Zhengdong Fei

Self-assembly of NiO nanoparticles in lignin-derived mesoporous carbons for supercapacitor applications

We demonstrate the self-assembly of highly dispersed NiO nanoparticles embedded in lignin-derived mesoporous carbon (MPC) frameworks. Self-assembly is induced by evaporation of the solvent from a mixture of metal-containing liquid crystalline mesophases of lignin-derived polymers and transition metal nitrate hydrate, which yielded NiO@MPC nanostructures at 600 °C under a N2 atmosphere. The microstructure and morphology of the NiO@MPC are characterized by XRD, TEM and BET. The results show that the NiO nanoparticles are highly dispersed in a mesoporous carbon matrix. The NiO@MPC composites show metal oxide contents in the range 49–79 wt%, high surface areas (503–802 m2 g−1), uniform pore sizes (≈3.7 nm), various porous distributions and large pore volumes (0.46–0.68 cm3 g−1). Electrochemical studies were carried out by measurement of cyclic voltammetry (CV) and charge–discharge tests. The results demonstrate that the NiO@MPC composites have high specific capacitance (880.2 F g−1 at a current density of 1.0 A g−1) and display good retention. 90.9% of the specific capacitance is retained when the current density changes from 1 A g−1 to 10 A g−1 in the charge–discharge tests and 93.7% of the specific capacitance is retained after 1000 charge–discharge cycles. Thus, the NiO@MPC composites are promising supercapacitor electrode materials.

Self-assembly between graphene sheets and cationic poly(methyl methacrylate) (PMMA) particles: preparation and characterization of PMMA/graphene composites

In this study, we presented a simple approach to prepare poly(methyl methacrylate) (PMMA)/graphene composites based on the self-assembly between graphene oxide (GO) sheets and cationic PMMA emulsion particles. Briefly, cationic PMMA emulsion particles were first synthesized by a soap-free emulsion polymerization process, in which methacryloyloxyethyl trimethyl ammonium chloride was used as the emulsifier, and then blended with the aqueous solution of GO. Through electrostatic attraction, the exfoliated GO sheets were tightly adhered on the PMMA particles. The GO sheets could be reduced in situ into graphene sheets by a chemical method, without the aggregation. The structure of the prepared composites and the influences of GO and graphene sheets on the properties of PMMA were investigated. Both GO and graphene sheets can increase the glass transition temperature and storage modulus of PMMA. Moreover, graphene sheets provided a more significant reinforcement effect.

Effect of nanoporous structure and polymer brushes on the ionic conductivity of poly(methacrylic acid)/anode aluminum oxide hybrid membranes

Anode aluminum oxide (AAO) porous materials have been widely used in ionic translocation for many biological and chemical studies. However, the lack of stimuli-response of this material limits its applications for the precise control of ionic transportation by the external environment. In this study, we functionalized the internal nanopores of AAO membranes to generate polyelectrolyte-filled pH-responsive membranes whose ionic conductivity could be readily controlled by changing the pH value. AAO membranes with different pore sizes (25, 75 and 100 nm) were modified with poly(methacrylic acid) (PMAA) by a “grafting-to” approach. Thermogravimetric and SEM analysis revealed that the extent of PMAA infiltration strongly depends upon the relative sizes of the nanopores and the PMAA concentration. Increasing the size of the nanopores enables the infiltration of PAA solution with a higher concentration. Electrochemical impedance spectroscopy demonstrated that the membrane conductivity decreases from 7.87 × 10−4 S cm−1 at pH 1 to 5.72 × 10−5 S cm−1 at pH 7. The functionalized AAO nanopores showed significant sensitivity to pH value, whereas a valve effect was observed in the pH range between 4 and 5. Our fabricated PMAA-AAO membranes show promising potential to be used as pH sensors and smart valves in micro-/nano-total analysis chips for biomedical and chemical applications.

Controlled Synthesis of Polyelectrolytes by 4-Cyanopentanoic Acid Dithiobenzoate Mediated RAFT Polymerization

We reported controlled synthesis of methacrylic acid, 2-(diethylamino) ethyl methacrylate and 2-acrylamido-2-methyl-1-propa- nesulfonic acid (three electrolyte-type monomers) via reversible addition-fragmentation chain transfer (RAFT) polymerization with the chain transfer agent (CTA) (4-cyanopentanoic acid)-4-dithiobenzoate and initiator (I) 4,4′-azobis(4-cyanovaleric acid) in homogeneous aqueous media. Three distinct [monomer]0: [I]0: [CTA]0 ratios (50:0.2:1, 100:0.2:1, 500:0.2:1) were conducted. The polymerizations exhibited the characteristics of a controlled/“living” polymerization which demonstrated well-controlled molecular weight and low molecular weight distribution. Finally, the results of this investigation were used as a guide for the preparation of a series of well-defined polyelectrolytes (DPn = 50–500, PDI = 1.08–1.17) in high yield.

Morphological Structure, Rheological Behavior, Mechanical Properties and Sound Insulation Performance of Thermoplastic Rubber Composites Reinforced by Different Inorganic Fillers

The application area of a sound insulation material is highly dependent on the technology adopted for its processing. In this study, thermoplastic rubber (TPR, polypropylene/ethylene propylene diene monomer) composites were simply prepared via an extrusion method. Two microscale particles, CaCO3 and hollow glass microspheres (HGW) were chosen to not only enhance the sound insulation but also reinforced the mechanical properties. Meanwhile, the processing capability of composites was confirmed. SEM images showed that the CaCO3 was uniformly dispersed in TPR matrix with ~3 μm scale aggregates, while the HGM was slightly aggregated to ~13 μm scale. The heterogeneous dispersion of micro-scale fillers strongly affected the sound transmission loss (STL) value of composites. The STL values of TPR composites with 40 wt % CaCO3 and 20 wt % HGM composites were about 12 dB and 7 dB higher than that of pure TPR sample, respectively. The improved sound insulation performances of the composites have been attributed to the enhanced reflection and dissipate sound energy in the heterogeneous composite. Moreover, the mechanical properties were also enhanced. The discontinued sound impedance and reinforced stiffness were considered as crucial for the sound insulation.

Enhanced sound insulation and mechanical properties based on inorganic fillers/thermoplastic elastomer composites

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 composite referred to polypropylene (PP) and the rubber phase was chosen by styrene butadiene styrene (SBS). SEM observation conformed that the inorganic particles were mainly dispersed in continuous PP phase and SBS phase remained in an isolated structure. The sound insulation property was measured by a four-microphone impedance tube. Compared to pure polymer sample, both CaCO3 and HGM-filled TPE composites exhibited greatly enhanced soundproof efficiency, which increased the sound transmission loss value from original 29 dB to 45 dB. The soundproof mechanism was investigated in detail. The damping of acoustic energy was contributed by the extended difference between the stiffness and acoustic impedance between plastic phase and rubber phase. The dispersion and property of inorganic fillers were considered as key factors to increase the dissipation of sound wave. Meanwhile, the mechanical properties of TPE composites were enhanced due to the addition of inorganic fillers.

Facile Preparation of Crosslinked PAN Membranes Based on Thiol-Ene Photopolymerization

To improve the mechanical strength and antipollution properties of membranes, this research presents a facile method to prepare crosslinked polyacrylonitrile (PAN) membranes. This was achieved firstly by radical copolymerization with acrylonitrile, allyl methacrylate and sulfobetaine methacrylamide. Then, the copolymer was crosslinked by a thiol-ene click reaction under UV irradiation. Finally, the crosslinked membranes were prepared by traditional immersion precipitation phase inversion. These prepared membranes showed excellent water-pressure resistance and solvent swelling, owing to their crosslinked structure. This research will help in preparing crosslinked membranes through facile crosslinking under mild reaction conditions. The betaine structure also considerably improved the antifouling properties of the membranes.