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1.
    
The core–shell Ag@C nanoparticles were prepared by hydrothermal method. The silver cores with diameters from 100 to 120 nm are each covered with a carbon shell about 60–80‐nm thick. Ag@C/poly(vinylidene fluoride) (PVDF) composites were prepared by the solution cast method. Transmission electron microscopy showed that the Ag@C core–shell nanoparticles were dispersed homogenously in the PVDF matrix with little agglomeration. The crystallization behavior and dielectric properties of the Ag@C/PVDF composites as a function of frequency and temperature were studied. The differential scanning calorimeter measurements showed that the crystallinity of the Ag@C/PVDF composites decreased with the increasing content of the Ag@C nanoparticles. The dielectric tests showed that the permittivity of the Ag@C/PVDF composites increased obviously over that of the pure PVDF with increasing content of Ag@C particles because of the enhanced interfacial polarization. The tan δ of the composites remained at a low level (～0.08 at 1000 Hz). Furthermore, the permittivity and the tan δ of the composites increased with increasing temperature. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

2.
    
A core–shell nanosilica (nano‐SiO2)/fluorinated acrylic copolymer latex, where nano‐SiO2 served as the core and a copolymer of butyl acrylate, methyl methacrylate, and 2,2,2‐trifluoroethyl methacrylate (TFEMA) served as the shell, was synthesized in this study by seed emulsion polymerization. The compatibility between the core and shell was enhanced by the introduction of vinyl trimethoxysilane on the surface of nano‐SiO2. The morphology and particle size of the nano‐SiO2/poly(methyl methacrylate–butyl acrylate–2,2,2‐trifluoroethyl methacrylate) [P(MMA–BA–TFEMA)] core–shell latex were characterized by transmission electron microscopy. The properties and surface energy of films formed by the nano‐SiO2/P(MMA–BA–TFEMA) latex were analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, and static contact angle measurement. The analyzed results indicate that the nano‐SiO2/P(MMA–BA–TFEMA) latex presented uniform spherical core–shell particles about 45 nm in diameter. Favorable characteristics in the latex film and the lowest surface energy were obtained with 30 wt % TFEMA; this was due to the optimal migration of fluorine to the surface during film formation. The mechanical properties of the films were significantly improved by 1.0–1.5 wt % modified nano‐SiO2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

3.
    
Conductive polymer particles, polyaniline (PANI)‐coated poly(methyl methacrylate–butyl acrylate–acrylic acid) [P(MMA–BA–AA)] nanoparticles, were prepared. The P(MMA–BA–AA)/PANI core–shell complex particles were synthesized with a two‐step miniemulsion polymerization method with P(MMA–BA–AA) as the core and PANI as the shell. The first step was to prepare the P(MMA–BA–AA) latex particles as the core via miniemulsion polymerization and then to prepare the P(MMA–BA–AA)/PANI core–shell particles. The aniline monomer was added to the mixture of water and core nanoparticles. The aniline monomer could be attracted near the outer surface of the core particles. The polymerization of aniline was started under the action of ammonium persulfate (APS). The final product was the desired core–shell nanoparticles. The morphology of the P(MMA–BA–AA) and P(MMA–BA–AA)/PANI particles was characterized with transmission electron microscopy. The core–shell structure of the P(MMA–BA–AA)/PANI composites was further determined by Fourier transform spectroscopy and ultraviolet–visible measurements. The conductive flakes made from the core–shell latexes were prepared, and the electrical conductivities of the flakes were studied. The highest conductivity of the P(MMA–BA–AA)/PANI pellets was 2.05 S/cm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

4.
    
Poly(urethane acrylate) (PUA) composite particles were prepared by seeded surfactant‐free emulsion polymerization. The aqueous polyurethane (PU) dispersions were used as seed particles. The diameters of the seed particles of the aqueous PU dispersions and PUA composite latexes were measured by dynamic light scattering. The microstructures of the PUA composite emulsion particles were observed by transmission electron microscopy. The influences of the amount of the hydrophilic chain extender, the types of initiators, and the PU/polyacrylate (PA) weight ratios on the diameters of the aqueous PU and composite emulsions were also studied. The results showed that the PUA composite emulsions formed a core–shell structure with PU as the shell and with PA as the core. The diameter of the PU seed particles and the particle size of the PUA composite emulsions greatly depended on the amounts of the hydrophilic chain extender used in the preparation of the PU seed; when the hydrophilic chain extender concentration was 7.4%, the average diameter of the PUA composite emulsion particles showed the minimum value. The types of initiators and PU/PA weight ratios did not have a significant influence on the diameter of the PUA composite latex particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

5.
    
Interfacially initiated microemulsion copolymerizations of n‐butyl methacrylate (BMA) and N‐vinyl pyrrolidone (NVP) by the redox initiation couple of benzoyl peroxide and ferrous sulfate were carried out with Tween 80 and n‐butanol as the surfactant and cosurfactant, respectively. Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy were recorded to analyze the chemical composition of the latex particles. Transmission electron microscopy was used to observe the particle morphology and dynamic light scattering to determine the particle size. The results demonstrated that interfacially initiated microemulsion polymerization prompted the copolymerization of the water‐soluble NVP monomer with the oil‐soluble BMA monomer to form core–shell nanoparticles. The influence of the surfactant concentration, BMA amount, and temperature on the particle size and polymerization rate was investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3751–3757, 2006  相似文献   

6.
    
Maleic anhydride functionalized acrylonitrile–butadiene–styrene copolymer (ABS‐g‐MA) was used as an impact modifier of polyamide 6 (PA6). Epoxy resin was introduced into PA6/ABS‐g‐MA blends to further improve their properties. Notched Izod impact tests showed that the impact strength of PA6/ABS‐g‐MA could be improved from 253 to 800 J/m with the addition of epoxy resin when the ABS‐g‐MA content was set at 25 wt %. Differential scanning calorimetry results showed that the addition of epoxy resin made the crystallization temperature and melting temperature shift to lower temperatures; this indicated the decrease in the PA6 crystallization ability. Dynamic mechanical analysis testing showed that the addition of epoxy resin induced the glass‐transition temperature of PA6 and the styrene‐co‐acrylonitrile copolymer phase to shift to higher temperatures due to the chemical reactions between PA6, ABS‐g‐MA, and epoxy resin. The scanning electron microscopy results indicated that the ABS‐g‐MA copolymer dispersed into the PA6 matrix uniformly and that the phase morphology of the PA6/ABS‐g‐MA blends did not change with the addition of the epoxy resin. Transmission electron microscopy showed that the epoxy resin did not change the deformation mechanisms of the PA6/ABS‐g‐MA blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

7.
    
In the electroless plating process, to omit a sensitizing process with SnCl2, we utilized amino‐functional groups on polymer particles. At first, highly monodisperse functional polymer particles could be prepared by a two‐step seeded polymerization of styrene, divinylbenzene, and glycidyl methacrylate. Then, surface epoxy‐functional groups were converted to amino‐functional groups by treating the particles with a diamine. By using these surface amino functionalities, we tried to prepare uniformly metal‐coated monodisperse polymer particles by electroless plating method. The constituents of an electroless nickel solution bath are nickel salt, a reducing agent, suitable complexing agents, and stabilizers. And the metal thickness was simply controlled by changing the loading amount of substrate polymer particles. Morphological observation of nickel‐plated polymer particles was conducted by using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The structural composition of plated nickel was also investigated. Most of all, the function and the efficiency of the amino‐functional group of polymer particles as a polymeric ligand for metal binding was elucidated. From all observations, it was evident that in the electroless metal plating process without any sensitization step, the deposition of metal clusters on substrate particles is largely dependent upon the particle surface functionality. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3801–3808, 2006  相似文献   

8.
    
Glycidyl methacrylate functionalized acrylonitrile–butadiene–styrene (ABS‐g‐GMA) particles were prepared and used to toughen polylactide (PLA). The characteristic absorption at 1728 cm?1 of the Fourier transform infrared spectra indicated that glycidyl methacrylate (GMA) was grafted onto the polybutadiene phase of acrylonitrile–butadiene–styrene (ABS). Chemical reactions analysis indicated that compatibilization and crosslinking reactions took place simultaneously between the epoxy groups of ABS‐g‐GMA and the end carboxyl or hydroxyl groups of PLA and that the increase of GMA content improved the reaction degree. Scanning electron microscopy results showed that 1 wt % GMA was sufficient to satisfy the compatibilization and that ABS‐g‐GMA particles with 1 wt % GMA dispersed in PLA uniformly. A further increase of GMA content induced the agglomeration of ABS‐g‐GMA particles because of crosslinking reactions. Dynamic mechanical analysis testing showed that the miscibility between PLA and ABS improved with the introduction of GMA onto ABS particles because of compatibilization reactions. The storage modulus decreased for the PLA blends with increasing GMA content. The decrease in the storage modulus was due to the chemical reactions in the PLA/ABS‐g‐GMA blends, which improved the viscosity and decreased the crystallization of PLA. A notched impact strength of 540 J/m was achieved for the PLA/ABS‐g‐GMA blend with 1 wt % GMA, which was 27 times than the impact strength of pure PLA, and a further increase in the GMA content in the ABS‐g‐GMA particles was not beneficial to the toughness improvement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

9.
    
To describe the morphology of the core–shell latex particle of methyl methacrylate–butadiene–styrene graft copolymer (MBS) quantitatively, we propose four parameters, that is, the diameter of the core, the shell thickness (TH), the roundness of the core, and the eccentricity (E); we calculated these parameters with geometrical parameters determined by the analysis of transmission electron microscope images. The mean values and distributions of the four parameters based on a certain amount of particles were used for quantitative characterization of MBS latex samples. With increasing monomer‐to‐polymer ratios of the graft polymerization, both the MBS TH and the numbers of homopolymer particles increased, and the core–shell morphology tended to be irregular. For the MBS latices derived from poly(styrene–butadiene) latex with a wide distribution of particle sizes, the core–shell structures of the larger particles were different from those of smaller ones to a certain extent, and both the TH and the E decreased with increasing core size. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 855–861, 2003  相似文献   

10.
    
Fe3O4/poly(styrene‐co‐maleic anhydride) core–shell composite microspheres, suitable for binding enzymes, were prepared using magnetite particles as seeds by copolymerization of styrene and maleic anhydride. The magnetite particles were encapsulated by polyethylene glycol, which improved the affinity between the magnetite particles and the monomers, thus showing that the size of the microspheres, the amount of the surface anhydrides, and the magnetite content in the composite are highly dependent on magnetite particles, comonomer ratio, and dispersion medium used in the polymerization. The composite microspheres, having 0.08–0.8 μm diameter and containing 100–800 μg magnetite/g microspheres and 0–18 mmol surface‐anhydride groups/g microsphere, were obtained. Free α‐amylase was immobilized on the microspheres containing reactive surface‐anhydride groups by covalent binding. The effects of immobilization on the properties of the immobilized α‐amylase [magnetic immobilized enzyme (MIE)] were studied. The activity of MIE and protein binding capacity reached 113,800 U and 544.3 mg/g dry microspheres, respectively. The activity recovery was 47.2%. The MIE had higher optimum temperature and pH compared with those of free α‐amylase and showed excellent thermal, storage, pH, and operational stability. Furthermore, it can be easily separated in a magnetic field and reused repeatedly. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 328–335, 2005  相似文献   

11.
    
Polyurethane (PU)/acrylate hybrids with different acrylic contents (10, 30, 50, 70, and 90 wt %) were prepared by the polymerization of acrylic monomers in the presence of preformed PU chains with polymerizable terminal vinyl groups. Films obtained by the casting of polymer dispersions before and after thermal annealing were characterized by dynamic light scattering, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), TEM electron energy‐loss spectroscopy, differential scanning calorimetry, and gel fraction determination. Small‐angle X‐ray scattering (SAXS), wide‐angle X‐ray scattering, mechanical properties testing, atomic force microscopy, water contact angle testing, Buchholz hardness testing, and roughness testing of the films were also performed. The effects of the acrylic content and thermal treatment on the structure and properties were determined. TEM showed that a core–shell morphology was formed during polymerization. When the acrylic content increased, smaller particles without core–shell morphologies were observed. TEM energy‐loss spectroscopy studies confirmed this observation. Systems with up to 50 wt % acrylic component were homogeneous, as determined by SAXS, before and after thermal annealing. An attempt to incorporate a higher amount of acrylic component led to phase‐separated materials with a different morphology and, therefore, different properties. The relationship between the acrylic content and properties did not follow linear behavior. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

12.
    
All‐atom molecular dynamics simulations were used to study the morphology of polymer/inorganic composite particles prepared by heterocoagulation. The results were also compared to those of our previous study of the preparation of TiO2/poly(acrylic acid‐co‐methyl methacrylate) and Fe3O4/polystyrene composite particles. In the simulation system, polymer or inorganic particles were simulated by surface‐charge‐modified C60 or Na atoms. Through a combination of analysis of the radial distribution functions of charged atoms and snapshots of the equilibrated structure, three kinds of particle distributions were observed under different conditions. When the polymer and inorganic particles had opposite surface charges and their sizes were very different, the composite morphology showed a core–shell structure with small particles adsorbed onto the surfaces of large particles. Furthermore, when the polymer and inorganic particles had opposite surface charges but comparable sizes, the polymer and inorganic particles aggregated domain by domain. Finally, when the polymer and inorganic particles were endowed with the same surface charge, the distribution of these two types of particles was homogeneous, regardless of their size difference. The simulation results were in agreement with the experimental results. The electrostatic interaction and the size of the particles dominated the final morphology of the composite particles when the heterocoagulation method was used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

13.
    
Free‐radical suspension polymerization was used to synthesize thermally expandable microspheres (TEMS); in this process, a poly(acrylonitrile‐co‐methacrylonitrile) shell encapsulated isooctane. Different amounts of dimethacrylate, diacrylate, or divinyl ether functional crosslinker were added to investigate the effects on the crosslinking density of the polymer and the expansion properties of the TEMS. The optimum amount of crosslinker was found to be approximately 0.05–0.1 mol %. However, a significantly better expansion could be obtained with 1,4‐butanediol dimethacrylate as a crosslinker, compared to 1,4‐butanediol divinyl ether or 1,4‐butanediol diacrylate. From monitoring the conversion of monofunctional analogues by gas chromatography, we suggest that the differences in expansion obtained with different crosslinkers, originated from the difference in the reactivity of the radicals in the system toward the vinyl functionalities of the crosslinkers. This regulated the incorporation of the crosslinker into the polymer and, thereby, the mechanical properties of the microsphere shell. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

14.
    
A novel spinning acrylic polymer containing silk protein was synthesized by copolymerization of acrylonitrile (AN) and silk fibroin peptide (SFP) modified by acryloyl chloride (AC) with vinyl groups. From results of the examination to the chemical compositions, we established that the modified SFP is more reactive than AN in the copolymerization. The intrinsic viscosity values of these copolymers showed that the copolymers have good spinnability, which were synthesized under the condition of adding a trace of metal ions into the synthesizing solvent. These copolymers exhibited good thermal property. The fiber based on the poly(acrylonitrile‐co‐silk fibroin peptide) was prepared and characterized by SEM, FTIR measurement of its shell and core flakes, and moisture absorption. The fiber exhibited a smooth surface and could be assumed to have excellent adhesive property between SFP and PAN. Furthermore, these fibers showed a core–shell structure and excellent moisture absorption. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1540–1547, 2004  相似文献   

15.
    
Thermally expandable core/shell particles with a poly(acrylonitrile‐co‐methacrylonitrile) shell and a hydrocarbon core (blowing agent) have been prepared by suspension polymerization. The objective of this study was to gain a deeper understanding of the parameters determining the expansion properties of these microspheres. It was found that the amount, the boiling point, and the structure of the blowing agent are important parameters for the expansion properties. For example, a higher maximum expansion was reached when using bulkier blowing agents and thus a lower diffusion rate through the polymer shell. Further, the amount and structure of the crosslinker were also found to be essential for the expansion properties. For this particular system, it was found that a dimethacrylate‐functional crosslinker gave significantly better expansion when compared with diacrylate‐ or divinylether‐based crosslinkers. Beside these parameters, it was also observed that the particle‐size distribution influence the expansion properties of the microspheres. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

16.
    
The controlled thermal release of aqueous solvent mixtures from polymeric gel particles was investigated. A new type of a polymeric gel consisting of a maleic anhydride/poly(ethylene glycol) condensation product as a crosslinking macromonomer and acrylamides was synthesized by solution or inverse emulsion polymerization for the investigation. Afterward a shell of crosslinked polystyrene was coated to stabilize this new kind of “microcontainer” for the application. This concept was shown as generally useful for various mixtures of organic solvents and water. The cloud point temperature of the polymer gel strongly depended on the following parameters: the type and content of organic cosolvent, the degree of polymerization and constituents of the polyester moiety, and the type and content of the comonomers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007  相似文献   

17.
    
A macroazoinitiator (MAI) containing a poly(ethylene oxide) (PEO) block was used with a methyl methacrylate monomer to prepare polymer particles in ethanol/H2O solutions. The effects of the monomer/MAI ratio (RMI) and H2O content in the solutions on the molecular weight, particle diameters, and chemical structure of the resulting polymer particles were investigated. The reaction mixtures showed three kinds of states, which were milky colloid solutions, macrogels and/or precipitations, and clear solutions. The colloid solutions were obtained in the solutions with an H2O content of about 50–90 vol % and a RMI of 20–400. In the colloid solutions, core–shell nanospheres consisting of PEO shells and poly(methyl methacrylate) (PMMA) cores were predominantly obtained. In the specific conditions close to the area of gel and/or precipitation formation, particles connected about 0.5–5 μm in length were obtained. Multiblock copolymers nanospheres tended to be obtained with lower RMIs, and PMMA‐PEO‐PMMA tri‐bloc and/or PMMA‐PEO di‐block copolymer nanospheres were obtained with higher RMIs. The solubility of the monomer and the generated polymer in solutions may have affected the polymerization development and the state of the products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

18.
    
It is understood that a major controlling factor in the development of latex particle morphology is the extent to which second stage oligomeric radicals can diffuse into the particles after entry from the aqueous phase. This leads to the expectation that any factor which decreases the diffusion rate of second stage radicals should decrease radical penetration, and thus favor the formation of core–shell type morphologies. The occurrence of crosslinking reactions during the second stage may be one such factor, since the branched and crosslinked chains diffuse much more slowly (if at all) than their linear counterparts. This paper addresses the effect of the addition of crosslinking agent (a divinyl monomer) during the second stage polymerization on particle morphology. It is shown experimentally that, contrary to what one might expect, crosslinking during the second stage has very little, if any, effect on morphology. Modeling suggests that the reason is that the probability for radicals to develop a branch before penetrating a significant distance into the particles is very low (under conditions where full penetration is possible in the absence of crosslinking agent), especially for what is considered to be typical concentrations of crosslinking agent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2043–2054, 2006  相似文献   

19.
    
In the absence of emulsifier, we prepared stable emulsifier‐free polymethylmethacrylate/polystyrene (PMMA/PSt) copolymer latex by batch method with comonomer N,N‐dimethyl, N‐butyl, N‐methacryloloxylethyl ammonium bromide (DBMEA) by using A1BN as initiator. The size distribution of the latex particles was very narrow and the copolymer particles were spherical and very uniform. Under the same recipe and polymerization conditions, PMMA/PSt and PSt/PMMA composite polymer particle latices were prepared by a semicontinuous emulsifier‐free seeded emulsion polymerization method. The sizes and size distributions of composite latex particles were determined both by quasi‐elastic light scattering and transmission electron microscopy (TEM). The effects of feeding manner and staining agents on the morphologies of the composite particles were studied. The results were as follows: the latex particles were dyed with pH 2.0 phosphotungestic acid solution and with uranyl acetate solution, respectively, revealing that the morphologies of the composite latex particles were obviously core–shell structures. The core–shell polymer structure of PMMA/PSt was also studied by 1H, 13C, 2D NMR, and distortionless enhancement by polarization transfer, or DEPT, spectroscopy. Results showed that PMMA/PSt polymers are composed of PSt homopolymer, PMMA homopolymer, and PMMA‐g‐PSt graft copolymers; results by NMR are consistent with TEM results. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1681–1687, 2005  相似文献   

20.
    
Poly(urea–formaldehyde) (PUF) microcapsules loaded with sulfur were prepared by in situ polymerization. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry and thermogravimetric (TG) analysis were used for the characterization of the obtained microcapsules. The chemical structure of the microcapsules was determined by FTIR. SEM analysis showed that the microcapsules were spherical and that the mean diameter of microcapsules was 42 ± 1 μm. Thermal analysis showed that the microcapsules were thermally stable below 247°C. The release properties of sulfur from the PUF microcapsules during the vulcanization of acrylonitrile–butadiene rubber (NBR) were studied by analysis of the vulcanization properties. The results show that at a vulcanizing temperature of 160°C, all of the sulfur entrapped in PUF was released out through the microcracks and pores of the shell, and the curing time of the microcapsule curing system compared with that of the sulfur curing system was longer. The mechanical properties of the NBR vulcanized by sulfur microcapsules were better than those of the NBR vulcanized by sulfur. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

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