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Yang D.,Beijing Institute of Petrochemical Technology | Yang D.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Huang S.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Huang S.,Beijing University of Chemical Technology | And 12 more authors.
RSC Advances | Year: 2015

In order to improve compatibility between the dielectric filler and polymeric matrix, we used bio-inspired polydopamine (PDA) to modify titanium dioxide (TiO2) nano-particles. The PDA coated TiO2 (TiO2-PDA) nano-particles were incorporated into nitrile-butadiene rubber (NBR) which contains a large amount polar groups to obtain a dielectric elastomer composite with a large actuated strain under a low electric field. The relatively soft insulating PDA layer on the TiO2 nano-particles led to the composites filled with TiO2-PDA nano-particles displaying better filler dispersion, much lower elastic modulus, lower dielectric loss, and higher electric breakdown field compared with the composites filled with pristine TiO2 nano-particles, resulting in a high electromechanical sensitivity (β). At last, an actuated strain of 5.2% at a relatively safe electric field of 12.5 kV mm-1 without any pre-strains was obtained by the 10 phr TiO2-PDA/NBR composite, a 140% increase in actuated strain compared with the actuated strain (0.69%) of pure NBR at 20 kV mm-1 without any pre-strains. This biomimetic method is simple, efficient, nontoxic, and easy to control, which can be used in other dielectric fillers to improve electromechanical properties of dielectric elastomers. © 2015 The Royal Society of Chemistry.


Wu Y.-B.,Beijing Institute of Petrochemical Technology | Wu Y.-B.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Han L.,Beijing Institute of Petrochemical Technology | Han L.,Beijing Key Laboratory of Special Elastomeric Composite Materials | And 11 more authors.
Polymer Chemistry | Year: 2015

Cationic polymerization of isobutyl vinyl ether (IBVE) in an ionic liquid 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]) was thoroughly examined at 0°C. A variety of coinitiators were used in conjunction with the IBVE-HCl adduct acting as a cationogen. Compared with polymerization in organic solvents, the cationic polymerization of IBVE in [omim][BF4] proceeded in a milder exothermic manner, yielding polymers with higher molecular weight, and giving a higher monomer conversion. Although the polymerization reaction in [omim][BF4] could not be controlled due to the presence of β-proton elimination, the monomer addition experiments confirmed the existence of long-lived species. Introducing a small amount of 2,6-di-tert-butylpyridine (DTBP) into the system may lead to a controlled polymerization. The corresponding elementary reactions and stabilization mechanism of propagating the carbocation in [omim][BF4] were also proposed. This journal is © 2015 The Royal Society of Chemistry.


Yang D.,Beijing Institute of Petrochemical Technology | Yang D.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Huang S.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Huang S.,Beijing University of Chemical Technology | And 13 more authors.
RSC Advances | Year: 2015

Dielectric elastomers (DEs), which are capable of displaying considerable stress and strain in response to an applied electric field, have shown the closest similarity in performance to natural muscles. However, the high operating voltage of DEs limits their practical application. A reduction of the operating voltage can be achieved through increasing the dielectric constant and/or decreasing the elastic modulus. Here, an all-organic non-percolative dielectric composite with enhanced electromechanical actuating performance was prepared by introducing polyaniline (PANI) and epoxidized soybean oil (ESO) into a nitrile-butadiene rubber (NBR) matrix. A small amount of PANI was used to increase the dielectric constant through adding electron movement which is similar to dipole polarization, while ESO was used to decrease the elastic modulus of the composite through weakening intermolecular interactions in NBR and molecular interaction between NBR and PANI. Finally, an actuated strain of 2.5% was obtained at 4.5 V μm-1 by 4 phr PANI/NBR composite filled with 50 phr ESO, a 700% improvement in actuated strain compared with the actuated strain (0.31%) of pure NBR at 4.5 V μm-1 without any pre-strains. In comparison with other dielectric composites filled with conductive filler, the ESO/PANI/NBR composite also displays a relative advantage under conditions of no pre-strain and low electric field. © 2015 The Royal Society of Chemistry.


Yang D.,Beijing Institute of Petrochemical Technology | Yang D.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Ruan M.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Ruan M.,Beijing University of Chemical Technology | And 14 more authors.
Journal of Materials Chemistry C | Year: 2016

In order to obtain a nitrile-butadiene rubber (NBR) dielectric elastomer composite with excellent electromechanical properties, a combination of bio-inspired poly(dopamine) (PDA) deposition and γ-methacryloxypropyl trimethoxy silane (KH570) grafting was proposed to functionalize the surface of titanium dioxide (TiO2) nanoparticles. Inspired by adhesive proteins in mussels, dopamine self-polymerization was used to deposit a thin adherent PDA film onto the surface of TiO2. KH570 that contains double bonds was then grafted through the reactions with hydroxyl and indole groups of the PDA surface. The chemical structure and composition of the TiO2 surface were characterized by XPS, FTIR, and HR-TEM. Because of the introduction of PDA grafted with the KH570 layer, the NBR composites filled with modified TiO2 displayed better filler dispersion, higher dielectric constant, lower elastic modulus, and higher electric breakdown field compared with composites filled with pristine TiO2 particles. Finally, a large actuated strain of about 16% at 60 kV mm-1 without any pre-strains was shown by the composite of NBR filled with 20 phr modified TiO2 particles, which is 53% larger than that of NBR without a filler. The process was fast, simple, efficient, nontoxic, and controllable, which can provide a new universal method for modification of dielectric fillers to improve the dielectric properties and electromechanical properties of dielectric elastomers. © 2016 The Royal Society of Chemistry.


Yang D.,Beijing Institute of Petrochemical Technology | Yang D.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Ruan M.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Ruan M.,Beijing University of Chemical Technology | And 13 more authors.
RSC Advances | Year: 2016

In this study, a combination of bio-inspired poly(dopamine) (PDA) deposition and γ-methacryloxypropyl trimethoxy silane (KH570) grafting is proposed to functionalize the surface of barium titanate (BT) with the aim to improve the electromechanical properties of silicone dielectric elastomers. Inspired by the composition of adhesive proteins in mussels, we used dopamine self-polymerization to form a thin adherent PDA film onto the surface of BT. KH570, which contains double bonds, was then grafted through reactions with the hydroxyl and indole groups of the PDA surface. The surface composition and microstructure of the modified BT particles were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HR-TEM), and thermogravimetric analysis (TGA). The results show that PDA grafted with KH570 (denoted as PDA + KH570) was successfully coated on the BT particles. In addition, the PDA + KH570 layer containing double bonds not only improved the dispersion of the fillers in the polymer matrix but also helped in the formation of strong interfacial interactions between the BT particles and silicone elastomer matrix, which led to an improved dielectric constant and actuated strain. Finally, the tensile strength of all the silicone dielectric composites is larger than 5 MPa, which is much higher than commercial acrylic dielectric elastomers. This is a big advantage for the practical application of a dielectric elastomer. © 2016 The Royal Society of Chemistry.


Zhang X.,Beijing University of Chemical Technology | Zhang X.,Beijing Institute of Petrochemical Technology | Zhang X.,Beijing Key Laboratory of Special Elastomeric Composite Materials | Guo W.,Beijing University of Chemical Technology | And 19 more authors.
Polymer Chemistry | Year: 2016

Cationic polymerization of p-methylstyrene (p-MeSt) in imidazolium-based [NTf2 -1] ionic liquids (ILs) was investigated. The effects of the anions, cations, and alkyl chain length of ILs on p-MeSt solubility and viscosity were comprehensively studied. The COSMO-RS method, which is a valuable tool for screening and selecting ILs, was also applied to identify the most suitable solvent for p-MeSt cationic polymerization. The results revealed that p-MeSt cationic polymerization proceeded in a milder exothermic manner in ILs than in a traditional organic solvent. Controlled polymerizations were achieved in [Bmim][NTf2] with a CumOH/BF3OEt2 initiating system at -25 °C when 2,6-di-tert-butylpyridine was introduced. The cationic polymerization mechanism of p-MeSt in ILs was proposed on the basis of the results of density functional theory and the terminal structures of polymers. © 2016 The Royal Society of Chemistry.

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