溶胶-凝胶法聚丙烯酸丁酯/二氧化硅杂化材料弹性体的制备与表征

用丙烯酸丁酯与少量功能单体共聚,合成了分子链侧基带羟基的聚丙烯酸丁酯(PBA)乳液,然后与硅溶胶混合,用溶胶-凝胶法制备了PBA/SiO2杂化材料弹性体;研究了SiO2含量对杂化材料弹性体力学性能及透光率的影响,并用扫描电子显微镜、傅里叶变换红外光谱、差示扫描量热分析和动态力学性能分析对杂化材料弹性体的结构进行了表征。结果表明,PBA/SiO2杂化材料热压后成为一种力学性能优良的具有一定透光率的弹性体。随着SiO2含量的增加,杂化材料弹性体的力学性能提高,透光率和SiO2粒子的粒径增加,PBA基体的玻璃化转变温度和损耗因子下降;PBA共聚物分子链侧基所带羟基与SiO2粒子表面的硅醇基发生了缩合脱水反应,形成了Si—O—C共价键,使PBA基体与SiO2粒子构成的界面结合紧密,从而赋予杂化材料弹性体以优良的性能。     

Polymer/silica nanohybrids by means of tetraethoxysilane sol–gel condensation onto waterborne polyurethane particles

Stable waterborne polyurethane/silica hybrid dispersions were obtained by sol–gel reaction of tetraethoxysilane added to previously synthesized waterborne polyurethane nanodispersions. Two series of polyurethane/silica nanostructures with different silica contents were synthesized using pure polyurethane particles and polyurethane particles previously functionalized with (3-aminopropyl)triethoxysilane (APTES) as colloidal templates. The optimum experimental conditions for tetraethoxysilane sol–gel reaction (T = 75 °C and semi batch polymerization conditions) leading to the formation of silica/polyurethane aqueous nanodispersions were established. The presence of silica was confirmed using TGA, FTIR, ²⁹Si NMR and TEM. TEM images showed an excellent final dispersion of the silica nanoparticles in the polymer matrix when silane functionalized polyurethane nanoparticles were used.     

The effect of silica nanoparticles and carbon nanotubes on the toughness of a thermosetting epoxy polymer

Silica nanoparticles and multiwalled carbon nanotubes (MWCNTs) have been incorporated into an anhydride‐cured epoxy resin to form “hybrid” nanocomposites. A good dispersion of the silica nanoparticles was found to occur, even at relatively high concentrations of the nanoparticles. However, in contrast, the MWCNTs were not so well dispersed but relatively agglomerated. The glass transition temperature of the epoxy polymer was 145°C and was not significantly affected by the addition of the silica nanoparticles or the MWCNTs. The Young's modulus was increased by the addition of the silica nanoparticles, but the addition of up to 0.18 wt % MWCNTs had no further significant effect. The addition of both MWCNTs and silica nanoparticles led to a significant improvement in the fracture toughness of these polymeric nanocomposites. For example, the fracture toughness was increased from 0.69 MPam^1/2 for the unmodified epoxy polymer to 1.03 MPam^1/2 for the hybrid nanocomposite containing both 0.18 wt % MWCNTs and 6.0 wt % silica nanoparticles; the fracture energy was also increased from 133 to 204 J/m². The mechanisms responsible for the enhancements in the measured toughness were identified by observing the fracture surfaces using field‐emission gun scanning electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermally activated sintering–coarsening–coalescence-polymerization of amorphous silica nanoparticles

An onset sintering–coarsening–coalescence-polymerization (SCCP) event of amorphous SiO₂ nanoparticles (ca. 40–100 nm in size) by isothermal firing in the 1150–1300 °C range in air was characterized by an N₂ adsorption–desorption hysteresis isotherm coupled with X-ray diffraction and vibrational spectroscopy. The apparent activation energy of such a rapid SCCP process was estimated as 177±32 kJ/mol, based on 30% reduction of a specific surface area with an accompanied change of medium range orders, i.e. forming Si₂O₅ while retaining the Si–2ndO yet losing the Si–2ndSi without appreciable crystallization. The minimum temperature of the SCCP process, as of concern to industrial silica applications and sedimentary/metamorphosed sandstone formation, is 1120 °C based on the extrapolation of steady specific surface area reduction rates to null.     

Characterization and properties of activated nanosilica/polypropylene composites with coupling agents

In this work, nanosilica/polypropylene composites containing 1 wt% of silica nanoparticles were prepared by melt mixing in a Thermo Haake internal mixer. Prior compounding, nanosilica was subjected to surface activation using sodium hydroxide (NaOH) solution. The effectiveness of the activation process was evaluated by measuring the amount of hydroxyl groups ( OH) on the surface of nanosilica via titration method and supported by FTIR analysis. Two coupling agents namely 3‐aminopropyl triethoxysilane (APTES) and neopentyl (diallyl)oxy, tri(dioctyl) phosphate titanate (Lica 12) were used for surface treatment after activation process. The mechanical properties of polypropylene matrix reinforced with silica nanoparticles were determined by tensile and impact test. Hydroxyl groups on the nanosilica surface played an important role in enhancing the treatment with silane coupling agents. To increase the amount of hydroxyl groups on the nanosilica surface, the optimum concentration of NaOH is 1 mol%. Tensile strength, tensile modulus, and impact strength of nanosilica/PP composites improved with activation process. As the coupling agent is concerned, APTES coupling agent is more pronounced in enhancing the mechanical properties of the composites when compared with Lica 12 coupling agent. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Fabrication of chemically bonded polyacrylate/silica hybrid films with high silicon contents by the sol–gel method

Polyacrylate/silica hybrid latexes (PAES) with high silicon contents (up to 21%) were prepared by directly mixing colloidal silica with polyacrylate emulsion (PAE) modified by a silane coupling agent. Sol–gel-derived organic/inorganic thin films were obtained by addition of hydrophilic co-solvents to PAES and subsequent drying at room temperature. The effects of co-solvents and γ-methacryloxypropyltrimethoxysilane (KH570) content on the properties of PAES films were investigated. Dynamic light scattering (DLS) data indicated that the average diameter of PAES (96 nm) was slightly larger than that of PAE (89 nm). TEM photo revealed that colloidal silica particles were dispersed uniformly around polyacrylate particles and that some of the colloidal silica particles were adsorbed on the surface of PAE particles. The data of crosslinking degree and FT-IR spectra confirmed that the chemical structure of the PAES changed to form Si–O–Si-polymer crosslinking networks during the film formation. AFM photos, contact angle for water, and XPS analysis showed that the polyacrylate/inorganic hybrid films with high silicon contents were formed by the co-solvent-mediated, sol–gel method and that the Si-based polymers were uniformly distributed on the surface of the dried films. TGA data demonstrated that the PAES films display much better thermal stability than the PAE counterpart.     

Poly(ionic liquid) nanoparticles as novel colloidal template for silica nanocasting

Spherical poly(ionic liquid) (PIL) nanoparticles of different size (25–70 nm) were synthesized and applied as a novel colloidal soft template for the preparation of meso- and macroporous inorganics, here exemplified with silica and its metal nanoparticle doping via nanocasting. Pore size and pore architecture can be adjusted by appropriate choice of the template and the reaction conditions. Unexpectedly, it was found that the in situ generated methanol plays a very important role during the casting process. It enlarged the overall surface area by introducing a significant fraction of micropores and small mesopores. The largest specific surface area was obtained at an optimized ratio of tetramethyl orthosilicate (TMOS) to PIL nanoparticle. In addition, PIL nanoparticles pre-functionalized with Pt metal nanoparticles were used in the same manner as hybrid templates for nanocasting. The pyrolysis conditions were optimized to synthesize mesoporous silica functionalized with uniformly distributed metal nanoparticles of very small size in a one-pot process.     

荧光胺定量检测纳米SiO2表面氨基的含量

首先用3-氨丙基三乙氧基硅烷偶联剂(APTES)在一定条件下接枝于纳米二氧化硅表面,并采用傅里叶变换红外光谱仪(FI-IR)进行测试表征,建立了一种用荧光胺定量检测功能化纳米SiO2表面氨基的方法,并通过优化实验建立该检测方法的测试标准.最佳检测条件为:室温下,激发波长380 nm、发射波长480 nm,荧光胺的丙酮溶液与磷酸盐缓冲液体积比1:5,磷酸盐缓冲液pH值为10.0,反应时间为10 min等条件下,荧光信号最稳定.采用该最佳条件下制定的标准曲线对功能化纳米SiO2微球进行检测,结果符合预期,该方法检测灵敏度高、操作简单.     

Synthesis and characterization of end-functional polymers on silica nanoparticles via a combination of atom transfer radical polymerization and click chemistry

This article describes a divergent strategy to prepare grafted polymer chains with functional end groups for surface modification of nanoparticles with other functional groups. This preparation is achieved through a combination of surface-initiated atom transfer radical polymerization (ATRP) and click chemistry. First, the surface of the silica nanoparticles was modified with polystyrene (PSt) brushes via the “grafting from” approach. The terminal bromides of PSt-grafted silica nanoparticles were then substituted with azido groups. These azido-terminated PSt brushes on the nanoparticle surface were reacted with various alkyne-terminated functional end groups via click reactions. In all cases, FTIR and ¹H NMR spectra indicated quantitative transformation of the chain ends of polystyrene brushes on silica nanoparticles into the desired functional group.     

The situ preparation of silica nanoparticles on the surface of functionalized graphene nanoplatelets

A method for situ preparing a hybrid material consisting of silica nanoparticles (SiO₂) attached onto the surface of functionalized graphene nanoplatelets (f-GNPs) is proposed. Firstly, polyacrylic acid (PAA) was grafted to the surface of f-GNPs to increase reacting sites, and then 3-aminopropyltriethoxysilane (APTES) KH550 reacted with abovementioned product PAA-GNPs to obtain siloxane-GNPs, thus providing reaction sites for the growth of SiO₂ on the surface of GNPs. Finally, the SiO₂/graphene nanoplatelets (SiO₂/GNPs) hybrid material is obtained through introducing siloxane-GNPs into a solution of tetraethyl orthosilicate, ammonia and ethanol for hours'' reaction. The results from Fourier transform infrared spectroscopy (FTIR) showed that SiO₂ particles have situ grown on the surface of GNPs through chemical bonds as Si-O-Si. And the nanostructure of hybrid materials was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All the images indicated that SiO₂ particles with similar sizes were grafted on the surface of graphene nanoplatelets successfully. And TEM images also showed the whole growth process of SiO₂ particles on the surface of graphene as time grows. Moreover, TGA traces suggested the SiO₂/GNPs hybrid material had stable thermal stability. And at 900°C, the residual weight fraction of polymer on siloxane-GNPs was about 94.2% and that of SiO₂ particles on hybrid materials was about 75.0%. However, the result of Raman spectroscopy showed that carbon atoms of graphene nanoplatelets became much more disordered, due to the destroyed carbon domains during the process of chemical drafting. Through orthogonal experiments, hybrid materials with various sizes of SiO₂ particles were prepared, thus achieving the particle sizes controllable. And the factors’ level of significance is as follows: the quantity of ammonia > the quantity of tetraethyl orthosilicate (TEOS) > the reaction time.     

Hybrid Metal (Gold)-Inorganic (Silica) Nanoparticles: Synthesis,Characterization, and Spin-Labeling

Water-soluble gold nanoparticles, capped with captopril, have been synthesized and characterized. Their average size is 2.3 nm, with a spherical shape. These gold nanoparticles can be easily labeled with stable free radicals (4-amino-tempo) by a coupling reaction performed in the presence of 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ). Both synthesized and spin-labeled gold nanoparticles can be incorporated into much bigger (100 nm) silica nanoparticles using the Stober method, thus forming hybrid metal (gold)-inorganic (silica) nanoparticles. These hybrid silica nanoparticles (containing or not spin-labeled gold nanoparticles) can be easily spin-labeled with another stable free radical (4-isocyanato-tempo), leading to the formation of a double spin-labeled material. In this way, some stable free radicals are attached on the gold surface while others are attached on the silica surface. Three types of EPR spectra were recorded and discussed for the hybrid gold-silica nanoparticles: (1) where the spin labels are attached to the embedded gold nanoparticles, (2) where the spin labels are attached to the silica nanoparticles, and (3) in the case of the double spin labeled material where both gold and silica nanoparticles are spin-labeled. Influence of different solvents on the EPR spectra is also discussed.     

Immobilization of serum albumin on the synthesized three layers core–shell structures of super-paramagnetic iron oxide nanoparticles

In this study, the synthesis of four layer structures coated on magnetite nanoparticles such that Fe₃O₄/SiO₂/APTES/PEG/BSA was investigated. Magnetite nanoparticles were synthesized by co-precipitating Fe²⁺ and Fe³⁺ in an ammonia solution with the average size of 25 nm. To fabricate Fe₃O₄/SiO₂ core–shells, the magnetite nanoparticles coated by silica with Stöber method. The fabricated nanoparticles were treated by 3-aminopropyl-triethoxysilane to achieve Fe₃O₄/SiO₂/APTES nanostructures. Moreover, the nanoparticles were also attached to reactive polyethylene glycol chains. Eventually, the nanoparticles activated with bovine serum albumin for bio-application. X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, UV–vis spectroscopy and vibrating sample magnetometer were used to support the characterization.     

Novel Polyimide/Silica Nanohybrids from Water Glass

Summary Polyimide/silica hybrid materials were prepared via a novel sol-gel route using silicic acid oligomer (SAO) extracted from water glass. The decomposition temperatures of the hybrid samples were higher than pure polyimide. The transparency of the hybrid films could be maintained at up to 40 wt.-% silica content with the addition of -aminopropyltriethoxysilane (APTES). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results confirmed the formation and dispersion of nanometer-scale size of inorganic particles within polyimide matrix with APTES. The coefficients of thermal expansion (CTEs) of the hybrid films were lower than pure polyimide and decreased with the increasing content of silica.     

Polyurethaneurea–silica nanocomposites: Preparation and investigation of the structure–property behavior

Nanocomposites consisting of thermoplastic polyurethane–urea (TPU) and silica nanoparticles of various size and filler loadings were prepared by solution blending and extensively characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermal analysis, tensile tests, and nanoindentation. TPU copolymer was based on a cycloaliphatic diisocyanate and poly(tetramethylene oxide) (PTMO-2000) soft segments and had urea hard segment content of 20% by weight. TPU/silica nanocomposites using silica particles of different size (29, 74 and 215 nm) and at different loadings (1, 5, 10, 20 and 40 wt. %) were prepared and characterized. Solution blending using isopropyl alcohol resulted in even distribution of silica nanoparticles in the polyurethane–urea matrix. FTIR spectroscopy indicated strong interactions between silica particles and polyether segments. Incorporation of silica nanoparticles of smaller size led to higher modulus and tensile strength of the nanocomposites, and elastomeric properties were retained. Increased filler content of up to about 20 wt. % resulted in materials with higher elastic moduli and tensile strength while the glass transition temperature remained the same. The fracture toughness increased relative to neat TPU regardless of the silica particle size. Improvements in tensile properties of the nanocomposites, particularly at intermediate silica loading levels and smaller particle size, are attributed to the interactions between the surface of silica nanoparticles and ether linkages of the polyether segments of the copolymers.     

Preparation of alumina/carbon nanotubes composites by chemical precipitation

Continuous alumina coating on multi-walled carbon nanotubes (MWCNTs) was successfully prepared by a new method of chemical precipitation using aluminum nitrate and ammonia as starting materials. Structure and morphology of the alumina/multi-walled carbon nanotubes (Al₂O₃/MWCNTs) composites were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), infrared spectra (IR), thermo gravimetric analysis (TG), differential thermal analysis (DTA) and N₂ adsorption–desorption. The results show that polyvinyl alcohol (PVA) modification on the surface of MWCNTs contributes to form continuous alumina coating, γ-Al₂O₃ layers with thickness of 1–3 nm cover the surface of MWCNTs and the original structure of MWCNTs is retained during the coating process.     

多壁碳纳米管/二氧化硅纳米复合材料的制备及其吸油性能

以羧化多壁碳纳米管为基体、纳米硅溶胶粒为增强相,通过一步液相共混方法制备多壁碳纳米管/二氧化硅纳米复合材料。利用傅里叶变换红外光谱（FTIR）、电子扫描电镜（SEM）、热重（TGA）、孔结构分析（BET/BJH）对其进行了表征。以水中柴油为研究对象考察了该样品对水中柴油的吸附脱除效果,并与纳米二氧化硅胶粒、原生碳纳米管以及活性炭进行对比。结果表明：硅溶胶粒表面修饰后的多壁碳纳米管的聚团行为得以改善,而且材料具有微孔-介孔双孔道结构。对水中直馏柴油的去除率高达97.79%,并于1 h达到吸附平衡。整个吸附过程遵循准二级动力学模型,吸附体系的表观活化能为11.37 kJ·mol^-1,吸附等温线与Freundlich模型较为吻合,吸附效果明显强于其他3种吸附剂。     

Functionalized Hybrid Nanoparticles and their Interaction with Spin-Labeled Cyclodextrin

Hybrid nanoparticles of the gold@silica and magnetite@silica type were obtained by embedding gold nanoparticles (protected by captopril, average size 2.3 nm) or magnetite nanoparticles (protected by alanine, average size 10 nm) into larger silica nanoparticles (50–100 nm) using the Stober method. A silica precursor, i.e., a mixture of tetramethoxysilane and 3-aminopropyl-trimethoxysilane (in a 10/1 ratio), was used in order to facilitate the links between inner nanoparticles and the silica layer. These nanoparticles containing free amino-groups were easily functionalized with adamantane, naphtyl and nitrobenzofurazan moieties using appropriate reagents (adamantane-1-carbonylchloride, 1-naphtylisocyanate, and 7-chlor-4-nitrobenzofurazan). The hybrid nanoparticles were characterized by different means (IR and TEM) and their interaction with spin-labeled β-cyclodextrin was also studied (by EPR spectroscopy). EPR spectra show that cyclodextrins are attached to the nanoparticles surface. The hybrid nanoparticles functionalized with nitrobenzofurazan moieties have the largest interaction with the cyclodextrin cavity.     

Sol–Gel Synthesis and Microstructure Analysis of Amino-Modified Hybrid Silica Nanoparticles from Aminopropyltriethoxysilane and Tetraethoxysilane

Agglomerated amino-modified silica nanoparticles were prepared from a novel Stöber-like precursor system consisting of aminopropyltriethoxysilane (APTES), tetraethoxysilane (TEOS), ethanol, and water where the molar ratio APTES/TEOS was 0, 0.1, 1.0, and 2.0, and the molar ratio H₂O/-SiOC₂H₅ was about 20 to 60, or great excess amounts of H₂O were employed. APTES catalyzed the hydrolysis and condensation of both silanes. ²⁹Si magic angle spinning nuclear magnetic resonance spectra confirmed that the particles consisted of Qⁿ species (Si(OSi) _n (OH)_{4− n} ; n =2, 3, 4) and Tⁿ species (NH₂(CH₂)₃–Si(OSi) _n (OH)_{3− n} ; n =2, 3). The APTES content in the precursor solutions controlled the agglomerating spherical particle size and morphology: 0.1 in the ratio APTES/TEOS led to almost independent spheres of 300–400 nm, while the larger ratios 1 and 2 led to ∼250 and ∼150 nm spheres, respectively, that were largely agglomerated and some were fused to look like peanut-shells. When soaked in Kokubo's simulated body fluid, those amino-modified particles deposited apatite. The mechanisms of particle formation and apatite deposition were discussed in terms of an intraparticle hydrated layer.     

Cyclability study of silicon–carbon composite anodes for lithium-ion batteries using electrochemical impedance spectroscopy

The effects of carbonization process and carbon nanofiber/nanotube additives on the cycling stability of silicon–carbon composite anodes were investigated by monitoring the impedance evolution during charge/discharge cycles with electrochemical impedance spectroscopy (EIS). Three types of Si–C anodes were investigated: the first type consisted of Si nanoparticles incorporated into a network of carbon nanofibers (CNFs) and multi-walled carbon nanotubes (MWNTs), with annealed polymer binder. The second type of Si–C anodes was prepared by further heat treatment of the first Si–C anodes to carbonize the polymer binder. The third Si–C anode was as same as the second one except no CNFs and MWNTs being added. Impedance analysis revealed that the carbonization process stabilized the Si–C anode structure and decreased the charge transfer resistance, thus improving the cycling stability. On the other hand, although the MWNTs/CNFs additives could enhance the electronic conductivity of the Si–C anodes, the induced inhomogeneous structure decreased the integrity of the electrode, resulting in a poor long term cycling stability.     

Thermally and mechanically enhanced epoxy resin‐silica hybrid materials containing primary amine‐modified silica nanoparticles

In this article, a series of hybrid materials consisted of epoxy resin matrix and well‐dispersed amino‐modified silica (denoted by AMS) nanoparticles were successfully prepared. First of all, the AMS nanoparticles were synthesized by performing the conventional acid‐catalyzed sol–gel reactions of tetraethyl orthosilicate (TEOS), which acts as acceded sol–gel precursor in the presence of 3‐aminopropyl trimethoxysilane (APTES), a silane coupling agent molecules. The as‐prepared AMS nanoparticles were then characterized by FTIR, ¹³C‐NMR, and ²⁹Si‐NMR spectroscopy. Subsequently, a series of hybrid materials were prepared by performing in situ thermal ring‐opening polymerization reactions of epoxy resin in the presence of as‐prepared AMS nanoparticles and raw silica (RS) particles (i.e., pristine silica). AMS nanoparticles were found to show better dispersion capability in the polymer matrices than that of RS particles based on the morphological observation of transmission electron microscopy (TEM) study. The better dispersion capability of AMS nanoparticles in hybrid materials was found to lead enhanced thermal, mechanical properties, reduced moisture absorption, and gas permeability based on the measurements of thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and gas permeability analysis (GPA), respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008