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1.
Layer‐structured poly(vinyl alcohol)/graphene oxide nanocomposites in the form of films are prepared by simple solution processing. The structure and properties of these nanocomposites are studied using X‐ray diffractions, scanning electron microscopy, Fourier‐transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The results indicate that graphene oxide is dispersed on a molecular scale and aligned in the poly(vinyl alcohol) matrix, and there exists strong interfacial interactions between both components, which are responsible for the significant improvement in the thermal and mechanical properties of the nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

2.
Research on platinum catalysts with high activity and long life for hydrosilylation has attracted a great deal of interest because of the increasing price of platinum metal. In this study, we examined the effect of the molecular weight of carboxyl‐ended hyperbranched polyester/platinum complexes (HTD‐n–Pt's, where n = 1, 2, 3, or 4) on hydrosilylation activity and self‐assembled morphology. Relevant parameters tuning the morphology of self‐assemblies, such as the temperature, time, concentration, and relative humidity, were examined. All of the HTD‐n–Pt's with various molecular weights had much higher hydrosilylation activities than did the conventional homogeneous Speier's catalyst, and the HTD‐n–Pt could be self‐assembled into ordered two‐dimensional treelike structures with a fractal dimension ranging from 1.48 to 1.83; this indicated perfect fractal properties. With the increase of the HTD‐n–Pt molecular weight, the size of the self‐assembled treelike structures and the catalytic activity increased first and then decreased. The self‐assembly mechanism was speculated and analyzed by dynamic light scattering, X‐ray photoelectron spectroscopy, X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy; these suggested good agreement with the diffusion‐limited aggregation theory of particles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41416.  相似文献   

3.
Organic–inorganic nanocomposites consisting of co‐poly(vinyl chloride‐vinyl acetate‐vinyl alcohol) and silica were prepared via sol–gel process. Two types of hybrids were prepared, one in which interactions between hydroxyl group present in the copolymer chain and silanol groups of silica network were developed. In the second set, extensive chemical bonding between the phases was achieved through the reaction of hydroxyl groups on the copolymer chains with 3‐isocyanatopropyltriethoxysilane (ICTS). Hydrolysis and condensation of tetraethoxysilane and pendant ethoxy groups on the chain yielded inorganic network structure. Mechanical and thermal behaviors of the hybrid films were studied. Increase in Young's modulus, tensile strength, and toughness was observed up to 2.5 wt % silica content relative to the neat copolymer. The system in which ICTS was employed as binding agent, the tensile strength and toughness of hybrid films increased significantly as compared to the pure copolymer. Thermogravimetric analysis showed that these nanocomposite materials were stable up to 250°C. The glass transition temperature increases up to 2.5 wt % addition of silica in both the systems. Field emission scanning electron microscope results revealed uniform distribution of silica in the copolymer matrix. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

4.
The effects of pH profile and “soft template” during aniline chemical oxidative polymerization (COP) were investigated and evaluated simultaneously with diethylene triamine pentaacetic acid (DTPA) as a structural directing agent. Formation of PANI nanotubes and nanoparticles, smooth microspheres, and urchin‐like microspheres were illustrated by evaluating the pH profile during aniline COP while considering the “soft template” effects of DTPA. PANI nanosheets with two semicurled edges were found in the system producing nanotubes, which provides an evidence for the “curling mechanism” of PANI nanotube formation. With different pH profiles, chemical structures and aggregation structures of the as‐synthesized PANI micro/nanostructures are similar, whereas their conductivity, wettability, Cr (VI) adsorption, and electrochemical behaviors are distinct. The present study indicates that if properly conducted, pH profile adjustment is more effective than “soft template” to control the morphology and to optimize the performance of PANI micro/nanostructures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42403.  相似文献   

5.
A green approach is employed to prepare mechanically enhanced composites by adding noncovalently proanthocyanidin (PC)‐modified graphene (PC‐rGO) into poly(vinyl alcohol) (PVA). Ascorbic acid (AA) is used as the reducing agent, and PC is used as a dispersant to synthesize low‐defect and fully dispersed graphene. After static treatment, the PC‐rGO sheets in the composite form a horizontally arranged structure. Compared with neat PVA, the Young's modulus of the graphene‐modified composites is significantly enhanced by approximately 79.3% with incorporation of 0.9 wt% PC‐rGO. The composites incorporated with GO or AA‐rGO (without PC) have randomly distributed GO structures and apparent rGO agglomeration, resulting in a weaker mechanical property. The dispersibility, degree of defects, distribution state of graphene, and interactions with the polymer matrix are directly related to the final mechanical performance. This new approach to mechanically enhance graphene‐embedded PVA composites provides the possibility for large‐scale production of graphene‐reinforced composite materials.  相似文献   

6.
Poly(styrene‐block‐4‐vinylpyridine) (PS4VP)–CdS nanocomposites containing different concentrations of CdS were synthesized by an in situ method. Scanning electron microscopy and transmission electron microscopy results indicate that the morphologies of PS4VP–Cd(II) and PS4VP–CdS were controlled by the Cd(II) concentration and the solvent, respectively. The effects of the CdS concentration on the crystal style of CdS in PS4VP–CdS and the photoluminescence (PL) properties of the PS4VP–CdS were also examined. By a comparison of the PL spectra of PS4VP–CdS in solutions, films, and powders, the PL mechanism of PS4VP–CdS was also delivered. The PS4VP–CdS nanocomposite shows potential for application in water‐soluble fluorescence probes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

7.
Poly(L ‐lactide) (PLA)/silica (SiO2) nanocomposites containing 1, 3, 5, 7, and 10 wt % SiO2 nanoparticles were prepared by melt compounding in a Haake mixer. The phase morphology, thermomechanical properties, and optical transparency were investigated and compared to those of neat PLA. Scanning electron microscopy results show that the SiO2 nanoparticles were uniformly distributed in the PLA matrix for filler contents below 5 wt %, whereas some aggregates were detected with further increasing filler concentration. Differential scanning calorimetry analysis revealed that the addition of SiO2 nanoparticles not only remarkably accelerated the crystallization speed but also largely improved the crystallinity of PLA. An initial increase followed by a decrease with higher filler loadings for the storage modulus and glass‐transition temperature were observed according to dynamic mechanical analysis results. Hydrogen bonding interaction involving C?O of PLA with Si? OH of SiO2 was evidenced by Fourier transform infrared analysis for the first time. From the mechanical tests, we found that the tensile strength and modulus values of the nanocomposites were greatly enhanced by the incorporation of inorganic SiO2 nanoparticles, and the elongation at break and impact strength were slightly improved. The optical transparency of the nanocomposites was excellent, and it seemed independent of the SiO2 concentration; this was mainly attributed to the closed refractive indices between the PLA matrix and nanofillers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

8.
In this research, hydroxyl‐terminated polyether‐block‐polydimethylsiloxane (PESO) was synthesized as an intermediate through the hydrosilylation of Si? H‐terminated polydimethylsiloxane with allyl polyoxyethylene polyoxypropylene ether. Then, carboxylated polyether‐block‐polydimethylsiloxane (CPES) was prepared through the reaction of maleic anhydride with PESO. First, the chemical structures of the synthesized polysiloxanes were characterized with IR and 1H‐NMR spectroscopy, and then the film morphology of CPES and the supermolecule self‐assembled from CPES and N‐β‐aminoethyl‐γ‐aminopropyl polydimethylsiloxane (ASO‐1) was investigated by atomic force microscopy in detail. Experimental results indicated that the superpolysiloxane that self‐assembled from CPES and ASO‐1 showed a film morphology very different from those of CPES and ASO‐1. There were not only many small, bright dots but also some big and marvelous dots circled by dots on the film surface. The morphology of dots circled by dots was estimated to result from aggregates of CPES micelles adsorbed onto the curled ASO‐1 molecule interface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

9.
A polydimethylsiloxane‐block‐poly(methyl methacrylate) (PDMS‐b‐PMMA) diblock copolymer was synthesized by the atom transfer radical polymerization method and blended with a high‐molecular‐weight poly(vinylidene fluoride) (PVDF). In this A‐b‐B/C type of diblock copolymer/homopolymer system, semi‐crystallizable PVDF (C) and PMMA (B) block are miscible due to favorable intermolecular interactions. However, the A block (PDMS) is immiscible with PVDF and therefore generates nanostructured morphology via self‐assembly. Crystallization study reveals that both α and γ crystalline phases of PVDF are present in the blends with up to 30 wt% of PDMS‐b‐PMMA block copolymer. Adding 10 wt% of PVDF to PDMS‐b‐PMMA diblock copolymer leads to worm‐like micelle morphology of PDMS of 10 nm in diameter and tens of nanometers in length. Moreover, morphological results show that PDMS nanostructures are localized in the inter‐fibrillar region of PVDF with the addition of up to 20 wt% of the block copolymer. Increase of PVDF long period by 45% and decrease of degree of crystallization by 34% confirm the localization of PDMS in the PVDF inter‐fibrillar region. © 2018 Society of Chemical Industry  相似文献   

10.
In this study, an alternative Pd activation process was developed for electroless Ni plating on polyester fabric modified with a self‐assembled monolayer (SAM) of 3‐aminopropyltrimethoxysilane (APTMS). The presence of a highly oriented amino‐terminated SAM and the formation of Pd‐activated APTMS were demonstrated by X‐ray photoelectron spectroscopy analysis. After activation, electroless Ni plating was successfully initiated, and the Ni coating was deposited onto the surface of the polyester fibers. The resulting Ni coating was examined by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray diffraction. The electromagnetic interference (EMI) shielding effectiveness (SE) and adhesive strength of the Ni‐plated polyester fabric were evaluated. On the basis of the experimental results, the Ni coating produced with a Pd‐activated SAM was uniform and dense. As the Ni weight on the treated fabric was 32 g/m2, the EMI SE of the Ni‐plated polyester fabric modified with APTMS obtained was more than 30 dB at frequencies that ranged from 2 to 18 GHz. Compared with the conventional two‐step activation method, Ni coating on the Pd‐activated polyester fabric modified with APTMS improved the coating adherence stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

11.
Poly(vinyl chloride‐co‐vinyl acetate‐co‐maleic anhydride) (PVVM)/silica nanocomposites were prepared by the suspension radical copolymerization of the monomers in the presence of fumed silica premodified with γ‐methylacryloxypropl trimethoxy siliane. Morphological observation showed that the silica particles of nanometer scale were well dispersed in the copolymer matrix of the nanocomposites films, whereas silica particles tended to agglomerate in the composites films prepared by the solution blending of PVVM with silica. The experimental results show that the thermal stability, glass‐transition temperature, tensile strength, and Young's modulus were significantly enhanced by the incorporation of silica nanoparticles. The enhancement of properties was related to the better dispersion of silica particles in polymer matrix and the interaction between the polymer chains and the surfaces of the silica particles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

12.
A dopamine‐functionalized poly(vinyl alcohol) (PVA) elastomer with melt processability and self‐healing properties was prepared by a new chemical route of graft modification, that is, PVA carboxylation and a carbodiimide reaction. The conventional modifier for PVA sacrificed the intrinsic hydrogen‐bonding interactions and dramatically decreased the mechanical strength. The modifier dopamine, as a catechol derivative, has two hydroxyl groups, which formed hydrogen bonds with the hydroxyl groups of PVA; it also has one benzene ring, which increased the thermal stability. We found that the introduction of dopamine into the PVA molecular structure lowered the melting point, improved the thermal stability, broke the crystalline structure, and enabled thermal processing. Moreover, the modified PVA possessed good mechanical properties, could be self‐healed, and is believed to have potential applications in many fields. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45072.  相似文献   

13.
Polymer/layered‐silicate hybrids nanocomposites have attracted strong interest in today's materials research, as it is possible to achieve impressive enhancements of material properties compared to the pure polymers. In the present investigation, at first, Cloisite Na+ was modified by protonated form of natural L ‐methionine amino acid via ion‐exchange reaction to created chiral organonanoclay. Gallery spacing, interlamellar structure, and thermal stability of this novel chiral organonanoclay have been characterized using different techniques. Then it was used to fabrication of poly(vinyl alcohol) (PVA)/organonanoclay nanocomposite films (NCF)s with various compositions using solution casting method by ultrasound‐assisted method. The films were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), scanning electronic microscopy, and transmission electronic microscopy (TEM). Furthermore, thermal and optical clarity properties were investigated by thermogravimetric analysis and UV–visible transmission spectra, respectively. The TEM and XRD structure study revealed a coexistence of exfoliated and intercalated organonanoclay in the PVA matrix. The addition of organoclay into the PVA origins increases in the thermal decomposition temperatures of the NCFs. This enhancement in the thermal stability is owing to the presence of organonanoclay, which act as barriers to maximize the heat insulation and to minimize the permeability of volatile degradation products to the material. At the same time, the optical clarity of PVA/organonanoclay NCFs is not decreased in comparison with that of pure PVA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

14.
Interpenetrating polymer networks (IPNs) constructed with poly(vinyl alcohol) (PVA) and poly(diallyldimethyl ammonium chloride) (PDADMAC) using a sequential IPN method were prepared. The thermal characterization of the IPNs was investigated by differential scanning calorimetry (DSC), dielectric analysis (DEA), and thermogravimtric analysis (TGA). Decreases in the melting temperature of PVA segments in IPNs were observed with increasing PDADMAC content using DSC. DEA was employed to ascertain glass transition temperature of IPNs. The thermal decomposition of IPNs was investigated using TGA, and thermal decomposition of IPNs could be decelerated by changing PVA content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1346–1349, 2003  相似文献   

15.
The thermal and thermomechanical properties of two series of poly(ethylene oxide) networks (NPEOs) were investigated as a function of the chain length between crosslink sites (Mc) and the concentration of LiClO4 (CL) in the NPEOs. The two series of networks were produced with silica and organic crosslinking agents and, therefore, had crosslink sites of different natures: one was an inorganic silicate network (silica NPEO), and the other was an organic polar group (organic NPEO). The crosslink sites in both series of networks were commonly covalently bonded to the poly(ethylene oxide) (PEO) phase through a urethane group in the NPEOs. The glass‐transition temperatures (Tg's) of the PEO phases in the NPEOs, according to differential scanning calorimetry, increased with a decrease in Mc and were higher in the silica NPEOs than in the organic NPEOs under the same Mc conditions. The difference in Tg between the two series of networks with the same Mc values increased with decreasing Mc. These results suggested that the interaction of crosslink sites with the PEO phase was stronger in the silica NPEOs than in the organic NPEOs. The addition of LiClO4 to the NPEOs resulted in Tg of the PEO phase in the NPEOs being elevated and increased according to the increase in CL. The increase of Tg of the PEO phase according to the increase of CL in the NPEOs was retarded or saturated at high values of CL, and this indicated that the limit of solubility of the salt in the polymer was attained. The retardation or saturation of the increase of Tg was also observed in dynamic mechanical analyses. The curves of the loss factor tan δ and temperatures from the dynamic mechanical analyses for the NPEOs with high values of CL showed shoulders or double peaks indicating the existence of the second phase in the polymer networks. In the curves of tan δ for salt‐complexed NPEOs with high values of CL, silica NPEOs showed a shoulder of low intensity, but organic NPEOs showed a distinguished second peak becoming stronger with increasing CL. The results of the Tg behavior and tan δ curves suggested that the salt solubility in the NPEOs was limited and that the salt solubility of PEO in the silica NPEOs was higher than that in the organic NPEOs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 270–277, 2003  相似文献   

16.
Self‐assembled films of poly(o‐ethoxyaniline)—POEA alternated with sulfonated lignin (SL)—were successfully produced, and their kinetics of formation and growth investigated for different dopants (hydrochloric acid, methanesulfonic acid, p‐toluenesulfonic acid, and camphorsulfonic acid). These films were characterized by ultraviolet‐visible spectroscopy, atomic force microscopy, surface potential, and electrical resistance measurements. It has been observed that the bulkiest dopants led to a greater time for the polymer deposition and greater amount of material adsorbed. This can be explained by the lower mobility and lower solvation of the bulkiest dopant counterions, which led to a higher screening effect of the charges present in the POEA chains and therefore to a more compact molecular conformation. The morphology of the POEA films were also greatly affected by the type of dopant used, being rougher for the bulkiest dopants. The POEA films also exhibited different electrical responses upon ethylene exposure depending on the dopant, indicating a promising use for gas sensor applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1309–1316, 2002  相似文献   

17.
This work examines the thermal properties and phase morphology of melt‐mixed poly(trimethylene terephthalate) (PTT)/poly(hexamethylene isophthalamide) (PA 6I) blends. Two temperatures, i.e., 250 and 260°C, are used to prepare the blends, respectively. Differential scanning calorimetry results indicate the immiscible feature of the blends. It is thus concluded that the ester‐amide interchange reaction hardly occurred in the PTT/PA 6I blends. Depending on the composition and mixing temperature, the crystallization ability of PTT in the blends is either enhanced or hindered. Basically, a lower PA 6I content shifts the PTT melt crystallization to a higher temperature, whereas a higher PA 6I content causes an opposing outcome. The original complex melting behavior of neat PTT becomes more regular after the incorporation of 60 wt % or 80 wt % of PA 6I. Thermogravimetry analyses (TGA) show that the thermal stability of the blends improves as the PA 6I content increases. The two‐phased morphology of the blends is examined by scanning electron microscopy (SEM). Polarized light microscopy (PLM) results reveal that the PTT spherulites become coarser with the inclusion of PA 6I; only smaller/dispersed crystallites are observed in the blend with 20 wt % of PTT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

18.
An approach to achieve confined crystallization of ferroelectric semicrystalline poly(vinylidene fluoride) (PVDF) was investigated. A novel polydimethylsiloxane‐block‐poly(methyl methacrylate)‐block‐polystyrene (PDMS‐b‐PMMA‐b‐PS) triblock copolymer was synthesized by the atom‐transfer radical polymerization method and blended with PVDF. Miscibility, crystallization and morphology of the PVDF/PDMS‐b‐PMMA‐b‐PS blends were studied within the whole range of concentration. In this A‐b‐B‐b‐C/D type of triblock copolymer/homopolymer system, crystallizable PVDF (D) and PMMA (B) middle block are miscible because of specific intermolecular interactions while A block (PDMS) and C block (PS) are immiscible with PVDF. Nanostructured morphology is formed via self‐assembly, displaying a variety of phase structures and semicrystalline morphologies. Crystallization at 145 °C reveals that both α and β crystalline phases of PVDF are present in PVDF/PDMS‐b‐PMMA‐b‐PS blends. Incorporation of the triblock copolymer decreases the degree of crystallization and enhances the proportion of β to α phase of semicrystalline PVDF. Introduction of PDMS‐b‐PMMA‐b‐PS triblock copolymer to PVDF makes the crystalline structures compact and confines the crystal size. Moreover, small‐angle X‐ray scattering results indicate that the immiscible PDMS as a soft block and PS as a hard block are localized in PVDF crystalline structures. © 2019 Society of Chemical Industry  相似文献   

19.
In this study, we examined the effect of vanadium pentoxide (V2O5) on the mechanical, thermal, and morphological properties of poly(vinyl alcohol) (PVA)/V2O5 nanocomposites. The PVA/V2O5 nanocomposites were prepared by solution mixing, followed by film casting. The results show that the Young's moduli of the resulting nanocomposites films were higher than the pure PVA modulus with increasing V2O5 content, and it reached a maximum point at about 0.4 wt % V2O5 content at 8.55 GPa. The tensile strength and stress at break increased with increasing V2O5 content. The addition of V2O5 did not affect the melting temperature. The crystallization temperatures of PVA were significantly changed with increasing V2O5 content. The 5% weight loss degradation temperature of the nanocomposites was measured by thermogravimetric analysis. The degradation temperatures of the V2O5 nanocomposites increased with increasing filler content and were higher than the degradation temperature of pure PVA; this showed a lower thermal stability compared to those of the nanocomposites. The results show that the thermal stability increased with the incorporation of V2O5 nanoparticles. The dielectric constant of PVA had a tendency to improve when the dispersion of particles was effective. The morphology of the surfaces the nanocomposites was examined by scanning electron microscopy. We observed that the dispersion of the V2O5 nanoparticles was relatively good; only few aggregations existed after the addition of the V2O5 nanoparticles at greater than 0.4 wt %. In perspective, the addition of 0.4 wt % V2O5 nanoparticles into PVA maximized the mechanical, thermal, and electrical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

20.
Nanocomposites of ethylene‐vinyl acetate copolymer (EVAL) with Dellite organoclay were prepared in a laboratory extruder. The extent of intercalation of the nanocomposites was studied by field emission scanning electron microscopy and X‐ray diffraction. It was established that the organoclay is well dispersed and preferentially embedded in the EVAL phase. Further, the intercalation degree of the organoclay decreased with increasing organoclay content. The mechanical properties of the nanocomposites were studied as a function of clay loading and EVAL type. The nanocomposites exhibited enhanced thermal stability as seen in thermogravimetric studies. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers  相似文献   

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