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1.
Confined crystallization behaviors in polyethylene/silica nanocomposites: Synergetic effects of interfacial interactions and filler network
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Weiwei Zhao Yunlan Su Xia Gao Qingyun Qian Xin Chen Robert Wittenbrink Dujin Wang 《Journal of Polymer Science.Polymer Physics》2017,55(6):498-505
The confinement effects introduced by nanoparticles have been reported to influence the phase behaviors thus the properties of polymer nanocomposites. In this study, molecular dynamics and crystallization behaviors of polyethylene (PE) composited with three types of silica (SiO2) nanoparticles, namely unmodified SiO2, hydrophobically modified SiO2, SiO2‐APTES (3‐aminopropyltriethoxysilane) and SiO2‐PTES (n‐propyltriethoxysilane), were systematically investigated via a combination of DSC, XRD and 1H solid‐state NMR measurements. The suppressions in crystallization and chain mobilities of PE rank in the order of unmodified SiO2 < SiO2‐APTES < SiO2‐PTES due to the increasing interfacial interactions between PE and SiO2 nanoparticles. Additionally, independent of polymer–nanoparticle interactions, a silica network forms for all three kinds of nanocomposites when SiO2 content reaches 83 wt %. The mobilities of polymer chains are severely restricted by such a percolated network structure, leading to a turning point in the crystallization ability of nanocomposites and a new crystallization peak at 45 °C lower than that of pure PE. The synergetic effects of interfacial interactions and filler network on polymer crystallization have been thoroughly studied in this work, which will provide guidance on modifying and designing nanocomposites with controlled properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 498–505 相似文献
2.
Organic–inorganic hybrid nanocomposites composed of conductive polypyrrole (PPy) and surface modified silica (SiO2) were successfully prepared through an in situ chemical oxidative polymerization in supercritical carbon dioxide (scCO2). SiO2 nanoparticles were surface modified using 3‐methacryloxypropyltrimethoxysilane (MPTMS) in order to disperse well in the medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the SiO2 nanoparticles were encapsulated into the polymer. UV‐visible spectra of the diluted colloidal dispersions of PPy/SiO2 hybrid nanocomposites were similar to those of PPy system. Fourier transform infrared spectroscopy (FT‐IR) suggested the strong interaction between PPy and SiO2. Surface characterizations of nanocomposites were described by X‐ray photoelectron spectroscopy (XPS). The nanocomposites synthesized in scCO2 have been shown to possess higher electrical conductivity and thermal stability. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
3.
L. Reijnders 《Polymer Degradation and Stability》2009,94(5):873-876
There is a growing interest in the development of nanocomposites consisting of organic polymers and TiO2 or amorphous SiO2 nanoparticles. These nanoparticles may be released from nanocomposites. There is evidence that amorphous SiO2 and TiO2 nanoparticles can be hazardous. Thus, in the design of nanocomposites with such nanoparticles, hazard reduction extending to the full nanocomposite life cycle would seem a matter to consider. Options for hazard reduction include: changes of nanoparticle surface, structure or composition, better fixation of nanoparticles in nanocomposites, including persistent suppression of oxidative damage to polymers by nanoparticles, and design changes leading to the release of relatively large particles. 相似文献
4.
应用SiO2纳米粒子、CdTe量子点和Au纳米粒子,采用逐层吸附法制备SiO2@CdTe@Au纳米复合材料。同时对样品进行了测试和表征,从多个方面证明纳米复合材料成功制备。利用Z扫描技术测量了SiO2@CdTe和SiO2@CdTe@Au纳米复合材料在纳秒激光脉冲作用下的非线性吸收光学特性。实验结果表明:SiO2@CdTe和SiO2@CdTe@Au纳米复合材料均表现出饱和吸收特性。SiO2@CdTe@Au较SiO2@CdTe纳米复合材料具有更强的非线性光学特性,并对其机理进行了分析。 相似文献
5.
Silicone-acrylic resin (SAR) was prepared from acrylic monomers and silicone prepolymer by the free radical solution polymerization, and then mixed TiO2 and SiO2 nanoparticles modified by KH570 were added to prepare nanocomposite coating. Thermogravimetric analysis and contact angle measurements showed that the acrylic resin modified by silicone prepolymer exhibited an improved thermostability and a better hydrophobicity compared with the unmodified sample. The adding of nanoparticles further increased the hydrophobicity. The contact angle of modified silicone-acrylic resin with mixed TiO2 and SiO2 nanoparticles of 3 wt% is the highest, 108.4°. The UV resistance and weather resistance of the modified silicone-acrylic resin are significantly improved. It was also found through electrochemical impedance spectroscopy that the corrosion resistance was significantly improved by the addition of mixed TiO2 and SiO2 nanoparticles. Modified silicone-acrylic resin with mixed TiO2 and SiO2 nanoparticles of 3 wt% and 5 wt% coating system maintains an excellent anticorrosion performance (coating resistance Rc of more than 109 Ω cm2) even at 3.5% NaCl electrolyte medium till to 1800 h. 相似文献
6.
《Arabian Journal of Chemistry》2019,12(7):1186-1196
Silica (SiO2) nanoparticles and silica/calcium carbonate (SiO2/CaCO3) core–shell nanocomposites were prepared by sol–gel technique as fillers for papermaking application. Semi-burned rice straw ash (SBRSA), as waste material, was used to prepare the targeted fillers. Preparation of SiO2 nanoparticles and SiO2/CaCO3 nanocomposites was carried out using Na2SiO3 solution that was prepared from SBRSA and CaCO3 nanoparticles of 30–70 nm. The targeted SiO2/CaCO3 nanocomposites were prepared with different molar ratio of SiO2:CaCO3 1:15, 1:10 and 1:5. The percentage of silica increased from 62.5% to 82.9% by thermal treatment of SBRSA at 800 °C for 2 h. The prepared SiO2 nanoparticles and SiO2/CaCO3 nanocomposites were characterized by using XRD, XRF, TEM, FT-IR and Zeta potential. The results indicate that a pure semi-crystalline SiO2 nanoparticle and semi-crystalline shell of SiO2 coated CaCO3 core particles were produced. The work extended also to investigate the effect of the prepared fillers on physical, mechanical and optical properties of paper.Application of the prepared SiO2 nanoparticles and SiO2/CaCO3 nanocomposites improved the optical properties of paper (brightness, whiteness and opacity) but it slightly reduced the mechanical properties when compared to commercial precipitated CaCO3 (PCC) filler.The results showed that the retention of SiO2 nano-particles was highly increased. The retention of the prepared nanocomposites increased along with increasing of SiO2:CaCO3 molar ratio. 相似文献
7.
Qi Li Wenqian Wang Gaowei Hu Xianlan Cui Dejun Sun Zheng Jin Kai Zhao 《Molecules (Basel, Switzerland)》2021,26(9)
Chitosan is a non-toxic biological material, but chitosan is insoluble in water, which hinders the development and utilization of chitosan. Chitosan derivatives N-2-Hydroxypropyl trimethyl ammonium chloride (N-2-HACC) and carboxymethyl chitosan (CMCS) with good water solubility were synthesized by our laboratory. In this study, we synthesized mesoporous SiO2 nanoparticles by the emulsion, and then the mesoporous SiO2 nanoparticles were modified with γ-aminopropyltriethoxysilane to synthesize aminated mesoporous SiO2 nanoparticles; CMCS and N-2-HACC was used to cross-link the aminated mesoporous SiO2 nanoparticles to construct SiO2@CMCS-N-2-HACC nanoparticles. Because the aminated mesoporous SiO2 nanoparticles with positively charged can react with the mucous membranes, the virus enters the body mainly through mucous membranes, so Newcastle disease virus (NDV) was selected as the model drug to evaluate the performance of the SiO2@CMCS-N-2-HACC nanoparticles. We prepared the SiO2@CMCS-N-2-HACC nanoparticles loaded with inactivated NDV (NDV/SiO2@CMCS-N-2-HACC). The SiO2@CMCS-N-2-HACC nanoparticles as delivery carrier had high loading capacity, low cytotoxicity, good acid resistance and bile resistance and enteric solubility, and the structure of NDV protein encapsulated in the nano vaccine was not destroyed. In addition, the SiO2@CMCS-N-2-HACC nanoparticles could sustain slowly released NDV. Therefore, the SiO2@CMCS-N-2-HACC nanoparticles have the potential to be served as delivery vehicle for vaccine and/or drug. 相似文献
8.
G. H. Du Z. L. Liu X. Xia Q. Chu S. M. Zhang 《Journal of Sol-Gel Science and Technology》2006,39(3):285-291
A sol-gel procedure was used to cover Fe3O4 nanoparticles with SiO2 shell, forming a core/shell structure. The core/shell nanocomposites were synthesized by a two-step process. First, Fe3O4 nanoparticles were obtained through co-precipitation and dispersed in aqueous solution through electrostatic interactions
in the presence of tetramethylammonium hydroxide (TMAOH). In the second step, Fe3O4 was capped with SiO2 generated from the hydrolyzation of tetraethyl orthosilicate (TEOS). The structure and properties of the formed Fe3O4/SiO2 nanocomposites were characterized and the results indicate that the Fe3O4/SiO2 nanocomposites are superparamagnetic and are about 30 nm in size. Bioconjugation to IgG was also studied. Finally, the mechanism
of depositing SiO2 on magnetic nanoparticles was discussed. 相似文献
9.
Maryam Masjedi-Arani Davood Ghanbari Masoud Salavati-Niasari Samira Bagheri 《Journal of Cluster Science》2016,27(1):39-53
In this work spherical SiO2 nanoparticles were synthesized by sonochemical method using a new Schiff-base as a capping agent. The silica nanoparticles were obtained by hydrolysis of tetraethyl orthosilicate in aqueous alcohol solution. The effect of different parameters such as molar concentration of Schiff-base ligands and ultrasonic irradiation on the morphology and size of the products was examined. The results demonstrated that applying the appropriate amount of Schiff-base could be effective in control of particle size. The influence of SiO2 nanostructures on the flame retardancy of the poly styrene, poly vinyl alcohol, cellulose acetate and ethyl cellulose was studied. In-situ and ex situ nanocomposites were investigated and results confirm that flame retardancy of in situ nanocomposites were better than ex situ samples. HO···Si–O–Si···OH barrier prevents reaching of flame, heat and oxygen to the polymeric nanocomposites. 相似文献
10.
This study presented an effective method to modify the surface chemical reactivity of a SiO2/Fe3O4 support. The unmodified SiO2/Fe3O4 support was prepared by the hydrolysis and condensation of tetraethoxysilane on the surface of hydrophilic Fe3O4 nanoparticles. These were then modified by a heat treatment in an ethanol/water solution under reflux. The resulting samples were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission/scanning electron microscopy. The immobilization of a TiO2 nanocatalyst on both unmodified and modified supports was performed to investigate the effects of the modification of the magnetic silica support on the loading of a TiO2 nanocatalyst and the photocatalytic activity. The loading of TiO2 and the photocatalytic activity were both improved. 相似文献
11.
A series of nanocomposites consisted of poly(butylene succinate) (PBSu) and fumed silica nanoparticles (SiO2) were prepared using the in situ polymerization technique. The amount of SiO2 used directly affected the final molecular weight of the prepared polyesters. At a low SiO2 content (0.5 wt.%) the molecular weight obtained was higher compared to neat PBSu, however at higher concentrations this was gradually reduced. The melting point of the matrix remained unaffected by the addition of the nanoparticles, in contrast to the crystallinity, which was dramatically reduced at higher SiO2 contents. This was mainly due to the extended branching and cross-linking reactions that took place between the carboxylic end groups of PBSu and the surface silanols of the nanoparticles. Thermal degradation of the PBSu/SiO2 nanocomposites was studied by determining theirs mass loss during heating. From the variations of the activation energies, calculated from the thermogravimetric curves, it was clear that nanocomposites containing 1 wt.% SiO2 content had a higher activation energy compared to pure PBSu, indicating that the addition of the nanoparticles could slightly increase the thermal stability of the matrix. However, in PBSu/SiO2 nanocomposite containing 5 wt.% SiO2 the activation energy was smaller. This phenomenon should be attributed to the existence of extended branched and cross-linked macromolecules, which reduce the thermal stability of PBSu, rather than to the addition of fumed silica nanoparticles. 相似文献
12.
K. Chrissafis E. Pavlidou K. M. Paraskevopoulos T. Beslikas N. Nianias D. Bikiaris 《Journal of Thermal Analysis and Calorimetry》2011,105(1):313-323
Nanocomposites of poly(l-lactic acid) (PLLA) containing 2.5 wt% of fumed silica nanoparticles (SiO2) and organically modified montmorillonite (OMMT) were prepared by solved evaporation method. From SEM micrographs it was
observed that both nanoparticles were well dispersed into PLLA matrix. All nanocomposites exhibited higher mechanical properties
compared to neat PLLA, except elongation at break, indicating that nanoparticles can act as efficient reinforcing agents.
Nanoparticles affect, also, the thermal properties of PLLA and especially the crystallization rate, which in all nanocomposites
is faster than that of neat PLLA. From the thermogravimetric curves it can be seen that neat PLLA nanocomposites present a
relatively better thermostability than PLLA, and this was also verified from the calculation of activation energy (E). From the variation of E with increasing degree of conversion it was found that PLLA/nanocomposites decomposition takes place with a complex reaction
mechanism, with the participation of two different mechanisms. The combination of models, nth order and nth order with autocatalysis (Fn–Cn), for PLLA and PLLA/OMMT as well as the combination of Fn–Fn for PLLA/SiO2 give the better results. For the PLLA/OMMT the values of the E for both mechanisms are higher than neat PLLA. For the PLLA/SiO2 nanocomposite the value of the E is higher than the corresponding value for PLLA, for the first area of mass loss, while the E of the second mechanism has a lower value. 相似文献
13.
Unconventional Assembly of Bimetallic Au–Ni Janus Nanoparticles on Chemically Modified Silica Spheres
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Dr. Lei Jia Dr. Xiaowei Pei Prof. Feng Zhou Prof. Weimin Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):2065-2070
This paper reports that Janus Au?Ni nanoparticles (JANNPs) can self‐assemble onto silica spheres in a novel way, which is different from that of single‐component isotropic nanoparticles. JANNPs modified with octadecylamine (ODA) assemble onto catechol‐modified silica spheres (SiO2?OH) to form a very special core–loop complex structure and finally the core–loop assemblies link each other to form large assemblies through capillary force and the hydrophobic interaction of the alkyl chains of ODA. The nanocomposites disassemble in the presence of vanillin and oleic acid because of the breakage of the catechol–metal link. Vanillin‐induced disassembly enables the JANNPs to reassemble into a core–loop structure upon ODA addition. The assembly of SiO2?OH and isotropic Ni or Fe3O4 particles generates traditional core–satellite structures. This unconventional self‐assembly can be attributed to the synergistic effect of Janus specificity and capillary force, which is also confirmed by the assembly of thiol‐terminated silica spheres (SH?SiO2) with anisotropic JANNPs, isotropic Au, and Ni nanoparticles. These results can guide the development of novel composite materials using Janus nanoparticles as the primary building blocks. 相似文献
14.
《Mendeleev Communications》2023,33(2):160-163
New nanocomposites based on Fe3O4 magnetic nanoparticles coated with SiO2 or SiO2/aminopropylsilane (APS), including those using N-(phosphonomethyl)iminodiacetic acid (PMIDA), were obtained, and the immobilization of the antitumor agent doxorubicin (Dox) on nanocomposites was examined. It has been shown that the binding of Dox to the negatively charged surface of SiO2 particles occurs more efficiently than that to the APS-modified surface with positively charged amino groups; the presence of PMIDA molecules on the surface significantly increased the loading content. Based on DFT calculations, a mechanism for Dox binding to the surface of the synthesized nanocomposites was proposed. 相似文献
15.
以纳米SiO2水溶胶为原料,3?氨丙基三乙氧基硅烷(APTES)和3?氯丙基三乙氧基硅烷(CPTES)为改性剂,在水基环境下分别对SiO2纳米粒子进行改性,得到了具有亲水特性的APTES改性SiO2粒子和具有亲油特性的CPTES改性SiO2粒子水溶胶。2种粒子按不同比例混合,利用接枝在SiO2粒子表面氨基和氯丙基的取代反应,使得2种具有亲水/亲油特性的改性SiO2纳米粒子偶联,制备了粒径为40~50 nm的哑铃型SiO2纳米粒子。并通过透射电镜(TEM)、傅里叶变换红外光谱(FT?IR)、X射线光电子能谱(XPS)以及动态光散射(DLS)等方法对其进行了系统表征。结果表明,2种粒子成功偶联形成了具有哑铃型结构的水相SiO2纳米粒子,该粒子两面具有不同的亲水性,粒径近似等于APTES改性SiO2粒子和CPTES改性SiO2粒子的粒径之和。 相似文献
16.
PMMA based nanocomposites filled with calcium carbonate nanoparticles (CaCO3) have been prepared by in situ polymerization approach. In order to improve inorganic nanofillers/polymer compatibility, PBA chains have been grafted onto CaCO3 nanoparticle surface. Morphological analysis performed on nanocomposite fractured surfaces has revealed that the CaCO3 modification induces homogeneous and fine dispersion of nanoparticles into PMMA as well as strong interfacial adhesion between the two phases. Mechanical tests have shown that both unmodified and modified CaCO3 are responsible for an increase of the Young's Modulus, whereas only PBA-grafted nanoparticles allow to keep unchanged impact strength, strongly deteriorated by adding unmodified CaCO3. Finally, the presence of CaCO3 nanoparticles significantly improves the abrasion resistance of PMMA also modifying its wear mechanism. 相似文献
17.
In this paper silica nanoparticles with covalently grafted polymer chains were incorporated into bisphenol A dicyanate ester (BADCy) to prepare composites which resulted in improvements in the mechanical and thermal properties. Fourier‐transform infrared (FT‐IR) spectroscopy transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) were employed to examine the surface functionalization of silica nanoparticles. The effects of functionalized SiO2 (F‐SiO2) on the curing reactivity mechanical and thermal properties of BADCy resin were investigated systematically. The curing reaction of the system was facilitated with the addition of F‐SiO2. Meanwhile compared with the neat resin the incorporation of appropriate content of modified F‐SiO2 can enhance the mechanical properties including impact flexural strengths and fracture toughness KIC of BADCy resin. In addition the thermal stability of BADCy/F‐SiO2 nanocomposites is also superior to that of pure BADCy resin. 相似文献
18.
Xuegang Lu Gongying Liang Qianjin Sun Caihua Yang 《Journal of solid state chemistry》2010,183(7):1555-1560
Cobalt-SiO2 nanocomposites were successfully synthesized by chemical precipitation combined H2 reduction method. The influence of SiO2 matrix on the crystal structure and high frequency magnetic properties of cobalt nanoparticles was investigated. Amorphous SiO2 layer, which is adhered to Co particle surface through Si-O-Co bonds, inhibits the growth of the nanoparticles and stabilizes the face-centered-cubic (FCC) structured Co. The FCC-cobalt/SiO2 nanocomposites exhibit soft magnetic behavior with saturation magnetization (Ms) about 125 emu/g and coercivity (Hc) smaller than 100 Oe. The permeability spectra of Co/SiO2 nanocomposites depend on the SiO2 contents. When the SiO2 content is greater than 8 wt%, the permeability spectra demonstrate notable high frequency characteristic, in which the real part μ′ of the permeability is almost independent of frequency and the imaginary part μ″ remains extremely low in high frequency range. 相似文献
19.
A. A. Askadskii E. S. Afanas’ev M. D. Petunova A. I. Barabanova L. M. Goleneva V. I. Kondrashchenko O. E. Philippova 《Polymer Science Series A》2014,56(3):318-329
The effect of nanoparticles on glass-transition temperature T g and the elastic modulus of a cycloaliphatic epoxy resin cured with methylhexahydrophthalic anhydride is theoretically analyzed. The analysis was performed with allowance for the following factors: the chemical structure of the polymer, the chemical structures of the nanoparticles and their surfaces if they are modified, the concentrations and shapes of nanoparticles (spherical, plate, cylindrical), the concentration of functional groups on the surfaces of nanoparticles, the energy of intermolecular interaction between a polymer and a nanoparticle, and the possibility of chemical interaction between a polymer and the surfaces of nanoparticles. The most pronounced effect on T g is exerted by cylindical nanotubes, whose surfaces are modified with OH groups, which give rise to hydrogen bonding. The least effect is exerted by spherical nanoparticles. After the introduction of SiO2 nanoparticles, the elastic moduli of nanocomposites increase by a factor of 1.15 at an amount of nanoparticles up to 20%. 相似文献
20.
Surface of TiO2 nanoparticles was modified with the in situ chemical oxidative polymerization of aniline. Polyaniline modified TiO2 nanoparticles (PANI-TiO2 ) were characterized with the FT-IR, XRD, SEM and TEM techniques. Results confirmed that PANI was grafted successfully on the surface of TiO2 nanoparticles, therefore agglomeration of nanoparticles decreased dramatically. Polyvinyl chloride nanocomposites filled with 1 wt% 5 wt% of PANI-TiO2 and TiO2 nanoparticles were prepared via the solution blending method. PVC nanocomposites were analyzed with FT-IR, XRD, SEM, TG/DTA, DSC and tensile test techniques. Effect of PANI as surface modifier of nanoparticles was discussed according to the final properties of PVC nanocomposites. Results demonstrated that deposition of PANI on the surface of TiO2 nanoparticles improved the interfacial adhesion between the constituents of nanocomposites, which resulted in better dispersion of nanoparticles in the PVC matrix. Also PVC/PANI-TiO2 nanocomposites showed higher thermal resistance, tensile strength and Young’s modulus compared to those of unfilled PVC and PVC/TiO2 nanocomposites. 相似文献