Haian Xie

Fluxible Nanoclusters of Fe3O4 Nanocrystal-Embedded Polyaniline by Macromolecule-Induced Self-Assembly

We have prepared Fe3O4 nanocrystal-embedded polyaniline hybrids with well-defined cluster-like morphology through macromolecule-induced self-assembly. These magnetic and electrically conductive composite nanoclusters show flowability at room temperature in the absence of any solvent, which offers great potential in applications such as microwave absorbents and electromagnetic shielding coatings. This macromolecule-induced self-assembly strategy can be readily applied on the fabrication of other ion oxide/conjugated polymer composites to achieve robust multifunctional materials.

Particle Size Dependence of the Dielectric Properties of Polyvinyledene Fluoride/Silver Composites

The dependence of the dielectric properties of micro- (m-) and nano- (n-) silver (Ag)/poly(vinylidene fluoride) (PVDF) composites on the Ag particle size was determined. The magnitude of dielectric constant and conductivity for the PVDF/n-Ag composites was much higher than that of the PVDF/m-Ag composites at the same Ag volume loading. Our results suggest that the percolative behaviors were quite different for the m- and n-systems owing to the Ag particle size effect. The dielectric property depends on the synergistic effects of interfacial area, interparticle distance, and interfacial adhesion, all of which are highly dependent on the Ag particle size. The increased interfacial area, reduced interparticle distance, and improved interfacial adhesion contributed to the better dielectric properties of the PVDF/n-Ag composites.

Self-Suspended Polyaniline Doped with a Protonic Acid Containing a Polyethylene Glycol Segment

Self-suspended nanoparticles (NPs) are flowable at or near room temperature without the presence of any solvent. The zero vapor pressure of self-suspended NPs eliminates the environmental concerns associated with using various solvents, and has attracted extensive research interests recently. Various hybrid self-suspended NPs have been synthesized from surface modification of the nanostructures, for example, SiO2, g-Fe2O3, [1,2] TiO2, [3] ZnO, quantum dots, gold, platinum, palladium, CaCO3, [7] and carbon nanotubes. The intrinsic electronic, magnetic, and luminescent properties of various nanostructures have made the self-suspended NPs a promising alternative to conducting lubricants, heat-transfer fluids, batteries, and printing electronics. Aside from the above mentioned self-suspended NPs and their corresponding liquid-like behavior, herein we report a self-suspended polyaniline (PANI) that exhibits a unique thermoreversible gel-like rheological response. Owing to the intrinsic electrical properties of PANI, the self-suspended PANI might exhibit high electroconductivity, excellent electroluminescence, unique electrochromism, and outstanding processability, which could have widespread application in electrochromic devices, medical diagnostic transducers, lightweight batteries, electroluminescent devices, fuel cells, sensors, and actuators. We anticipate that the technique reported here is also applicable to other polymers for exhibiting this unique structure and properties. The self-suspended PANI was prepared using a long-chain protonic acid containing a polyethylene glycol segment (CH3 ACHTUNGTRENNUNG(CH2)8-C6H4 ACHTUNGTRENNUNG(OCH2CH2)10OCH2CH2CH2SO3H) (NPES) as the dopant during the polymerization of the aniline monomers, and then removed the excess of NPES in the polymer solution through extensive dialysis. A dialysis experiment was carried out to investigate the removal of NPES, and the result indicates that all the unreacted NPES molecules can be extracted out of the dialysis bag (see the Supporting Information, Figure S1), which resulted in a solvent-free system. The doped PANI derivatives can self-assemble into nanofibrils. By controlling the average doping ratio of the PANI molecule chain within a system, the PANI nanofibrils can further organize into micelles and exhibit unique thermoreversible gel-like rheology behavior. Although such thermoreversible rheology behavior resembles those of previously reported thermoreversible gels, the two categories are essentially different in that a real thermoreversible gel possesses a fibrillar network morphology. The micelle morphology may originate from the nature of NPES which is quite different from those used in previously reported work involving sulfonic acid doped PANI; for example, NPES contains a long flexible chain segment of polyethylene glycol. These NPES molecules with high flexibility significantly alter the assembly behavior of doped PANI and thus results in PANI derivatives with unexpected properties. The doping ratio of NPES to PANI is represented by the average weight fraction of NPES, fNPES. PANI can exist in a variety of forms which differ in their oxidation state and consist of the reduced unit and the oxidized unit (see the Supporting Information, Figure S2). The reduced unit and the oxidized unit are present in a 1:1 ratio for the as-synthesized PANI molecule because a 1:1 molar ratio of aniline/ ammonium peroxydisulphate is used in the polymerization reaction. Therefore, every two nitrogen atoms in the assynthesized PANI molecule can only be doped by one [a] Dr. J. Huang, Dr. Q. Li, Y. Wang, Y. Wang, Prof. Dr. L. Dong, Dr. H. Xie, Prof. Dr. C. Xiong State Key Laboratory of Advanced Technology for Materials Synthesis and Processing and School of Materials Science and Engineering Wuhan University of Technology Wuhan 430070 (People s Republic of China) Fax: (+86) 27-8765-2879 E-mail : qili@live.whut.edu.cn [b] Prof. Dr. C. Xiong School of Materials Science and Engineering Wuhan Textile University Wuhan 430073 (People s Republic of China) E-mail : cxx@live.whut.edu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201100437.

Enhancement of Polymer Foam Quality by Modifying Structural and Decomposition Characteristics of Chemical Blowing Agent

The polymer foam quality was enhanced significantly by modifying the structural and decomposition characteristics of chemical blowing agent (CBA), including the basic particle size, compatibility with the polymer matrix and gas yield. The submicrometer semicarbazide-covalently anchored polystyrene (SCPS) particles were synthesized and utilized as a blowing agent for polystyrene foaming. The results demonstrated the decreased basic particle size, enhanced dispersion and modified decomposition characteristic of SCPS improved significantly the foam quality. The SCPS having homogeneous size distribution and good compatibility with the polymer matrix contributed to the uniform dispersion of CBA and thus confined cell coarsening.

Structure–Property Relationship in Injection-Molded Polypropylene/Clay Composite Foams

Polypropylene (PP)/organically modified montmorillonite (OMMT) composite foams were fabricated by a two-step injection foaming technique. The structure–mechanical property relationship in the composite foams was investigated. The OMMT favors the tensile and impact properties of the composite foams by optimizing the cell structure and the polymer matrix structure. The microcells in the polymer matrix played a positive part in the toughening of PP/OMMT composite foams, but lowered the reinforcing effect of OMMT as expected from the mixture rule. The enhanced mechanical properties for the composite foams were obtained by incorporating well-dispersed OMMT into PP matrix.

Self-assembled long-chain organic ion grafted carbon dot ionic nanohybrids with liquid-like behavior and dual luminescence

Ionic nanohybrids comprised of flexible long-chain organic ion coated luminous carbon dots are prepared via a rapid extraction method, demonstrating liquid-like behavior at ambient temperature in the absence of any solvents. In addition to their interesting dual luminescence behavior, this novel hybrid material holds great promise for a diverse array of fluorescence-based applications.

Water Dispersible Graphene Sheets Produced from Unassembled Graphene–Polyaniline Nanohybrids

We present an efficient process for producing water dispersible graphene sheets from unassembled graphene–polyaniline nanohybrids. The result of atomic force microscopy reveals that over 80% of thus-prepared graphitic sheets are single layers with typical thickness of approximately 0.8 nm. The proportion of modifying molecules in the product is found to be as low as 3.0 wt.%, as determined by elemental analysis. Along with its fascinating water dispersibility and remarkably high electrical conductivity, such material is anticipated to be very promising for use in graphene-based nanoelectronics and high-performance composites.