Shishan Wu

POLYMER/SILICA NANOCOMPOSITES: PREPARATION, CHARACTERIZATION, PROPERTIES, AND APPLICATIONS

5. In Situ Polymerization 3907 5.1. General Polymerization 3907 5.2. Photopolymerization 3910 5.3. Surface-Initiated Polymerization 3912 5.4. Other Methods 3913 6. Colloidal Nanocomposites 3913 6.1. Sol-Gel Process 3914 6.2. In Situ Polymerization 3916 6.2.1. Emulsion Polymerization 3917 6.2.2. Emulsifier-Free Emulsion Polymerization 3919 6.2.3. Miniemulsion Polymerization 3920 6.2.4. Dispersion Polymerization 3921 6.2.5. Other Polymerization Methods 3923 6.2.6. Conducting Nanocomposites 3924 6.3. Self Assembly 3926 7. Other Preparative Methods 3926 8. Characterization and Properties 3928 8.1. Chemical Structure 3928 8.2. Microstructure and Morphology 3929 8.3. Mechanical Properties 3933 8.3.1. Tensile, Impact, and Flexural Properties 3933 8.3.2. Hardness 3936 8.3.3. Fracture Toughness 3937 8.3.4. Friction and Wear Properties 3937 8.4. Thermal Properties 3938 8.5. Flame-Retardant Properties 3941 8.6. Optical Properties 3942 8.7. Gas Transport Properties 3943 8.8. Rheological Properties 3945 8.9. Electrical Properties 3945 8.10. Other Characterization Techniques 3946 9. Applications 3947 9.1. Coatings 3947 9.2. Proton Exchange Membranes 3948 9.3. Pervaporation Membranes 3948 9.4. Encapsulation of Organic Light-Emitting Devices 3948

Grafting of Zwitterion from Cellulose Membranes via ATRP for Improving Blood Compatibility

A p-vinylbenzyl sulfobetaine was grafted from cellulose membrane (CM) using surface-initiated atom transfer radical polymerization for blood compatibility improvement. Surface structure, wettability, morphology, and thermal stability of the CM substrates before and after modification were characterized by attenuated total reflectance Fourier transform infrared spectra, X-ray photoelectron spectroscopy measurement, water contact angle measurement, atomic force microscopy, and thermogravimetric analysis, respectively. The results showed that zwitterionic brushes were successfully fabricated on the CM surfaces, and the content of the grafted layer increased gradually with the polymerization time. The blood compatibility of the CM substrates was evaluated by protein adsorption tests and platelet adhesion tests in vitro. It was found that all the CMs functionalized with zwitterionic brush showed improved resistance to nonspecific protein adsorption and platelet adhesion, even though the grafting polymerization was conducted for several minutes.

Effect of the length of the side chains of comb-like copolymer dispersants on dispersion and rheological properties of concentrated cement suspensions.

Two different groups of comb-like copolymer dispersants with side chain lengths ranging from 8 to 48 were synthesized and characterized: one group with the carboxylic content per mole molecule constant and the other group with the carboxylic contents per gram polymer constant. The effects of side chain length on comb-like copolymers on adsorption, dispersion, rheological behavior, and zeta potential for cement suspensions were investigated systematically to elucidate the governing dispersing mechanism. The adsorption of comb-like copolymer on the cement surfaces, controlled by COO(-) content in copolymer backbones, side chain length, and also polymer conformation in solution, governs the dispersion and rheological behavior of the cementitious system. The dispersion effect increases with the adsorbed amount; especially the adsorbed side chain density increases. But the dispersion power of comb-like copolymers varies depending on the side chain length in comb-like copolymer. The long side chain polymer has higher dispersion power than the shorter ones due to the stronger steric hindrance effect of the former; for the short side chain polymer with high ionic content, the electrostatic repulsion and steric hindrance together should be responsible for its dispersion effect. Such information also suggests that their exists the geometrical balance between the main chain and the side chains in comb-like copolymer dispersants which should be very useful in designing optimum molecular structures of high efficient dispersants.

Dopamine fluorescent sensors based on polypyrrole/graphene quantum dots core/shell hybrids.

A facilely prepared fluorescent sensor was developed for dopamine (DA) detection with high sensitivity and selectivity based on polypyrrole/graphene quantum dots (PPy/GQDs) core/shell hybrids. The composites exhibit strong fluorescence emission, which is dramatically enhanced as high as three times than pristine GQDs. The prepared sensor allows a highly sensitive determination of DA by fluorescent intensity decreasing with the addition of DA and presents a good linearity in range of 5-8000 nM with the detection limit of 10 pM (S/N = 3). Furthermore, the application of the proposed approach have been demonstrated in real samples and showed promise in diagnostic purposes.

Ultrasensitive dopamine sensor based on novel molecularly imprinted polypyrrole coated carbon nanotubes

A novel electrochemical sensor using the molecularly imprinted (MIP) oxygen-containing polypyrrole (PPy) decorated carbon nanotubes (CNTs) composite was proposed for in vivo detection of dopamine (DA). The prepared sensor exhibits a remarkable sensitivity of (16.18μA/μM) with a linear range of 5.0×10(-11)-5.0×10(-6)M and limit of detection as low as 1.0×10(-11)M in the detection of DA, which might be due to the plenty cavities for binding DA through π-π stacking between aromatic rings and hydrogen bonds between amino groups of DA and oxygen-containing groups of the novel PPy.

Bamboo-like Composites of V2O5/Polyindole and Activated Carbon Cloth as Electrodes for All-Solid-State Flexible Asymmetric Supercapacitors.

A bamboo-like nanomaterial composed of V2O5/polyindole (V2O5/PIn) decorated onto the activated carbon cloth was fabricated for supercapacitors. The PIn could effectively enhance the electronic conductivity and prevent the dissolution of vanadium. And the activation of carbon cloth with functional groups is conducive to anchoring the V2O5 and improving surface area, which results in an enhancement of electrochemical performance and leads to a high specific capacitance of 535.5 F/g. Moreover, an asymmetric flexible supercapacitor based on V2O5/PIn@activate carbon cloth and reduced graphene oxide (rGO)@activate carbon cloth exhibits a high energy density (38.7 W h/kg) at a power density of 900 W/kg and good cyclic stability (capacitance retention of 91.1% after 5000 cycles). And the prepared device is shown to power the light-emitting diode bulbs efficiently.

A facilely prepared polypyrrole–reduced graphene oxide composite with a crumpled surface for high performance supercapacitor electrodes

A polypyrrole–reduced graphite oxide core–shell composite was facilely fabricated through electrostatic interactions and π–π accumulation. This novel composite shows remarkable performance as an electrode material for supercapacitors, with a high specific capacitance of 557 F g−1 at a current density of 0.5 A g−1, and retains a high value after 1000 charge–discharge processes. The maximum energy density of the fabricated supercapacitor based on the mass of active electrodes is calculated to be 49.5 W h kg−1 and 33.3 W h kg−1 at a power density of 0.22 kW kg−1 and 6.06 kW kg−1, the improved capacitance might be mainly ascribed to higher conductivity and more crumpled surface of the composite.

All-solid-state flexible supercapacitors based on highly dispersed polypyrrole nanowire and reduced graphene oxide composites.

Highly dispersed polypyrrole nanowires are decorated on reduced graphene oxide sheets using a facile in situ synthesis route. The prepared composites exhibit high dispersibility, large effective surface area, and high electric conductivity. All-solid-state flexible supercapacitors are assembled based on the prepared composites, which show excellent electrochemical performances with a specific capacitance of 434.7 F g(-1) at a current density of 1 A g(-1). The as-fabricated supercapacitor also exhibits excellent cycling stability (88.1% capacitance retention after 5000 cycles) and exceptional mechanical flexibility. In addition, outstanding power and energy densities were obtained, demonstrating the significant potential of prepared material for flexible and portable energy storage devices.

Adsorption Mechanism of Comb Polymer Dispersants at the Cement/Water Interface

Comb polymers are commonly used as dispersants to stabilize highly concentrated cement suspensions. The effectiveness of such polymeric additives to stabilize these suspensions is determined to a large extent by the amount adsorbed. In this study we investigated the adsorption characteristics of various comb dispersant containing different graft densities on surfaces of cement particle. The effect of inorganic salts on their adsorption was also examined in order to elucidate their adsorption mechanism. The results show that the adsorption of comb polymer dispersants on cement surface conforms approximately to Langmuirs adsorption isotherm and the characteristic plateau A s and adsorption free energy ΔGads are largely dependent on the anionic group content of the comb polymers. The A s and ΔGads increase with increasing anionic group content. This information suggests that the adsorption of comb polymers on cement surfaces is dominated by electrostatic interaction between COO-groups on the comb polymers and the positive surface of the cement. This conclusion is supported by effects of inorganics such as calcium and sulfate ions, and diffuse reflectance FTIR spectroscopy. The implication of results for tuning polymers for the required performance in cement manufacture should be noted.

Highly dispersed carbon nanotube/polypyrrole core/shell composites with improved electrochemical capacitive performance

Highly dispersed polypyrrole (PPy) is firstly designed for decorating onto the surface of pristine multiwalled carbon nanotubes (CNTs), then used in the facile synthesis of a CNT/PPy core/shell composite, which provides a potential application for further modification as a base-material due to its high dispersibility. The hybrid material with a PPy shell thickness of 1.61 nm displayed a high specific capacitance of 276.3 F g−1 in 1 M KCl electrolyte, four times higher than pristine CNT. Such an improvement in performance is closely correlated with the integrated advantage of the decorated PPy shell, which enhanced the dispersibility and active surface area.