乳液聚合法制备聚苯胺/纳米石墨薄片/Eu3+纳米复合材料及其导电性能

与传统乳液聚合法不同,采用现场乳液聚合法,直接将纳米石墨薄片在超声条件下有机改性.将无机物的有机改性、对甲苯磺酸的掺杂及苯胺单体的聚合同步进行,即制得目标产物.通过红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)和热重(TG)对该复合材料进行了表征和分析.结果表明,聚苯胺成功插层到纳米石墨薄片中,并形成了纳米薄膜,Eu3 分散在纳米膜中.热重(TG)分析和电导率测试结果表明,复合材料的热稳定性和导电性均较纯聚苯胺高.     

Thermoelectric properties of graphene nanosheets-modified polyaniline hybrid nanocomposites by an in situ chemical polymerization

A hybrid material of polyaniline protonated with hydrochloric acid and conductive graphene nanosheets (PANi/GNs) has been prepared by an in situ chemical polymerization method. The interactions between PANi and GNs in the hybrid composites are investigated by utilizing XRD, FT-IR, UV–vis and Raman. It is found that the PANi are adsorbed on the surface of the GNs, and the morphology of PANi transforms from twist structure to extended structure after the GNs are introduced. The thermoelectric (TE) properties of PANi/GNs composites have been investigated in the range from 323 K to 453 K. The electrical conductivity and the Seebeck coefficient of PANi/GNs composites are obviously higher than those of the PANi, while the thermal conductivity of the composites still keeps relatively low values even with high GNs content, resulting in the increase in dimensionless figure of merit (ZT). A highest ZT value of 1.95 × 10⁻³ has been obtained for the composite containing 30 wt % GNs at 453 K, which is about 70 times higher than that obtained from the PANi.     

Electrical and mechanical properties of PMMA/reduced graphene oxide nanocomposites prepared via in situ polymerization

We report the effect of filler incorporation techniques on the electrical and mechanical properties of reduced graphene oxide (RGO)-filled poly(methyl methacrylate) (PMMA) nanocomposites. Composites were prepared by three different techniques, viz. in situ polymerisation of MMA monomer in presence of RGO, bulk polymerization of MMA in presence of PMMA beads/RGO and by in situ polymerization of MMA in presence of RGO followed by sheet casting. In particular, the effect of incorporation of varying amounts (i.e. ranging from 0.1 to 2 % w/w) of RGO on the electrical, thermal, morphological and mechanical properties of PMMA was investigated. The electrical conductivity was found to be critically dependent on the amount of RGO as well as on the method of its incorporation. The electrical conductivity of 2 wt% RGO-loaded PMMA composite was increased by factor of 10⁷, when composites were prepared by in situ polymerization of MMA in the presence of RGO and PMMA beads, whereas, 10⁸ times increase in conductivity was observed at the same RGO content when composites were prepared by casting method. FTIR and Raman spectra suggested the presence of chemical interactions between RGO and PMMA matrix, whereas XRD patterns, SEM and HRTEM studies show that among three methods, the sheet-casting method gives better exfoliation and dispersion of RGO sheets within PMMA matrix. The superior thermal, mechanical and electrical properties of composites prepared by sheet-casting method provided a facile and logical route towards ultimate target of utilizing maximum fraction of intrinsic properties of graphene sheets.     

原位聚合PA11/GO纳米复合材料的流变性能研究

采用原位聚合法制备了PA11(尼龙11)/GO(GO)纳米复合材料,并采用XLY-Ⅱ型毛细管流变仪研究了共混物的流变特性。结果表明:PA11及其复合材料均为假塑性流体,呈现切力变稀的现象;非牛顿指数n均小于1。随着GO含量的增加,PA11/GO纳米复合材料的表观黏度升高,粘流活化能下降,表明共混材料的表观黏度对温度的敏感性降低,易于加工成型。     

Hopping conduction on PPy/SiO2 nanocomposites obtained via in situ emulsion polymerization

This work describes the preparation and electrical characterization of conducting polypyrrole (PPy) and silica nanocomposites. Four samples were investigated: (i) pure PPy, (ii) PPy-covered SiO₂ spherical nanoparticles, (iii) PPy-covered SiO₂ spherical nanoparticles modified with 3-aminopropyltriethoxysilane (APS), and (iv) PPy-covered SiO₂ fibers. Structural characterization was made by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrical conductivity was measured from 80 K to 300 K and three-dimensional variable range hopping conduction was observed. From the hopping parameter the mean hopping distance was obtained as well as the density of active center and the energy associated with it.     

Graphene oxide reinforced polyimide nanocomposites via in situ polymerization

Graphene oxide (GO) reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers in the presence of GO sheets dispersed in N,N-Dimethylacetamide (DMAc). The functional groups (e.g., hydroxyl, epoxide, and carboxyl groups) associated with the GO make GO excellent dispersion in the organic solvent, which benefits the subsequent in situ polymerization. This process enabled uniform dispersion of GO sheets in the polymer matrix. The resultant GO-polyimide nanocomposite films were studied by tensile test, TGA and SEM. The results showed that the GO sheets incorporated in the polymer matrix exhibited a layer-aligned structure without destruction of the thermal stability of the polymer matrix, and a loading of GO (10 wt%) resulted in a significant enhancement in elastic modulus (86.4%).     

Highly conductive graphene oxide/polyaniline hybrid polymer nanocomposites with simultaneously improved mechanical properties

Graphene oxide (GO) was added to a polymer composites system consisting of surfactant-wrapped/doped polyaniline (PANI) and divinylbenzene (DVB). The nanocomposites were fabricated by a simple blending, ultrasonic dispersion and curing process. The new composites show higher conductivity (0.02–9.8 S/cm) than the other reported polymer system filled with PANI (10⁻⁹–10⁻¹ S/cm). With only 0.45 wt% loading of GO, at least 29% enhancement in electric conductivity and 29.8% increase in bending modulus of the composites were gained. Besides, thermal stability of the composites was also improved. UV–Vis spectroscopy, X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) revealed that addition of GO improves the dispersion of PANI in the polymer composite, which is the key to realize high conductivity.     

In situ synthesis of thermochemically reduced graphene oxide conducting nanocomposites

Highly conductive reduced graphene oxide (GO) polymer nanocomposites are synthesized by a well-organized in situ thermochemical synthesis technique. The surface functionalization of GO was carried out with aryl diazonium salt including 4-iodoaniline to form phenyl functionalized GO (I-Ph-GO). The thermochemically developed reduced GO (R-I-Ph-GO) has five times higher electrical conductivity (42,000 S/m) than typical reduced GO (R-GO). We also demonstrate a R-I-Ph-GO/polyimide (PI) composites having more than 10(4) times higher conductivity (~1 S/m) compared to a R-GO/PI composites. The electrical resistances of PI composites with R-I-Ph-GO were dramatically dropped under ~3% tensile strain. The R-I-Ph-GO/PI composites with electrically sensitive response caused by mechanical strain are expected to have broad implications for nanoelectromechanical systems.     

聚苯胺的乳液聚合研究进展

本文详细介绍了聚苯胺(PANI)乳液聚合和微乳液聚合两种聚合方法,并综述了近年来乳液聚合制备PANI研究进展.     

Morphology-controlled fabrication of sulfonated graphene/polyaniline nanocomposites by liquid/liquid interfacial polymerization and investigation of their electrochemical properties

A novel morphology-controlled strategy has been developed to fabricate sulfonated graphene/polyaniline (SGEP) nanocomposites by liquid/liquid interfacial polymerization. Sulfonated graphene (SGE) sheets were synthesized and used as both a macromolecular acid dopant and substrate for the polymerization of polyaniline (PANI), affording the SGEP nanocomposites. The morphology of PANI in the nanocomposites can be controlled to be either nanorods or nanogranules by varying the synthesis conditions. The morphology of SGEP and the shape of PANI can be tuned by adding an additional dopant and varying the amount of SGE used, and this had a significant influence on the electrochemical performance of the nanocomposites as supercapacitor electrode materials. The SGEP nanocomposite with PANI nanorods exhibited a specific capacitance of 763 F/g with a capacity retention of 96% after 100 cycles and good rate properties. Composites obtained with HCl as an additional acid dopant with two different ratios of SGE to PANI showed higher specific capacitances of 793 and 931 F/g, but lower capacity retention after 100 cycles of 77% and 76%, respectively.      

以氧化石墨烯为氧化介质制备石墨烯/聚苯胺导电复合材料

采用超声辅助Hummers法制得厚度约为1 nm的氧化石墨烯, 以其为氧化介质与苯胺反应合成了石墨烯/聚苯胺(RGO/PANI)导电复合材料。利用AFM、SEM、XRD和FTIR对反应所得产物进行了表征。结果表明: 苯胺在略高于室温的酸性水溶液中可以对氧化石墨烯(GO)进行还原, 而苯胺自身则被氧化石墨烯中大量的含氧基团氧化并发生聚合反应, 最终生成RGO/PANI导电复合材料, 当苯胺用量为1 mL, 氧化石墨烯用量为0.1 g, 在水浴温度为70 ℃下剧烈搅拌24 h时, 获得的RGO/PANI复合材料导电性最佳, 约为10 S/cm。     

In situ synthesis and thermal,tribological properties of thermosetting polyimide/graphene oxide nanocomposites

The full exfoliation graphene oxide (GO) nanosheets were synthesized by an improved Hummers’ method. The phenylethynyl terminated thermosetting polyimide (PI) and PI/GO nanocomposites were prepared via a polymerization of monomer reactants process. Thermogravimetric analysis indicated that the incorporation of GO increased the thermal stability of the PI at low filling content. The friction and wear testing results of the PI and PI/GO nanocomposites under dry sliding condition against GCr15 steel showed that the addition of GO evidently improved the friction and wear properties of PI, which were considered to be the result of the formation of uniform transfer film and the increasing of load-carrying capacity. The friction and wear properties of the PI and PI/GO nanocomposites were investigated on a model ring-on-block test rig under dry sliding conditions against the GCr15 steel. Experimental results showed that the addition of GO evidently improved the friction and wear properties of PI, which were considered to be the result of the formation of uniform transfer film and the increasing of load-carrying capacity. The optimum GO content of nanocomposite for tribological properties is 3 wt%, which could be a potential candidate for tribo-material under dry sliding condition against GCr15 steel.     

Fracture mechanisms in polystyrene/laponite nanocomposites prepared by emulsion polymerization

Transmission electron microscopy (TEM) has been used to investigate the effect of laponite clay on microdeformation in thin latex-based polystyrene (PS) films, in which the laponite was concentrated at the original interfaces between the PS particles. At room temperature, a transition was observed from crazing in pure PS to a coarser fibrillar deformation mode as the laponite content increased. Moreover, whereas pure PS showed increasingly homogeneous deformation as T approached T_g, the fibrillar deformation zones observed in the nanocomposites persisted up to T just below T_g, and there was some evidence for yielding behaviour at even higher T in the presence of laponite. The macroscopic fracture resistance of the films, as assessed from double edge-notched tensile specimens, initially increased with laponite content, but decreased for laponite contents greater than 5 wt% with respect to the styrene monomer. This was attributed to a decrease in local ductility, consistent with the observation of reduced deformation ratios in the deformation zones by TEM, and to the intrinsic weakness of the laponite stacks and/or the PS-laponite interface. Thus, specimens with laponite contents comparable with the estimated threshold for percolation of contacts between the laponite stacks showed extremely brittle behaviour, associated with crack propagation along the interfaces between the latex particles.     

Crystallization,mechanical performance and hydrolytic degradation of poly(butylene succinate)/graphene oxide nanocomposites obtained via in situ polymerization

Poly(butylene succinate) (PBS)/graphene oxide (GO) nanocomposites were fabricated via in situ polymerization with very low GO content (from 0.03 to 0.5 wt%). The microstructures of the nanocomposites were characterized with Raman spectroscopy, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), sedimentation experiments and atomic force microscopy (AFM). The results showed that PBS chains have been successfully grafted onto GO sheets during in-situ polymerization, accompanied by the thermo-reduction from GO to graphene. The grafted GO displayed a great nucleating effect on PBS crystallization, resulting in largely improved crystallization temperature and decreased spherules size. A simultaneous enhancement in tensile strength and elongation was achieved for PBS/GO nanocomposites fiber. Meanwhile, increase in hydrolytic degradation rate was also observed for these nanohybrids. Our result indicates that using very low content GO is a simple way to achieve good dispersion yet with remarkable property enhancement for polymer/GO nanocomposites.     

Straightforward synthesis of hyperbranched polymer/graphene nanocomposites from graphite oxide via in situ grafting from approach

The grafting of graphite oxide (GO) with cyclic ether monomers, directly affords grafting with hyperbranched polymers. The resulting nanocomposites show good solubility in the solvents of polymers, exfoliation of graphene in the polymer matrix and excellent mechanical properties and robustness under bending.