A novel S-ST/MWCNT/Kevlar-based wearable electronic textile (WET) with enhanced safeguarding performance and force sensing ability was fabricated. Stab resistance performance tests under quasi-static and dynamic conditions show that the maximum resistance force and penetration impact energy for the WET are 18 N and 11.76 J, which represent a 90% and 50% increment with respect to the neat Kevlar, respectively. Dynamic impact resistance tests show that the WET absorbs all the impact energy. The maximum resistance force of the WET is 1052 N, which represents an improvement of about 190% with respect to neat Kevlar. With the incorporation of multi-walled carbon nanotubes (MWCNTs), the WET can achieve a stable electrical conductivity of ∼10−2 S m−1, and the conductivity is highly sensitive to external mechanic forces. Notably, the sensing fabric also exhibits an outstanding ability to detect and analyze external forces. In addition, it can be fixed at any position of the human body and exhibits an ideal monitoring performance. Because of its flexibility, high sensitivity to various types of deformations and excellent safeguarding performance, the WET has a strong potential for wearable monitoring devices that simultaneously provide body protection and monitor the movements of the human body under various conditions.

We develop a modified method to improve the rheological performance of SiO2-based shear thickening fluid (STF). Directly adding surfactant into STF is the most common method to improve the rheological performance of SiO2-based STF. However, the final viscosity increases quickly with the increase of shear rate, which is against for the practical applications. In this work, SiO2 nanospheres are firstly modified by PVP K30 through an ethanol refluxing method and the modified SiO2 nanospheres are used to prepare PVP@SiO2-STF. Compared with the unmodified SiO2 based STF (SiO2-STF), the PVP@SiO2-STF presents an obvious increase of shear thickening (ST) effects and the maximum viscosity increases by 7 times and the critical shear rates decrease about 10 times approximately. A reasonable explanation is proposed to interpret the influence of the modification methods on the rheological properties of STF. This work provides a new way to control the shear thickening behavior and also contributes to understand the mechanism of ST effect, which has an important significance to develop controllable STF.

A simple and scalable “dip and dry” method was developed for fabricating stretchable polyurethane sponge-based polymer composite with excellent shear stiffening effect, creep resisting and adhesion property. The stiffness of the composite was tunable, the storage modulus (G′) could automatically increase 3 orders of magnitude with the increasing of shear frequency, and the G′max could reach to as high as 1.55 MPa. Importantly, the composite with ideal damping capacity reduced the impact force by 2 orders of magnitude even under 26 cycles of consecutive dynamic impact loading with no obvious mechanical degradation. Moreover, an enhancing mechanism was proposed and it was found the “B–O cross bond” and the entanglement of polymer chains were attributed to the shear stiffening characteristic. Finally, the excellent adhesion ability and hydrophobicity guarantee the composite with reliable mechanical performance and longer lifespan.Keywords: adhesion; energy dissipation; hydrophobicity; shear stiffening; stretchable polyurethane sponge

A novel rate-dependent and self-healing conductive composite with a well-defined shear stiffening (S-ST) effect was facilely fabricated by dispersing multi-walled carbon nanotubes (MWCNTs) into a shear stiffening polymer matrix. The storage modulus (G′) of the multi-functional composite automatically increased 4 orders of magnitude when encountering external shear stimuli and the G′max was over 1 MPa, demonstrating an obvious shear stiffening effect and good safe-guarding performance. It was found that the electrical conductivity changed accordingly when shear stiffening occurred, therefore it can be applied as a force sensor during the attacking process. The rate-dependent piezoresistance effect of the composite was investigated. In quasi-static compression and high rate impact tests, different force signals can be obtained because of the negative and positive piezoresistivity effect. Self-healing tests indicated that the as-prepared composite can maintain its mechanical and electrical properties after destruction and healing treatments. Owing to the shear stiffening performance, the rate dependent conductive composite could both absorb impact energy and sense the attacking forces. Finally, a mechanism was proposed and it was believed that the glass transition induced by B–O interactions and the changes in the microstructure during the external action can be attributed to the S-ST performance and rate dependent electrical conductivity, respectively.

A novel rod-like β-FeOOH@poly(dopamine)–Au–poly(dopamine) nanocomposite is developed for recyclable catalysis. Firstly, the rod-like β-FeOOH template was coated in situ by a layer of poly(dopamine) (PDA) to form a core/shell nanostructure. Then the negatively charged Au nanocatalysts were well-immobilized onto the periphery of the β-FeOOH@PDA nanorod. To protect the Au nanocrystals from leaching during the catalytic reactions, another PDA layer was coated onto the above particles to form a sandwich-like PDA–Au–PDA shell on the β-FeOOH rod core. The reduction of Rhodamine B (RhB) was introduced as a model reaction to evaluate the catalytic activity of the as-prepared nanocomposites. It was found that the catalytic rate sharply increased with an increasing amount of the nanocatalyst. Benefitting from the thin outer layer of PDA, the recyclability of the nanocatalyst dramatically increased. After five times of catalytic reaction, the activity was maintained as high as 98.3%, while the β-FeOOH@PDA–Au showed it to be retained at only 73.4%.

A novel multi-functional polymer composite (MPC) with both excellent shear stiffening (ST) performance and magnetorheological (MR) effect is prepared by dispersing magnetic particles into shear stiffening polymer matrix. Besides having the magnetically dependent mechanical properties (MR effects), this multi-functional MPC automatically changes its rheological behavior in response to external shear stimuli. The mechanical properties of this smart composite can be alternatively achieved by varying the particle's types and contents. Upon applying a shear stress with excitation frequency from 1 Hz to 100 Hz, the storage modulus (G′) of the MPC increases from 102 to 106 Pa, demonstrating an excellent ST effect. Interestingly, the ST effects of the MPC are also tunable by varying the external magnetic field, and the area of G′ could be greatly increased and precisely controlled. Based on the experimental results, a possible mechanism is proposed and discussed. It is believed that the “cross bonds” and the particle chains induced by the magnetic field are due to the excellent multi-functional stimulus-response properties.

•A novel kind of shear thickening fluid (STF) of polymer nanoparticles was developed.•The particles’ structure dependent of the STF rheology was studied.•A possible mechanism for the shear thickening (ST) behavior was proposed.•The surface charges and hardness of the particles strongly affected the ST effects.A novel kind of shear thickening fluid (STF) was developed via dispersing poly(styrene–acrylic acid) (PS–AA) nanospheres into ethylene glycol (EG). By varying the structure characteristics of the PS–AA particles, STFs with different rheological properties can be obtained. Firstly, the influence of the styrene/acrylic acid ratio on the PS–AA nanospheres was investigated. It was found that the higher ratio often led to the better shear thickening (ST) effects and under the optimum condition the maximum viscosity of the STF could reach to 152 Pa s, while the ST effects decreased under further increasing the monomer ratio. Then, the divinyl benzene (DVB) was introduced to increase the cross-link density of the PS–AA. In comparison with the non-cross-link PS–AA nanospheres, the poly(styrene–acrylic acid–divinyl benzene) (PS–AA–DVB) based STFs exhibited much higher ST effects and the maximum viscosity was up to 385 Pa s when the DVB was only increased to 0.3%. In combination of the rheological properties and the structure characterization, a possible mechanism for the ST behavior was proposed and the influence of the particles’ characteristics on the mechanical performance of the PS–AA based STF was carefully analyzed.Graphical abstract

Novel asymmetric hollow microspheres with polystyrene-ethylacrylate (PSt-EA) semi-spherical cores and porous hierarchical Ni-Silicate shells have been successfully fabricated by the combination of emulsifier-free polymerization, a modified Stöber method and an in situ hydrothermal conversion reaction. During the conversion of the PSt-EA@SiO2 core/shell microspheres to the asymmetric PSt-EA/Ni-Silicate composite, the spherical PSt-EA was melted within the hollow Ni-Silicate interior to form semi-microspheres. Upon further treating the asymmetric hollow microspheres by 500 °C calcination for 5 h, hierarchical Ni-Silicate hollow spheres were obtained. The BET area of the asymmetric hollow PSt-EA/Ni-Silicate microspheres was 58.9 m2 g−1 and the pore diameter was about 10–20 nm. The large porous nature of the products enable them be used as carriers for bio-molecules, and experiments indicated that the maximum adsorption ability of the asymmetric hollow microspheres could reach 8.2 μmol g−1 when the concentration of Cytochrome C was 200 mmol L¬1.

A novel black Plasticine™ was developed by dispersing iron microparticles into the paraffin wax–petroleum jelly composite matrix. Due to the presence of magnetic particles, this Plasticine™ exhibited magnetic-dependent mechanical properties and can be defined as a typical magnetorheological gel (MRG) material. The magnetic Plasticines™ were malleable and their mechanical properties were highly influenced by the iron contents. With increasing of the externally applied magnetic field, the shear storage modulus sharply increased. Under the optimum iron content, the magnetic induced modulus can be increased to as high as 4.23 MPa, whereas the relative magnetorheological effect was 305% and this value was higher than the reported magnetorheological elastomer (MRE). Interestingly, when the temperature reached a critical point, the magnetic Plasticine™ changed to a fluid like material which exhibited the typical characteristics of magnetorheological fluid (MRF). It was found the versatile magnetic Plasticine™ can seldom be transformed between the MRG and MRF without changing its dynamic properties.

Superparamagnetic Ag@Fe3O4 nanospheres with core–shell nanostructures have been prepared by a facile one-pot method. The diameter of the as-synthesized nanospheres was about 200 nm and the core sizes were between 50 and 100 nm. By varying the concentrations, particles with tunable core size and total size are successfully achieved. Time dependent experiments were constructed to investigate the synthesis mechanism, which indicated that the present method corresponded to an Ostwald ripening progress. The BET area of the core–shell nanospheres is about 22.6 m2/g and this result indicates that the product shows a porous character. The saturated magnetization of the superparamagnetic Ag@Fe3O4 nanospheres is 27.4 emu g−1 at room temperature, which enables them to be recycled from the solution by simply applying a small magnet. Due to the unique nanostructure, these particles show high performance in catalytic reduction of 4-nitrophenol and can be used as reusable nanocatalysts.

A Fe3O4/Ag composite, with high efficiency in the degradation of rhodamine B was synthesized through a simple sonochemical method. These composites were obtained from sonication of Ag(NH3)2+ and (3-aminopropyl)triethoxysilane (APTES)-coated Fe3O4 nanoparticles solution at room temperature in ambient air for 1 h. A formation mechanism was proposed and discussed. This sonochemical method is attractive since it eliminated the use of any reductants, which is necessary to transform the Ag+ to the Ag0. In comparison to high temperature or high pressure experimental processes, this method is mild, inexpensive, green and efficient. The M–H hysteresis loop of these Fe3O4/Ag composite microspheres indicates that the composite spheres exhibit superparamagnetic characteristics at room temperature. Furthermore, these composites can be recycled six times by magnetic separation without major loss of activity. Thus, these Fe3O4/Ag composites can be served as effective and convenient recyclable catalysts for practical application.Research highlights▶ A Fe3O4/Ag composite, with high efficiency in the degradation of rhodamine B was synthesized through a simple sonochemical method. ▶ This sonochemical method is attractive since it eliminated the use of any reductant, which is needed to transform the Ag+ to the Ag0. Furthermore, the sonochemical preparation was accomplished at low temperature for short time. Compared with high temperature or high pressure experimental processes, it is found to be mild, inexpensive, green and efficient. ▶ Fe3O4/Ag composites exhibit excellent superparamagnetic characteristics. So Fe3O4/Ag catalyst can be rapidly gathered for recycling. ▶ Fe3O4/Ag composites can be recycled six times by magnetic separation without major loss of activity. It can be used as convenient and efficient recyclable catalysts. Moreover, this effective approach is expected to be used as attractive alternative to prepare other composites with tailored and unique properties.

The rheological behavior of polymethylmethacrylate (PMMA) particles suspensions in glycerine–water mixtures has been investigated by means of steady and dynamic rheometry in this work. The shear rheology of these suspensions demonstrates a strong shear thickening behavior. The variations of shear viscosity with the volume fraction and ratios of glycerine to water are discussed. The effect of volume fraction can be qualitatively explained using a clustering mechanism, which attributes the phenomena to the formation of temporary, hydrodynamic clusters. The influence of interactions between glycerine–water mixtures and PMMA particles on shear thickening is investigated by varying the ratio of glycerine to water. In addition, the reversible and thixotropic properties of suspensions of PMMA dispersed in glycerine–water (3:1) mixtures are also investigated, and the results demonstrate the excellent reversible and thixotropic properties of PMMA particle suspensions.

In this paper, a novel nanoporous barium titanate (BaTiO3) crystalline powder was synthesized by using triblock poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) based systems (P-123) as the soft template via a sol–gel method and their structure-dependent electro rheological property was studied. The pore diameter and specific surface area of BaTiO3 were precisely controlled by varing the calcined temperature. The chemical composition, structure and surface morphology of BaTiO3 were characterized by X-ray diffraction (XRD), thermo gravimetric analysis (TGA), and nitrogen adsorption–desorption method, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The result revealed that the pore volume and specific surface area of BaTiO3 decreased with the increment of calcined temperature. The electro rheological fluids (ERFs) were obtained by dispersing BaTiO3 crystallites in silicon oil and three kinds ERFs were fabricated by using three kinds of BaTiO3 which were prepared under different calcined temperature (550, 600 and 900 °C) as the precursors. The behaviors of the ERFs were evaluated via a rotational rheometer fixed with electric field generator. The results showed that electro rheological effect was related to the pore volume and specific surface area of BaTiO3. Due to the distinct advantage of sol–gel method for preparing nanoporous BaTiO3 without contamination of the materials, the markedly low current destiny of the ERFs was obtained. The yield stress of ERFs with large specific surface area of BaTiO3 reached the maximum of 3 kPa, which is higher than that of ERFs using traditional pure BaTiO3 crystallites (lower than 1 kPa).

An ultrasonic irradiation method was applied to the sol/gel synthesis of the single-crystal cubic barium strontium titanate Ba1−xSrxTiO3 (0 ⩽ x ⩽ 0.2). The characteristics of the composites were examined by X-ray diffraction, thermogravimetric analysis, differential thermal analysis, transmission electron microscopy and high-resolution transmission microscopy. The diameters and lengths of typical resultant Ba0.8Sr0.2TiO3 are in the range of 70–100 nm and 650–1000 nm, respectively. In addition, the stoichiometric sonogel formation and its heat-treatment process, the relationship between x of Ba1−xSrxTiO 3 and the crystal structure, the relationship between synthesis condition of sonogel and morphology have been discussed.

A novel black Plasticine™ was developed by dispersing iron microparticles into the paraffin wax–petroleum jelly composite matrix. Due to the presence of magnetic particles, this Plasticine™ exhibited magnetic-dependent mechanical properties and can be defined as a typical magnetorheological gel (MRG) material. The magnetic Plasticines™ were malleable and their mechanical properties were highly influenced by the iron contents. With increasing of the externally applied magnetic field, the shear storage modulus sharply increased. Under the optimum iron content, the magnetic induced modulus can be increased to as high as 4.23 MPa, whereas the relative magnetorheological effect was 305% and this value was higher than the reported magnetorheological elastomer (MRE). Interestingly, when the temperature reached a critical point, the magnetic Plasticine™ changed to a fluid like material which exhibited the typical characteristics of magnetorheological fluid (MRF). It was found the versatile magnetic Plasticine™ can seldom be transformed between the MRG and MRF without changing its dynamic properties.

A novel multi-functional polymer composite (MPC) with both excellent shear stiffening (ST) performance and magnetorheological (MR) effect is prepared by dispersing magnetic particles into shear stiffening polymer matrix. Besides having the magnetically dependent mechanical properties (MR effects), this multi-functional MPC automatically changes its rheological behavior in response to external shear stimuli. The mechanical properties of this smart composite can be alternatively achieved by varying the particle's types and contents. Upon applying a shear stress with excitation frequency from 1 Hz to 100 Hz, the storage modulus (G′) of the MPC increases from 102 to 106 Pa, demonstrating an excellent ST effect. Interestingly, the ST effects of the MPC are also tunable by varying the external magnetic field, and the area of G′ could be greatly increased and precisely controlled. Based on the experimental results, a possible mechanism is proposed and discussed. It is believed that the “cross bonds” and the particle chains induced by the magnetic field are due to the excellent multi-functional stimulus-response properties.

Novel asymmetric hollow microspheres with polystyrene-ethylacrylate (PSt-EA) semi-spherical cores and porous hierarchical Ni-Silicate shells have been successfully fabricated by the combination of emulsifier-free polymerization, a modified Stöber method and an in situ hydrothermal conversion reaction. During the conversion of the PSt-EA@SiO2 core/shell microspheres to the asymmetric PSt-EA/Ni-Silicate composite, the spherical PSt-EA was melted within the hollow Ni-Silicate interior to form semi-microspheres. Upon further treating the asymmetric hollow microspheres by 500 °C calcination for 5 h, hierarchical Ni-Silicate hollow spheres were obtained. The BET area of the asymmetric hollow PSt-EA/Ni-Silicate microspheres was 58.9 m2 g−1 and the pore diameter was about 10–20 nm. The large porous nature of the products enable them be used as carriers for bio-molecules, and experiments indicated that the maximum adsorption ability of the asymmetric hollow microspheres could reach 8.2 μmol g−1 when the concentration of Cytochrome C was 200 mmol L¬1.

A novel rate-dependent and self-healing conductive composite with a well-defined shear stiffening (S-ST) effect was facilely fabricated by dispersing multi-walled carbon nanotubes (MWCNTs) into a shear stiffening polymer matrix. The storage modulus (G′) of the multi-functional composite automatically increased 4 orders of magnitude when encountering external shear stimuli and the G′max was over 1 MPa, demonstrating an obvious shear stiffening effect and good safe-guarding performance. It was found that the electrical conductivity changed accordingly when shear stiffening occurred, therefore it can be applied as a force sensor during the attacking process. The rate-dependent piezoresistance effect of the composite was investigated. In quasi-static compression and high rate impact tests, different force signals can be obtained because of the negative and positive piezoresistivity effect. Self-healing tests indicated that the as-prepared composite can maintain its mechanical and electrical properties after destruction and healing treatments. Owing to the shear stiffening performance, the rate dependent conductive composite could both absorb impact energy and sense the attacking forces. Finally, a mechanism was proposed and it was believed that the glass transition induced by B–O interactions and the changes in the microstructure during the external action can be attributed to the S-ST performance and rate dependent electrical conductivity, respectively.

Superparamagnetic Ag@Fe3O4 nanospheres with core–shell nanostructures have been prepared by a facile one-pot method. The diameter of the as-synthesized nanospheres was about 200 nm and the core sizes were between 50 and 100 nm. By varying the concentrations, particles with tunable core size and total size are successfully achieved. Time dependent experiments were constructed to investigate the synthesis mechanism, which indicated that the present method corresponded to an Ostwald ripening progress. The BET area of the core–shell nanospheres is about 22.6 m2/g and this result indicates that the product shows a porous character. The saturated magnetization of the superparamagnetic Ag@Fe3O4 nanospheres is 27.4 emu g−1 at room temperature, which enables them to be recycled from the solution by simply applying a small magnet. Due to the unique nanostructure, these particles show high performance in catalytic reduction of 4-nitrophenol and can be used as reusable nanocatalysts.

A novel rod-like β-FeOOH@poly(dopamine)–Au–poly(dopamine) nanocomposite is developed for recyclable catalysis. Firstly, the rod-like β-FeOOH template was coated in situ by a layer of poly(dopamine) (PDA) to form a core/shell nanostructure. Then the negatively charged Au nanocatalysts were well-immobilized onto the periphery of the β-FeOOH@PDA nanorod. To protect the Au nanocrystals from leaching during the catalytic reactions, another PDA layer was coated onto the above particles to form a sandwich-like PDA–Au–PDA shell on the β-FeOOH rod core. The reduction of Rhodamine B (RhB) was introduced as a model reaction to evaluate the catalytic activity of the as-prepared nanocomposites. It was found that the catalytic rate sharply increased with an increasing amount of the nanocatalyst. Benefitting from the thin outer layer of PDA, the recyclability of the nanocatalyst dramatically increased. After five times of catalytic reaction, the activity was maintained as high as 98.3%, while the β-FeOOH@PDA–Au showed it to be retained at only 73.4%.