二氧化硅空心球的制备及研究

在乙醇/水的混合溶液中,采用聚乙烯吡咯烷酮（PVP）为分散剂,偶氮二异丁腈（AIBN）为引发剂,通过分散聚合法制备出聚苯乙烯（PS）微球。然后以微球为模板,PS粒子作为核,SiO_2作为壳,在600℃时经过热分解得到SiO_2空心球。通过热分析仪、扫描电子显微镜对制得的空心球进行了表征和分析,并讨论其影响因素。     

Corrosion performance of waterborne epoxy coatings containing polyethylenimine treated mesoporous-TiO2 nanoparticles on mild steel

Waterborne epoxy coatings were modified by adding mesoporous-TiO₂ nanoparticles (meso-TiO₂). In order to achieve proper dispersion of meso-TiO₂ in the epoxy-based coating and make possible chemical interactions between meso-TiO₂ and polymeric coating, meso-TiO₂ was treated with polyethylenimine (PEI) of various molecular weights. Corrosion performance of mild steel coated specimens was investigated employing electrochemical impedance spectroscopy (EIS) and salt spray test. Coatings with meso-TiO₂/PEI (600 molecular weight) possessed the best corrosion performance among the coating specimens. The EIS results showed that the resistance value of coating with meso-TiO₂/PEI (600 molecular weight) was above 9.87 × 10⁷ Ω cm² which was higher than neat epoxy coating. Possible chemical interactions between polymeric matrix and treated nanoparticles caused high barrier properties and high degree of cross-linking.     

介孔中空二氧化硅及硅基微球制备研究进展

介孔中空材料有特定孔道结构,具有中空、密度小、比表面积大的特点,因而具有较好的渗透性、吸附性、筛分分子能力和光学性能,成为具有广泛应用前景的热点研究材料。详细地介绍了国内外新型功能材料介孔中空二氧化硅及硅基微球主要制备方法,包括表面沉积法、层层组装法、原子转移自由基聚合法、喷雾法、微乳液法。同时介绍了合成的介孔、中空二氧化硅和硅基微球的形貌特点及应用。指出不同方法、不同制备条件对材料的形貌、孔径大小、孔形状及材料晶形有很大影响,条件温和、步骤简单、环境友好的制备方法是发展趋势。     

PLA–PEG‐grafted hollow magnetic silica microspheres as the carrier of iodinated contrast media

In this work, hollow magnetic silica microspheres (HMS) were synthesized by the template method, polyethylene glycol (PEG) and poly(lactic acid) (PLA)‐grafted hollow magnetic microspheres HMS@PLA–PEG were successfully prepared through ring‐opening polymerization method. Ioversol was loaded into HMS@PLA–PEG by physical coating, and the drug loading content was up to 39.4%. It also exhibited a slower and steady release than HMS and the cumulative release was up to 55.1% at physiological pH, which implied the PLA–PEG could prolong the circulation time. Meanwhile, to improve the efficiency of contrast, we have developed composite microspheres encapsulating superparamagnetic iron oxide (Fe₃O₄) as magnetic target for increasing the local concentration of the contrast media and expecting to put magnetic resonance imaging (MRI) and computed tomography (CT) technology together to apply in medical applications. Furthermore, the cytotoxicity assay in vitro was also investigated. The results revealed the ioversol‐loaded HMS@PLA–PEG exhibited low toxicity at a higher concentration, even it is up to 400 μg/mL. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44914.     

聚乙烯亚胺/多巴胺改性氧化硅固定碳酸酐酶

利用聚乙烯亚胺（PEI）/多巴胺（DA）共沉积法改性氧化硅，并以此为载体固定化碳酸酐酶（CA）。考察了PEI/DA质量比、沉积时间对沉积率的影响，用傅里叶红外光谱（FTIR）和扫描电子显微镜（SEM）对改性前后的微球进行了表征；研究了沉积率、载体用量、酶浓度及戊二醛（GA）浓度对固定化酶活回收率的影响；考察了固定化酶的储存稳定性和重复利用性。结果表明，随PEI/DA质量比增加，沉积率先增加后降低，质量比为1∶1时最大；随沉积时间增加，沉积率线性增长，10 h后PEI/DA体系沉积率为单独DA沉积改性的2.66倍，但沉积时间对N元素含量和酶活回收率影响不大；酶固定化时载体用量存在饱和值，CA和GA浓度的最优值分别为0.8 mg/ml和0.1%(质量)，此时酶活回收率可达78.8%。在25℃下储存30 d后，固定化酶的保留活性为77.2%，而游离酶只有12%；重复使用10次后，固定化酶仍能保持88.3%的相对活性。     

Template-free synthesis of uniform hollow silica nanoparticles for controllable antireflection coatings

Antireflection coatings consisting of nanoparticles have promising applications in a wide range of UV optical fields, such as high-power laser systems and space telescopes. However, an open question for these coatings is how to minimize light scattering caused by the nanoparticles. Here, we utilize hollow silica nanoparticles to realize antireflection coatings, which largely diminish light scattering and, hence, exhibit excellent transmission even at UV wavelengths. The hollow silica nanoparticles were synthesized using a template-free approach and then dip coated onto fused silica substrates to form antireflection coatings. The coatings were found to exhibit nearly 100% transmission at any wavelength ranging from the UV to IR bands by variation of the coating thickness. Moreover, the coatings showed relatively high environmental stability because their hollow structures were insensitive to contaminants. This study provides a novel route to fabricate UV antireflection coatings with improved optical properties and good environmental stability, which will help promote the understanding, design and fabrication of optical coatings.     

气溶胶辅助自组装制备中空球形二氧化硅材料的机理及应用

以正硅酸乙酯（TEOS）和甲基三乙氧基硅烷（MTES）为混合硅源,不同配比条件下采用气溶胶辅助自组装技术制备高比表面积的中空介孔二氧化硅纳米颗粒（HMSNs）,并应用于原花青素（PC）的负载,以期提高其生物利用度。利用扫描电镜（SEM）、透射电镜（TEM）、X射线衍射（XRD）、红外图谱（FTIR）和粒径分析（DLS）等对载体颗粒的形成过程、结构特性以及负载性能进行探究,基于BET分析方法计算HMSNs的比表面积,并对孔径分布进行分析。结果表明,前体溶液水解的活性中间体缩合形成二氧化硅网络结构,同时雾化后的气溶胶液滴在径向浓度梯度自组装成球形结构,水解-缩合与自组装过程协同作用促进了分散性良好的介孔二氧化硅（MSNs）的形成。经退火处理、纯化操作去除模板剂NaCl和表面活性剂十六烷基三甲基溴化铵（CTAB）,最终获得具有中空结构的HMSNs。当TEOS/MTES的摩尔比为60/40时,HMSNs具有极大的比表面积（1083m²/g）和较大的孔容积（0.37cm³/g）,其孔径主要分布在2~4nm之间,PC在HMSNs上的负载量可达30.7mg/g。     

Effect of silica nucleants on the rates of crystallization of poly(ethylene terephthalate)

Studies of the crystallization of poly(ethylene terephthalate) (PET) by d.s.c., both isothermally and non-isothermally, show that the addition of silica causes marked increases in rate at loadings < 1 part filler in 100 parts polymer. At higher loadings the overall rate of crystallization decreases until it becomes less than that of un-nucleated PET. Modified silica, with an alkoxy-coated surface, causes similar but less pronounced changes in rate. The retardation in rate inspite of an increase in the number of spherulites is attributed to an increase in the viscosity of the polymer melt due to strong adsorption onto the silica particles.     

Kinetics and equilibrium of cobalt ion adsorption on cross‐linked polyethylenimine membrane

The kinetics and equilibrium of cobalt ion adsorption on crosslinked polyethylenimine (PEI) membrane were studied by the spectroscopic method in terms of time, cobalt ion concentration, and temperature. It was found that the adsorption of cobalt ion on crosslinked PEI membrane obeyed the pseudofirst‐order kinetic model and the equilibrium adsorption amount of cobalt ion on crosslinked PEI membrane was closely related to the initial cobalt ion concentration. The equilibrium adsorption amount increased with the decrease of temperature and obeyed a Langmuir isotherm to give the equilibrium constant for the adsorption of cobalt ion on crosslinked PEI membrane under various temperatures. Based on Van't Hoff equation the enthalpy and entropy of the adsorption of cobalt ion on crosslinked PEI membrane were determined to be ?12.9 kJ mol^?1 and ?107 J mol^?1 K^?1, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of silica surface treatment on the impregnation process of silica fiber/phenolics composites

Effects of silica surface treatment on the impregnation process of silica fiber/phenolics composites were studied. Micro‐Wilhelmy method was used to evaluate the surface characterization of silanized silica fibers. The interlaminar shear strength (ILSS) measurements and the void contents of the silica fiber/phenolics composites were also performed. The interactions occurring between silica fiber and the components of phenolic resin solution can affect the contact angle between silica fiber and phenolic solution and the dynamic adsorption behavior of phenolic resin onto silica fiber. There are competitive adsorptions to different extent for phenolic resin and solvent onto silica fibers. Silica fibers as reinforcement treated by silane‐coupling agent, such as γ‐aminopropyl‐triethoxysilane, γ‐glycidoxypropyl‐trimethoxysilane, trimethylchlorosilane, and γ‐methacryloxypropyl‐trimethoxysilane, influence the mechanical interfacial properties of silica fiber/phenolics composites and the uniformity of resin distribution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

表面活性剂对二氧化硅空心微球结构的影响

分别在阳离子和阴离子两种不同类型表面活性剂的存在下,用正硅酸乙酯(TEOS)为硅源包覆纳米尺度的碳酸钙颗粒,去除表面活性剂和碳酸钙,得到了二氧化硅空心微球。用TEM、XRD及低温氮吸附等测试手段对这类材料进行了表征,研究了表面活性剂对样品结构的影响。结果表明,在合成中加入表面活性剂,使二氧化硅空心微球的球壳上出现了介孔相,改善了样品的孔结构。空心微球的BET比表面积为399～898m2/g,明显高于未加表面活性剂的样品。     

Architecture of colloidal crystals constructed by silica hybrid nanoparticles

Silica (SiO₂)‐crosslinked polystyrene (PS) particles possessing photofunctional N,N‐diethyldithiocarbamate (DC) groups on their surface were prepared by the free‐radical emulsion copolymerization of a mixture of SiO₂ (diameter D_n = 192 nm), styrene, divinyl benzene, 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC), and 2‐hydroxyethyl methacrylate with a radical initiator under UV irradiation. In this copolymerization, the inimer VBDC had the formation of a hyperbranched structure by a living radical mechanism. These particles had DC groups on their surface. Subsequently, poly(methyl methacrylate) brushes encapsulated SiO₂ particles were synthesized by the grafting from a photoinduced atom transfer radical polymerization (ATRP) approach of methyl methacrylate initiated by SiO₂‐crosslinked PS particles as a macroinitiator. We constructed the colloidal crystals using these photofunctional particles. Moreover, the SiO₂ particle array of colloidal crystals was locked by radical photopolymerization with vinyl monomer as a matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of the oxidation temperature on the structure and properties of polyacrylonitrile‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of the oxidation temperature of the PAN hollow fiber precursor on the microstructure, specific surface, pore size distribution, and adsorption properties of PAN‐based activated carbon hollow fiber (PAN‐ACHF) were studied. When PAN hollow fibers were oxidized at 270°C, because of drastic oxidation, chain scission occurred, and the number of pores within and on the surface of the resultant PAN‐ACHF increased, but the pores were just in the thinner region of the skin of PAN‐ACHF. The surface area of PAN‐ACHF reached a maximum when the oxidation temperature was 270°C. The adsorption ratios to creatinine were all higher than 90% at all oxidation temperatures, and the adsorption ratio to VB₁₂ reached a maximum (97%) at 230°C. The dominant pore sizes of the mesopores in PAN‐ACHF ranged from 2 to 5 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 203–207, 2005     

两性离子型聚电解质的合成及对二氧化硅分散性能

以甲基丙烯酰氧乙基二甲基胺(DM)与1,3-丙磺酸内酯为原料合成了3-(2-甲基丙烯酰氧乙基二甲氨基)丙磺酸盐(DMAPS)。以过硫酸铵为引发剂、次亚磷酸钠为链转移剂,在水溶液中进行DMAPS本体自由基聚合,制备了两性离子型聚电解质(PDMAPS),并将其用作二氧化硅分散剂。利用FTIR、1HNMR以及GPC对DAMPS和PDAMPS进行分析与表征,并通过单因素实验和正交实验研究了不同反应条件对聚电解质分散性能的影响。为了使分散的二氧化硅达到最低的黏度和粒径,最优的制备条件如下:反应温度为75℃、反应时间为3 h、引发剂加入量为单体质量的1.0%,在该条件下制备的PDMAPS分散性能最佳,当其掺量为0.8%(质量分数)时,粒径分析表明其二氧化硅中值粒径(d50)从21.193μm降低到0.449μm。     

Effect of compatibilizer on the dispersion of untreated silica in a polypropylene matrix

BACKGROUND: A new processing method for polypropylene–untreated precipitated silica (PP/SiO₂) composites based on the incorporation of a second polymer phase of polyamide 6 (PA6) is presented and compared with a more classic one making use of compatibilizers: glycerol monostearate (GMS), ethylene acrylic acid ionomer (IAAZE) and maleic anhydride grafted polypropylene (MA‐graft‐PP). The effects of processing methods and conditions on the microstructure and properties of PP/SiO₂ composites prepared by melt compounding are investigated with a view to reduce the size of aggregates of silica from the micrometre to the nanometre scale and to improve the link between filler and matrix. RESULTS: On the one hand, the presence of GMS and IAAZE compatibilizers significantly improves the dispersion of the silica particles. On the other hand, when using a PA6 second phase, the SiO₂ particles are dispersed in PA6 nodules. Within these nodules, SiO₂ appears dispersed at the nanoscale but with larger particles (‘aggregates’) of about 200 nm. Significant improvements in tensile strength and modulus are obtained using MA‐graft‐PP compatibilizer. An increase in impact strength is observed in the case of GMS compatibilizer. Thermal parameters indicate also that silica plays the role of nucleation agent for PP matrix. All improvements (tensile strength, modulus and impact strength) increase with the addition of compatibilized PA6 second phase. CONCLUSION: By the incorporation of masterbatch of silica in PA6 as a second polymer polar phase, a successful new production method for PP/SiO₂ nanocomposites has been developed. Interestingly, this method does not require any (expensive) pre‐treatment of the silica. Copyright © 2007 Society of Chemical Industry     

Effects of oxidation time on the structure and properties of polyacrylonitrile‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of oxidation time of PAN hollow fiber precursor on the microstructure, specific surface, pore size distribution, and adsorption properties of PAN‐based activated carbon hollow fiber (PAN‐ACHF) were studied in this work. Both of specific surface area and adsorption ratio to VB₁₂ reach maximums when PAN hollow fibers are oxidized for 5 h in air. The adsorption ratios for creatinine are all higher than 90% over all oxidation time. After 5 h of oxidation, the number of pores on the surface obviously increases, and the pore size is uniform. After 7 h of oxidation, the number of macropores in PAN‐ACHF increases. The dominant pore sizes of mesopores in PAN‐ACHF range from 2 to 5 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of activation temperature on the properties and structure of PAN‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation temperature of a precursor fiber on the microstructure, specific surface, pore‐size distribution, and adsorption properties of PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. After the activation process, the BET surface area of the PAN‐ACHF and surface area of mesopores in the PAN‐ACHF increased very remarkably and reached 1422 m² g^?1 and 1234 m² g^?1, respectively, when activation temperature is 1000°C. The adsorptions to creatinine and VB₁₂ of PAN‐ACHF were much high and reached 99 and 84% respectively. In PAN‐ACHF which went through the activation at 700°C and 800°C, the micropore filling mainly occurred at low relative pressures, multimolecular layer adsorption occurred with the increasing of relative pressure, and the filling and emptying of the mesopores by capillary condensation occurred at high relative pressures. But in PAN‐ACHF which went through the activation at 900°C, a mass of mesopores resulted in the large pore filling by capillary condensation. The dominant pore sizes of mesopores in PAN‐ACHF are from 2 nm to 5 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3778–3783, 2006     

Degradable poly(ester amine) based on poly(ethylene glycol) dimethacrylate and polyethylenimine as a gene carrier

Degradable poly(ester amine) (PEA) based on poly(ethylene glycol) dimethacrylate (PMEG) and polyethylenimine (PEI) were synthesized by Michael addition reaction. The ratios of PEI to PMEG in PEAs were 0.99, 1.02, and 1.07 with corresponding number‐average molecular weight of 1.3 × 10⁴, 1.2 × 10⁴, and 0.9 × 10⁴, respectively. Degradation rate of PEA at pH 7.4 was higher than that at pH 5.6. Good plasmid condensation and protection ability was shown when N/P molar ratio of PEA to DNA was above 15 (N: nitrogen element in PEA, P: phosphate in DNA). PEA/DNA complexes had positive zeta potential, narrow size distribution, good dispersity, and spheric shape with size below 250 nm when N/P ratio was above 30, suggestion of their endocytosis potential. Compared with PEI 25 KDa, the PEAs showed essential nontoxic to HeLa, HepG2 and 293T cells. With an increase in the molecular weight of PMEG, the transfection efficiency of PEAs in HeLa, HepG2 and 293T showed a tendency to decrease as well as the percent decrease of gene transfection efficiency with serum. The mechanism of PEA‐mediated gene transfection was attributed to “proton sponge effect” of PEI in the PEA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of activation time on the properties and structure of polyacrylonitrile‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation time of a precursor fiber on the microstructure, specific surface area, pore‐size distribution, and adsorption properties of PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. The BET surface area of PAN‐ACHF and surface area of mesopores gradually increase with activation time extending, and reach the maximum values, 780 and 180 m² g^?1, respectively, when fibers are activated at 800°C for 100 min. The adsorption ratio to creatinine changes little with activation time extending and all values over all activation time are above 90%. The adsorption ratio to VB₁₂ gradually increases with activation time extending before 60 min, and then becomes relatively constant from 60 to 100 min. The number of pores on the surface of PAN‐ACHF increases with activation time extending. The amount of mesopores in PAN‐ACHF made of fibers activated for different time increases with activation time extending and the dominant pore sizes of mesopores in PAN‐ACHF range from 2 to 5 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2565–2569, 2006