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1.
Graphene nanosheets offer intriguing electronic, thermal, and mechanical properties and are expected to find a variety of applications in high‐performance nanocomposite materials. Dispersal of graphene nanosheets in polymer hosts and precise interface control are challenging due to their strong interlayer cohesive energy and surface inertia. Here, an efficient strategy is presented for growing polymers directly from the surface of reduced graphene oxide (GO). This method involves the covalent attachment of Br‐containing initiating groups onto the surface of hydrazine hydrate reduced GO via a diazonium addition and the succeeding linking of poly(tert‐butyl methacrylate) (PtBMA) chains (71.7 wt % grafting efficiency) via surface‐initiated single‐electron‐transfer living radical polymerization (SET‐LRP) to graphene nanosheets. The resulting materials were characterized by using a range of testing techniques and it was proved that polymer chains were successfully introduced to the surface of exfoliated graphene sheets. After grafting with PtBMA, the modified graphene sheets still maintained the separated single layers, and the dispersibility was improved significantly. The method is believed to offer possibilities for optimizing the processing properties and interface structure of graphene–polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.  相似文献   

2.
In this study, we report a mild and efficient strategy for growing thermosensitive polymers directly from the surface of exfoliated graphene oxide (GO). Exfoliated GO sheets were sequentially subject to the epoxide ring‐opening reaction with tris(hydroxymethyl) aminomethane (TRIS) to increase the amount of reactive sites, the esterification with 2‐bromo‐2‐methylpropionyl bromide to introduce the Br‐containing initiating groups, and the surface‐initiated single electron transfer–living radical polymerization of N‐isopropylacrylamide (NIPAM) to tune the molecular weights of grafted polymers. All these reactions were performed at ambient temperature without losing any other oxygen‐containing functionality on GO. The resulting TRIS‐GO‐PNIPAM nanocomposites still maintain the separated single layers in dispersion, and the dispersibilities in organic solvents are significantly improved. Meanwhile, the aqueous dispersion of TRIS‐GO‐PNIPAM shows reversible temperature switching self‐assembly and disassembly behavior at about 40°C. Such smart graphene‐based hybrid materials are promising for applications in nanoelectronics, sensors, and microfluidic switches. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

3.
A mild and efficient strategy is presented for growing thermo‐sensitive polymers directly from the surface of exfoliated graphene oxide (GO). This method involves the covalent attachment of Br‐containing initiating groups onto the surface of GO sheets followed by in situ growing poly[poly(ethylene glycol) ethyl ether methacrylate] (PPEGEEMA) via single‐electron‐transfer living radical polymerization (SET‐LRP). Considering the lack of reactive functional groups on the surface of GO, exfoliated GO sheets were subjected to an epoxide ring opening reaction with tris(hydroxymethyl) aminomethane (TRIS) at room temperature. The initiating groups were grafted onto TRIS‐GO sheets by treating hydroxyls with 2‐bromo‐2‐methylpropionyl bromide at room temperature. PPEGEEMA chains were synthesized by in situ SET‐LRP using CuBr/Me6TREN as catalytic system at 40 °C in H2O/THF. The resulting materials were characterized using a range of testing techniques and it was proved that polymer chains were successfully introduced to the surface of GO sheets. After grafting with PPEGEEMA, the modified GO sheets still maintained the separated single layers and the dispersibility was significantly improved. This TRIS‐GO‐PPEGEEMA hybrid material shows reversible self‐assembly and deassembly in water by switching temperature at about 34 °C. Such smart graphene‐based materials promise important potential applications in thermally responsive nanodevices and microfluidic switches. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

4.
Preparation and characterization of poly(N‐isopropylacrylamide) (PNIPAM) polymer brushes on the surfaces of reduced graphene oxide (RGO) sheets based on click chemistry and reversible addition‐fragmentation chain transfer (RAFT) polymerization was reported. RGO sheets prepared by thermal reduction were modified by diazonium salt of propargyl p‐aminobenzoate, and alkyne‐functionalized RGO sheets were obtained. RAFT chain transfer agent (CTA) was grafted to the surfaces of RGO sheets by click reaction. PNIPAM on RGO sheets was prepared by RAFT polymerization. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and transmission electron microscopy (TEM) results all demonstrated that RAFT CTA and PNIPAM were successfully produced on the surfaces of RGO sheets. Nanosized PNIPAM domains on RGO sheets were observed on TEM. Micro‐DSC result indicated that in aqueous solution PNIPAM on RGO sheets presented a lower critical solution temperature at 33.2 °C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

5.
A convenient and industrially scalable method for synthesis of homogeneous nanocomposite films comprising poly(styrene‐stat‐butyl acrylate) and nanodimensional graphene oxide (GO) or reduced GO (rGO) is presented. Importantly, the nanocomposite latex undergoes film formation at ambient temperature, thus alleviating any need for high temperature or high pressure methods such as compression molding. The method entails synthesis of an aqueous nanocomposite latex via miniemulsion copolymerization relying on nanodimensional GO sheets as sole surfactant, followed by ambient temperature film formation resulting in homogeneous film. For comparison, a similar latex obtained by physical mixing of a polymer latex with an aqueous GO dispersion results in severe phase separation, illustrating that the miniemulsion approach using GO as surfactant is key to obtaining homogeneous nanocomposite films. Finally, it is demonstrated that the GO sheets can be readily reduced to rGO in situ by heat treatment of the film. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2289–2297  相似文献   

6.
A new soluble donor‐acceptor type poly(N‐vinylcarbazole)‐covalently functionalized graphene oxide (GO‐PVK) has been synthesized by reaction of DDAT (S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐aceticacid)trithiocarbonate)‐PVK with GO‐toluene‐2,4‐diisocynate. The incorporation of sufficient amount of PVK chains makes the modified GO nanosheets readily dispersible in organic solvents. The resulting material exhibits an enhanced solubility of 10 mg/mL in organic solvents. Covalent grafting of PVK onto the edge and surface of GO nanosheets did not change the carbazole absorption in the ultraviolet region, but substantially reduced the absorption intensity of GO in the visible region. The intensity of the emission band of GO‐PVK at 437 nm was a little bit quenched when compared with that of DDAT‐PVK, suggesting intramolecular quenching from PVK to GO. Such intramolecular quenching process may involve energy or electron transfer between the excited singlet states of the PVK moiety and the GO moiety. The HOMO/LUMO values and the energy bandgap of GO‐PVK experimentally estimated by the onset of the redox potentials are ?5.60, ?3.58, and 2.02 eV, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2642–2649, 2010  相似文献   

7.
In the present study, cross-linked poly (dimethacrylate- urethane dimethacrylate) [poly (BisGMA-UDMA)] functionalized-graphene oxide nanosheets were prepared via single-electron transfer living radical polymerization (SET-LRP) using the ‘grafting from’ strategy, under mild conditions. This method first involves the covalent attachment of Br-containing groups onto the surface of grapheme sheets to give the initiating-groups-containing graphene (G-Br). After that, the succeeding SET-LRP polymerization in DMSO in the presence of a Cu wire/Me6TREN catalytic system at room temperature leads to the grafting of poly (BisGMA-UDMA) chains onto the graphene surface. The resulting graphene-poly (dimethacrylate- urethane dimethacrylate) (G-PDMA-UDMA) nanocomposites were characterized using FT-IR, XRD, DSC, AFM, FE-SEM, and TEM analysis techniques. It was proved that polymer chains were successfully introduced to the surface of the graphene planes. After grafting with poly (BisGMA-UDMA), the dispersibility of the modified GO sheets significantly improved. When compared to G-PDMA, the resulting G-PDMA-UDMA nanocomposite revealed around 75%, 97%, and 65%, increase in compressive strength, Young's modulus and toughness, respectively. Such smart graphene-based nanocomposites can be used as promising biomaterials in orthopaedic and dental applications with the desired mechanical properties.  相似文献   

8.
We herein report a “grafting from” strategy to immobilize optically active helical poly(phenyl isocyanide)s onto graphene oxide (GO) nanosheets. After covalently bounding alkyne‐Pd(II) initiator onto GO nanosheets, the designed GO/polymer composites P1 @GO and P1 ‐b‐ P2 @GO featuring single‐handed helical poly(phenyl isocyanide)s growing from GO nanosheets were prepared by sequential addition of the chiral and achiral isocyanide monomers. Post‐synthetic hydrolysis rendered P1 ‐b‐ P3 @GO to improve the hydrophilicity. The successful covalent bonding of poly(phenyl isocyanide)s chains onto GO nanosheets was certified by several cross evidences including scan emission microscopy, atomic force microscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, and thermogravimetric analysis. Circular dichroism spectra proved that the chiral information was introduced through the grafted single‐handed helical polymer chains successfully. In addition, the resulting GO/polymer composites were explored as a chiral additive to induce enantioselective crystallization of racemic organic molecules. Preferential formation of rod‐like L‐alanine crystals was induced by composites bearing right‐handed helical poly(phenyl isocyanide)s. The enantiomeric excess value of the induced crystals reached 76%, displaying the potential in future applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2092–2103  相似文献   

9.
Graphene nanosheets possess a range of extraordinary physical and electrical properties with enormous potential for applications in microelectronics, photonic devices, and nanocomposite materials. However, single graphene platelets tend to undergo agglomeration due to strong π–π and Van der Waals interactions, which significantly compromises the final material properties. One of the strategies to overcome this problem, and to increase graphene compatibility with a receiving polymer host matrix, is to modify graphene (or graphene oxide (GO)) with polymer brushes. The research to date can be grouped into approaches involving grafting‐from and grafting‐to techniques, and further into approaches relying on covalent or noncovalent attachment of polymer chains to the suitably modified graphene/GO. The present Highlight article describes research efforts to date in this area, focusing on the use of controlled/living radical polymerization techniques. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

10.
Two polyisobutylene‐grafted graphene nanocomposites were prepared by CuBr‐catalyzed atom transfer nitroxide radical coupling (ATNRC) and Cu‐catalyzed single electron transfer‐nitroxide radical coupling (SET‐NRC) chemistry under mild conditions, respectively, through the grafting‐onto strategy. Graphene oxide was first reduced to graphene by diazonium addition reaction followed by treating graphene with ethyl 2‐bromoisobutyrate for introducing Br‐containing groups onto the surface to give G‐Br. The presynthesized well‐defined functional polyisobutylene (PIB) possessing 2,2,6,6‐tetramethylpiperidine‐1‐oxyl terminal group obtained via cationic polymerization of isobutylene was then coupled with G‐Br through ATNRC or SET‐NRC at room temperature to afford polymer‐modified graphene, G‐PIB. SET‐NRC method has a faster coupling rate using cheaper reagent (Cu wire instead of CuBr) in comparison with ATNRC approach. Detailed characterizations including FT‐IR, Raman, 1H NMR, TGA, AFM, and TEM assured us of successful anchoring of PIB chains onto the surface of graphene sheets. The resulting G‐PIB nanocomposites still maintain the separated single layers in dispersion and the dispersibilities in organic solvents are significantly improved. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4505–4514  相似文献   

11.
A new approach on usage of S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate (DDAT)‐covalently functionalized graphene oxide (GO) as reversible addition fragmentation chain transfer (RAFT) agent for growing of poly(N‐vinylcarbazole) (PVK) directly from the surface of GO was described. The PVK polymer covalently grafted onto GO has Mn of 8.05 × 103, and a polydispersity of 1.43. The resulting material PVK‐GO shows a good solubility in organic solvents when compared to GO, and a significant energy bandgap of ~2.49 eV. Bistable electrical switching and nonvolatile rewritable memory effect, with a turn‐on voltage of about ?1.7 V and an ON/OFF state current ratio in excess of 103, are demonstrated in the Al/PVK‐GO/ITO structure. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

12.
This work describes a versatile method to encapsulate graphene oxide (GO) with polymers using reversible addition‐fragmentation chain transfer (RAFT) mediated emulsion polymerization. A living low molecular weight anionic macro‐RAFT statistical copolymer of sodium styrene sulfonate, acrylic acid, and butyl acrylate (BA) was synthesized using 2‐{[(butylsulfanyl)carbonothioyl] sulfanyl} propanoic acid as the chain transfer agent. GO was dispersed in water by pretreating the surface with poly(allylamine hydrochloride) (PAH), before being stabilized by the addition of the anionic macro‐RAFT copolymer. PAH was used to facilitate the adsorption of the macro‐RAFT copolymer to the GO surface via electrostatic attraction between opposite charges. The dispersed GO sheets were encapsulated with polymer by the free radical emulsion polymerization of methyl methacrylate and BA under starved fed conditions. The polymer shells encapsulating the GO sheets were formed by the chain extension of the adsorbed living macro‐RAFT copolymer. TEM, SEM, FTIR, and AFM were used to confirm the presence of the polymer layer on the surface of the GO. The thickness of the polymer coating can be adjusted by controlling the amount of monomer fed into the system. Partial polymer coatings of the GO could be achieved by varying the amount of PAH. The encapsulated GO was found to be easily dispersed in both aqueous and organic solvents over a range of polarities. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1413–1421  相似文献   

13.
Graphene‐polymer nanocomposites have significant potential in many applications such as photovoltaic devices, fuel cells, and sensors. Functionalization of graphene is an essential step in the synthesis of uniformly distributed graphene‐polymer nanocomposites, but often results in structural defects in the graphitic sp2 carbon framework. To address this issue, we synthesized graphene oxide (GO) by oxidative exfoliation of graphite and then reduced it into graphene via self‐polymerization of dopamine (DA). The simultaneous reduction of GO into graphene, and polymerization and coating of polydopamine (PDA) on the reduced graphene oxide (RGO) surface were confirmed with XRD, UV–Vis, XPS, Raman, TGA, and FTIR. The degree of reduction of GO increased with increasing DA/GO ratio from 1/4 to 4/1 and/or with increasing temperature from room temperature to 60 °C. A RAFT agent, 2‐(dodecylthiocarbonothioylthio)?2‐methylpropionic acid, was linked onto the surface of the PDA/RGO, with a higher equivalence of RAFT agent in the reaction leading to a higher concentration of RAFT sites on the surface. Graphene‐poly(methyl methacrylate), graphene‐poly(tert‐butyl acrylate), and graphene‐poly(N‐isopropylacrylamide) nanocomposites were synthesized via RAFT polymerization, showing their characteristic solubility in several different solvents. This novel synthetic route was found facile and can be readily used for the rational design of graphene‐polymer nanocomposites, promoting their applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3941–3949  相似文献   

14.
Based on a recent report [J. Polym. Sci. Part A. Polym. Chem. 2013 , 51, 47–58] whereby we demonstrated the synthesis of polystyrene nanoparticles by miniemulsion polymerization stabilized by graphene oxide (GO) nanosheets as sole surfactant, we hereby report the synthesis of hybrid polymer nanoparticles of several members of the (meth)acrylate family as well as the cross‐linker divinylbenzene via the same approach. The nature of the resultant emulsion is strongly linked to the polarity of the monomer used; monomers with a relatively small polar component (based on Hansen solubility parameters) such as lauryl methacrylate and benzyl methacrylate, in addition to styrene, generate stable emulsions that can be effectively polymerized. Particularly polar monomers (e.g., methyl acrylate and methyl methacrylate) formed kinetically stable emulsions in the presence of GO, however rapid coagulation occurred during polymerization. Electron microscopy analysis reveals the formation of polymer nanoparticles with size distribution between 200 and 1000 nm with roughened surface morphologies, indicative of GO sheets adsorbed at the interface. The results of this work demonstrate the applicability of this synthetic route for specific monomers in the preparation of novel graphene‐based polymeric materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5153–5162  相似文献   

15.
汪辉亮 《高分子科学》2017,35(10):1268-1275
Simple preparation of stimuli-responsive hydrogels with good mechanical properties and mild stimuliresponsiveness is essential for their applications as smart soft robots. Mechanically strong Janus poly(N-isopropylacrylamide)/graphene oxide (PNIPAM/GO) nanocomposite hydrogels with stimuli-responsive bending behaviors are prepared through a simple one-step method by using molds made of a Teflon plate and a glass plate. Residual oxygen in the air bubbles on the Teflon plate surface affects the polymerization and hence the cross-linking density, leading to the different swelling/deswelling rates of the two sides of the gels. Therefore, the hydrogels exhibit bending/unbending behaviors upon heating/cooling in water. The incorporation of GO nanosheets dramatically enhances the mechanical properties of Janus hydrogels. Meanwhile, the photo-responsive property of the GO nanosheets also imparts the hydrogels with remotecontrollable deformation under IR irradiation. The application of the Janus PNIPAM/GO hydrogels as thermo-responsive grippers is demonstrated.  相似文献   

16.
Simple preparation of stimuli-responsive hydrogels with good mechanical properties and mild stimuliresponsiveness is essential for their applications as smart soft robots.Mechanically strong Janus poly(Nisopropylacrylamide)/graphene oxide (PNIPAM/GO) nanocomposite hydrogels with stimuli-responsive bending behaviors are prepared through a simple one-step method by using molds made of a Teflon plate and a glass plate.Residual oxygen in the air bubbles on the Teflon plate surface affects the polymerization and hence the cross-linking density,leading to the different swelling/deswelling rates of the two sides of the gels.Therefore,the hydrogels exhibit bending/unbending behaviors upon heating/cooling in water.The incorporation of GO nanosheets dramatically enhances the mechanical properties of Janus hydrogels.Meanwhile,the photo-responsive property of the GO nanosheets also imparts the hydrogels with remotecontrollable deformation under IR irradiation.The application of the Janus PNIPAM/GO hydrogels as thermo-responsive grippers is demonstrated.  相似文献   

17.
The thermoreversible phase transition of poly(N‐isopropylacrylamide) randomly labeled with a spin label, 4‐amino‐2,2′,6,6′‐tetramethylpiperidine 1‐oxide (TEMPO), and a fluorescent dye, 4‐(pyren‐1‐yl)butyl (PNIPAM‐Py‐T), in different H2O/MeOH mixtures was studied by turbidimetry, continuous‐wave electron paramagnetic resonance spectroscopy (CW‐EPR), and fluorescence spectroscopy. The macroscopic phase diagram of PNIPAM‐Py‐T in H2O/MeOH measured by turbidimetry was identical to those of poly(N‐isopropylacrylamide) (PNIPAM) and of TEMPO‐labeled PNIPAM (PNIPAM‐T) in H2O/MeOH mixtures. However, distinct differences among the three polymers were detected in their solvent‐dependent EPR and fluorescence‐spectroscopic properties. The EPR spectra were analyzed in terms of the isotropic hyperfine coupling constants, which monitor the variation in environmental polarity of the radical labels occurring for the conformational transitions of the polymer as a function of temperature, as well as the correlation time for reorientation motion, the increase of which is indicative of the increased viscosity of the radical environment and interactions occurring between the radical and other surface groups of the precipitated polymer, if compared to the soluble polymer. The fluorescence of Py in PNIPAM‐Py‐T displayed contributions from isolated excited pyrenes (monomer emission) and from preformed pyrene ground‐state aggregates (excimer emission). The quantum efficiencies of monomer and excimer emission were monitored as a function of solvent composition. By the two experimental approaches, we demonstrate the profound influence of the PNIPAM‐attached pyrene units in increasing the hydrophobicity of the nanodomains formed upon heat‐induced precipitation of PNIPAM‐Py‐T.  相似文献   

18.
This article presents a strategy for the fabrication of hollow poly(N‐isopropylacrylamide) (PNIPAM)‐Ag nanocomposite spheres. In this approach, the thermosensitive PNIPAM hollow spheres were first synthesized via a one‐pot “self‐removing” process and then used as supporters for the coordination and in situ reduction of Ag+ ions. The results show that these hollow PNIPAM‐Ag nanocomposite spheres still have typical thermal sensitivity, and importantly, these spheres have very good and controllable catalytic activity with five stages of variation versus temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4919–4926, 2009  相似文献   

19.
A novel and universal approach towards the unique encapsulation of nanoparticles in the sandwiched graphene sheets is presented here. In the method, a low‐cost, sustainable and environmentally friendly carbon source, glucose, is firstly applied to yield the high‐quality, uniform and coupled graphene sheets in a large scale, and the pre‐fabricated hydrated nanosheets act as the sacrificial templates to generate the enveloped metallic nanoparticles. After controllable oxidation or removal of the encapsulated nanoparticles, sandwiched nanocomposite with oxidizes nanoparticles encapsulated in graphene sheets or pure phase of sandwich‐like and coupled graphene sheets would be achieved. Moreover, the synergic effect on energy storage via Li‐ion batteries is solidly verified in the Co3O4@graphene nanocomposite. More importantly, the unique structure of the nanoparticles‐encapsulated sandwiched graphene sheets will definitely result in additional applications, such as biosensors, supercapacitors and specific catalyses. These results have enriched the family of graphene‐based materials and recognized some new graphene derivatives, which will be considerably meaningful in chemistry and materials sciences.  相似文献   

20.
Surface functionalization of carbon nanotubes (CNTs) with a thermo responsive polymer was achieved via combination of mussel inspired chemistry and surface initiated single electron transfer living radical polymerization (SET‐LRP). In this procedure, CNTs were first coated with polydopamine (PDA) through self polymerization under a rather mild condition. And then PDA functionalized CNTs bearing with amino and hydroxyl groups were further reacted with bromo isobutyryl bromide. Finally, a thermo responsive polymer poly(N‐isopropylacrylamide) (PNIPAM) was introduced on the CNTs via SET‐LRP. The successful surface modification of CNT‐PDA‐PNIPAM was evidenced by a series of characterization techniques. The resulting CNT‐PDA‐PNIPAM showed significant enhancement of dispersibility in both aqueous and organic solvents. More importantly, these CNT‐polymer nanocomposites showed obvious thermo responsive behavior due to the surface coating CNTs with PNIPAM. As compared with previous methods, this method is not required oxidation of CNTs to introduce funcitonal groups for immobilization of the polymerization initiators. More importantly, this method could also be utilized for fabricating many other polymer nanocomposites because of the strong and universal adhesive of PDA to various materials. It is therefore, the novel strategy via marrying mussel inspired chemistry with SET‐LRP should be a simple, general and effective method for surface functionalization. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1872–1879  相似文献   

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