high killing and release capabilities based on a salt-responsive brush recently developed by our group. These surfaces consist of two polymer brushes with two-layer architecture, where the upper-layer bactericidal brushes (poly[(trimethylamino) ethyl methacrylate chloride], polyMETAC or poly[2-(tert-butylamino)ethyl methacrylate], polyTA) were built on background layer of salt-responsive polyzwitterionic brush (poly(3-(dimethyl(4-vinylbenzyl) ammonio) propyl sulfonate), polyDVBAPS) via sequential surface initiated atom transfer radical polymerization. By the combination in this manner, the bacteria attach/release function of polyDVBAPS and bactericidal function of polyMETAC/polyTA were successfully integrated, resulting in the smart surfaces which can reversibly kill and release bacteria in response to the switch between water and salt solution. Both two systems in this study, i.e. poly (DVBAPS-b-METAC) and poly(DVBAPS-b-TA), exhibit high bactericidal activity by killing more than 93% and highly efficient regeneration capability by rapidly releasing ∼90% of the attached bacteria. Specifically, such excellent antibacterial performance of poly(DVBAPS-b-TA) can be well retained even after four killing-release cycles, indicating the great potential in reusable biological materials and devices. Furthermore, the correlation between physicochemical properties of the two-layer brushes with their bactericidal efficiency and regenerative capability was also investigated and discussed.

Polymeric microcellular foams with high strength and light weight are very important for industrial applications. However, regulating their cell structure and their weak flame retardancy are problematic. We designed single-arm POSS-based ionic liquids ([bel-POSS][PF6]), and constructed hybrid composites based on physical interaction between ionic liquids and carbon-based materials in PS microcellular foaming. Ionization of bel-POSS could result in a quaternary ammonium reaction and ion-exchange reaction, and the carbon materials exhibit good dispersion through blending. The prepared hybrid composites showed high CO2 adsorption. Conical calorimeter tests showed that PS composite materials could reduce the heat release rate, total heat release, toxic gases (CO2 and CO) release, and amount of smoke generated. These carbon materials could affect PS micropore structure, including the cell diameter and density. Upon addition of 5 wt% of carbon materials, the hole diameter decreased by >50%, and the hole density increased nearly ten folds.

The development of new antimicrobial materials and strategies is of importance for many biomedical and industrial applications. In this work, we report a new strategy to integrate distinct antimicrobial, antifouling, and stimuli-responsive properties into a single hydrogel to realize bacteria resistance, killing, and releasing functions. To achieve this design, we conjugated salt-responsive anti-polyelectrolyte polyDVBAPS (poly(3-(dimethyl(4-vinylbenzyl)ammonio)propyl sulfonate)) with antifouling polyHEAA (poly(N-hydroxyethyl acrylamide)) and antimicrobial AgNPs (silver nanoparticles) to form a hybrid hydrogel of polyDVBAPS-g-polyHEAA@AgNPs, among which polyHEAA functions as a general antifouling background to prevent bacteria adsorption on the surface, AgNPs act as antimicrobial agents to kill bacteria on the surface, and polyDVBAPS uses its unique salt-responsive, anti-polyelectrolyte property to release adherent bacteria from the surface. In this design, polyDVBAPS-g-polyHEAA@AgNPs hydrogels not only effectively resist bacteria attachment and kill the adherent bacteria, but also regenerate the antifouling surface of the hydrogel by releasing the adhered bacteria to keep the surface free from bacteria. The polyDVBAPS-g-polyHEAA@AgNPs hydrogels exhibited high surface resistance to bacteria adsorption ( 96% of adherent live or dead bacteria from the surface upon a simple treatment of 1.0 M NaCl solution for 10 min. Upon the release of AgNPs, AgNPs were reloaded into the hydrogel again to achieve multiple antifouling, bactericidal, and regenerative properties. This work demonstrates a new design for a new multifunctional hydrogel to effectively achieve antimicrobial, antifouling, and surface regeneration properties, making this hydrogel very promising for antimicrobial applications.

It is still challenging to fabricate polymer foams with bimodal structure via a simple technique in the both industrial and academic fields. In this work, by mixing polydimethylsiloxane (PDMS) into thermoplastic polyurethane (TPU) and utilizing the difference of foaming dynamics between TPU and PDMS, the target foams with bimodal structures were successfully prepared through a one-step foaming process. It was shown that under the optimal conditions (i.e. PDMS content of 15 wt%, foaming temperature of 100 °C and foaming pressure of 13.8 MPa), the resultant foam possessed distinct bimodal structures with large cells of ~12 µm and small cells of ~3 µm. Such bimodal structures also help the forms to have the excellent compress strength and modulus of 506 kPa and 1618 kPa, which are much higher than the foam with uniform structure. In addition, bimodal structure foam has ~3 dB higher sound insulation than uniform structure foam.

We present a comprehensive research on the photo-induced multi-responsibility of azobenzene(azo) diblock copolymer (BPC) grafted from the surface of mesoporous silica as a light-triggered and controllable ions transport system. The surface-initiated RAFT method was used to grow sequentially a first poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block serving as an inner layer for the pH and thermal responsibility and a second terminal azo block functionalizing the trans-cis photoisomerization to control the closure or opening of the brushes in water. We show that the ions conductivity of hybrid system could be controlled by the second block switchable between the coil-recoil brush chain states in response to pH or temperature change or exposure to light. It was confirmed a suitable composition ratio of azo BPC brushes could significantly influence the hydrophilicity and polarity of the out layer with light, resulting the protonation or gelation of PDMAEMA block. For example, the Ru(NH3)63+ cations as probing ions was employed to prototyping the controlled permselectivity triggered by the UV light exposure. This kind of hybrid material is particularly interesting in the versatile utility for drug delivery, separating, biomimic sensor and so on.

A facile and general method for the large-scale preparation of various three-dimensional (3D) graphene oxide/metal–organic framework (GO/MOF) composites is developed through a simple mixing process using MOFs and graphene oxide. This preparation method is able to rapidly produce GO/MOF composite hydrogels with controllable composition in only several minutes, which is also suitable to a series of different MOFs. The obtained GO/MOF composites are severed as the precursors for the subsequent preparation of MOF-derived composite aerogels, e.g., rGO/Fe2O3 and rGO/NiO/Ni composite aerogels, through freeze-dry and calcination processes. When used as a supercapacitor electrode, the rGO/Fe2O3 composite shows a good rate capability with high specific capacitances of 869.2 and 289.6 F·g–1 at the current densities of 1 and 20 A·g–1, respectively, as well as a long cycle life without obvious decrease of capacitance after 5000 cycles. Moreover, the flexible all-solid-state supercapacitor device is also fabricated bas...