细乳液法合成单核核壳结构氧化硅/聚苯乙烯复合微球

采用细乳液聚合法,以3-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)表面改性的直径50nm的氧化硅粒子为核,在乳化剂、助乳化剂、引发剂存在的情况下制备了小粒径、单核核壳结构氧化硅/聚苯乙烯纳米复合微球.研究表明,苯乙烯的浓度、超声细乳化时间,是制备这种小粒径、单分散、单核核壳结构的氧化硅/聚苯乙烯纳米复合微球的关键因素.透射电镜(TEM)的观察显示,在优化的实验条件下,可以制得平均粒径95nm,壳厚20nm,粒径均一、球形规整度较好、单核核壳结构的氧化硅/聚苯乙烯纳米复合微球.其平均粒径远低于用其它聚合方法制备的复合微球.     

Deposition of electrically conductive ceria/polypyrrole nanocomposite particles on flexible polyethylene naphthalate film via in situ photo-induced polymerization

To achieve a flexible and transparent conductive film via a simple method, ceria/polypyrrole nanocomposite particles were coated on Piranha-treated polyethylene naphthalate (PEN) film as the flexible substrate. Photo-induced polymerization was carried out by cerium (III) nitrate hexahydrate dissolved in acetonitrile and irradiation by UV wavelengths for 2 h. The effect of Piranha treatment on deposition of the conductive nanocomposite particles was examined. Deposited PEN samples prepared at various conditions were characterized using FESEM, AFM and STM, UV–vis spectroscopy, four-probe conductivity and contact angle measurements. Adhesion quality of the deposited nanoparticles was investigated by Scotch-tape test.     

Preparation and characterization of polyaniline/cerium dioxide (CeO2) nanocomposite via in situ polymerization

Crystalline ceria (CeO₂) nanoparticles have been successfully synthesized by a microwave-assisted solution method. Polyaniline (PANI)/cerium dioxide (CeO₂) nanocomposite was synthesized by in situ polymerization of aniline in the presence of CeO₂ nanoparticles. Characterization of CeO₂ and PANI/CeO₂ nanomaterials are carried out using various studies such as powder X-ray diffraction, infrared spectral and UV–Vis absorption spectral analyses, scanning electron microscopic and high-resolution transmission electron microscopic (HRTEM) studies and thermal analysis. The HRTEM of the images indicate that the CeO₂ nanoparticles were embedded in the PANI matrix forming the core–shell structure.     

New mesoporous silica/carbon composites by in situ transformation of silica template in carbon/silica nanocomposite

Hard template-based fabrication of mesoporous carbon unavoidably goes through the removal process of the template to generate template-free carbon replica, including troublesome disposal of template waste often accompanied by toxic etchant, which not only increases the fabrication cost of materials but also raises serious environmental concerns. As a novel strategy to overcome such problem, a direct in situ synthesis approach using silica waste in carbon/silica nanocomposite as a silica source and cetyltrimethylammonium bromide as a porogen under basic condition is reported in this study for the generation of a new composite composed of mesoporous MCM-41 silica and hollow carbon capsule. The resultant MCM-41/carbon capsule composite offers a 3-D interconnected multimodal pore system, which discloses a wide pore range of ordered uniform mesopores (ca 2.3?nm) resulting from MCM-41 silica and disordered uniform mesopores (ca 3.8?nm) and macropores (ca 300?nm) from hollow mesoporous carbon, respectively. The composite has a high specific surface area (ca 909?m²/g) and large pore volume (ca 0.73?cm³/g). The in situ transformation approach of silica waste into valuable mesoporous silica is considered as a promising scalable route for efficient new multi-functional composites useful for a wide range of applications such as adsorption of volatile organic compounds and radioactive wastes produced in a nuclear facility.     

Preparation and characterization of polyimide/silica nanocomposite spheres

Silica (SiO₂) nanocomposite spherical particles coated with polyimide had been synthesized by a dispersion polymerization method. The chemical structure of polyimide/silica (PI/SiO₂) nanocomposite spherical particles was investigated by using FT-IR, and the surface morphology characterization was performed with SEM. The TEM showed that SiO₂ core was surface-coated with a multilayer composite and the multilayer thickness was about 20 nm. Moreover, the particles were homogeneously distributed and interconnected very fine. Basing the results, it was found that the PI/SiO₂ nanocomposite particles were core–shell structure.     

Intercalation behavior and enhanced dewaterability of waste sludge of cationic polyacrylamide/montmorillonite composite synthesized via in situ intercalation polymerization

Montmorillonite was rendered organophilic with acryloxyethyl dodecyl dimethyl ammonium bromide (denoted as OMMT-AD), and a series of cationic polyacrylamide (CPAM)/OMMT-AD composites were synthesized via an in situ intercalation polymerization. It was found that with increasing AD content, the interlayer spacing of OMMT and the thickness of the intercalated AD chains increased, and the saturation content of AD molecules in the MMT layers was 2.0 CEC. Some orderly structures of AD molecules formed between the MMT layers, and MMT was proposed to present lateral-monolayer, lateral-bilayer and paraffin-type monolayer conformations in the confined space of MMT. The cationic degree and reduced viscosity of the CPAM/OMMT-AD composites decreased with the increase of the OMMT-AD content. The strong intermolecular interaction appeared between the CPAM and the OMMT-AD, and the OMMT-AD platelets dispersed well with an exfoliated state in CPAM matrix as indicated by X-ray diffraction analysis and TEM observation. Compared with solution intercalation, the composites prepared by in situ intercalation polymerization had better stability and dispersion of MMT in the CPAM matrix. The dewaterability of the waste sludge was improved by using CPAM/OMMT-AD composites.     

聚乙二醇/聚丙烯酰胺相变材料的制备及性质研究

通过在丙烯酰胺的聚合反应中加入聚乙二醇(PEG)的方法制备了聚乙二醇/聚丙烯酰胺(PEG/PAM)相变材料,并对材料的相变行为、分子间的相互作用和相转变实质进行了研究.结果表明,PEG/PAM相变材料的相变温度、相变焓不仅随着PEG分子量的减小而降低,而且随着PEG质量分数的减小而降低;PEG与PAM间存在一定的分子间氢键,致使相变材料在PEG的熔点以上表现出固体化行为;相变材料发生固-固相变的实质是,在升温时材料中的PEG由结晶态变成了无定形态.     

一步原位聚合法制备电泳显示微胶囊的研究

用一步原位聚合法制备了电泳显示微胶囊.考察了系统调节剂、搅拌、壁材用量对微胶囊的粒径分布及其形貌的影响.实验结果表明,在搅拌速度为700r/min,pH值为1.5～2.0条件下,以明胶作为系统调节剂,脲醛树脂作为壁材,可以制得具有透明囊壁的球形微胶囊,粒径分布在20～70μm之间.采用合适的壁材用量可以获得高紧密度的囊壁.该法制备的微胶囊可望在电泳显示材料中有较好的应用.     

An exfoliated polyamide-6/layered double hydroxide nanocomposite via in situ intercalative polymerization between positively charged inorganic platelets

An exfoliated polyamide 6 (PA6)/layered double hydroxide (LDH) nanocomposite has been successfully prepared via an in situ intercalative polymerization procedure. The original LDH surface is hydrophilic. After an ion exchange reaction of LDH with sodium stearate (SS), the organic anions intercalated into the interlayer space of LDH, adopting a double-layer inclined structure, and the surface of the organic-modified LDH became hydrophobic. An exfoliated PA6/LDH nanocomposite has been obtained via in situ intercalative polymerization. Its microstructure was characterized by a combination of wide-angle X-ray diffraction (WAXD) and transmission electron microscopic (TEM) techniques. The positively charged inorganic platelets of LDH were dramatically exfoliated and homogeneously dispersed in the PA6 matrix.     

原位聚合法制备纳米凹凸棒土/聚乳酸复合材料

将凹凸棒土（AT）进行提纯和有机改性后, 采用原位聚合法制备了OAT质量分数为1%、 3%、 5%的纳米凹凸棒土/聚乳酸复合材料（OAT/PLA-x）。采用红外、 扫描电镜、 X射线衍射等对复合材料进行了表征, SEM结果表明, 凹凸棒土粒子在复合材料中实现了均匀稳定分散。复合材料的力学性能和综合热性能测试表明: OAT/PLA-3复合材料的拉伸强度、 弹性模量分别比纯PLA增加98.6%和130.0%; 复合材料的热稳定性明显提高。同时, 复合材料的溶液降解速率也明显加快。      

蒙脱土负载引发剂法制备PMAA/MMT纳米复合材料

将引发剂过硫酸钾(KPS)负载在MMT片层上制得负载型引发剂MMT-KPS-1和MMT-KPS-2.进而引发甲基丙烯酸(MAA)聚合制备聚甲基丙烯酸/蒙脱土(PMAA/MMT)纳米复合材料.采用X射线衍射(XRD)、热重分析(TG)、热分析(DTA)分别对负载引发剂和纳米复合材料进行表征.结果表明,KPS进入MMT的片层间,并且负载引发剂(MMT-KPS-1)的引发活性较KPS有所提高;所制备的PMAA/MMT纳米复合材料属于剥离型纳米复合材料,应用于皮革鞣制所得坯革的湿热稳定性、增厚率、抗张强度、撕裂强度都有所提高,鞣后浴液中铬含量显著降低.     

聚丙烯酰胺/氧化石墨纳米复合材料的研究

氧化石墨具有良好的层状结构，其层间具有丰富的官能团，能与有机聚合物形成插层纳米复合材料进而改善材料的性能．采用层离吸收-原位聚合法制备了聚丙烯酰胺／氧化石墨纳米复合材料，并采用XRD、HREM及DSC等对其结构和性能进行了表征。结果表明，聚丙烯酰胺与氧化石墨两者之间存在着较强的相互作用，材料的玻璃化转变温度得到提高，层离吸收-原位聚合法是获得聚丙烯酰胺／氧化石墨层纳米复合材料的有效途径，聚丙烯酰胺在氧化石墨中存在着多种排列方式，不同层间距(1．6nm和2．8nm)的聚丙烯酰胺／氧化石墨纳米复合结构同时存在。     

One-step synthesis of conductive ceria/polypyrrole nanocomposite particles via photo-induced polymerization method

Inorganic–organic nanocomposites of ceria/polypyrrole with core/shell morphology and median diameter about of 150 nm in single nanoparticles were synthesized by a novel one-step photo-polymerization method using cerium (III) nitrate hexahydrate dissolved in acetonitrile and irradiation under UV wavelengths for 2 h. The photo-polymerization products were characterized using high resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, wide-angle X-ray diffraction, particle size analysis, and field emission scanning electron microscope. Crystalline/amorphous structure was detected for the obtained core/shell nanoparticles via selected area electron diffraction pattern. Electrical conductivity of the nanoparticles was measured by four-probe technique.     

Polyethylene/palygorskite nanocomposites with macromolecular comb structure via in situ polymerization

Polyethylene/palygorskite nanocomposites with “macromolecular comb” structure were prepared via in situ polymerization. The TiCl₄ catalyst was first loaded on the surface of the nanoscale whiskers of palygorskite. Subsequently the ethylene was introduced into the reaction system, and the polyethylene molecular chain was generated directly at the surface of the palygorskite whiskers. As a result, a polyethylene molecular chain with “macromolecular comb” structure was generated. The product thus obtained was blended with regular polyethylene to make a polymer blend, which was characterized by transmission electron microscope (TEM). Finely dispersed palygorskite whiskers in polyethylene matrix were found, which resulted in the improvement of mechanical strength of the polymer blends. Compared with regular polyethylene, the impact strength and tensile strength of the polymer blend were improved by 63.5% and 21.3% respectively at 25°C, when the palygorskite content of the nanocomposite was 20 wt%.     

Preparation and microwave absorbing properties of nickel-coated carbon fiber with polyaniline via in situ polymerization

Electric conductive and microwave absorbing material PANI/Ni/CF was prepared by in situ polymerization of polyaniline on the surface of nickel-coated carbon fiber (Ni/CF). The morphologies and structures of CF, Ni/CF, PANI and PANI/Ni/CF were characterized by scanning electron microscope and X-ray diffraction. Results show that the CF was wrapped tightly around the nickel layer, and the Ni/CF was coated by PANI. Measurement of four probes resistance tester indicates that the electrical conductivity of PANI/Ni/CF was great improved compared with PANI and PANI/CF. Vibrating sample magnetometry shows that the magnetic saturation intensity of Ni/CF and PANI/Ni/CF was 13.8 and 2.3 emu/g, respectively. According to the vector network analyzer, the microwave absorbing properties of PANI/Ni/CF were better than those of PANI and PANI/CF, and its minimum loss value is ?12.4 dB at 8.8 GHz.     

In situ polymerization of l-Lactide in the presence of fumed silica

Chemiorheology, i.e. rheological changes during the polymerization, of a biosourced monomer, i.e. l-Lactide, containing fumed silica have been studied. For that purpose, the reaction was proceeded in situ between the plates of a dynamic rheometer. The polymerization kinetics was followed from the variation of the complex shear modulus versus reaction time. Moreover, at temperatures lower than the crystallization temperature, it was possible to follow the crystallization process while the polymerization takes place. Adding fumed silica particles into the monomer leads to the formation of a physical (percolated) network from particle–particle interactions, i.e. silica, in the l-Lactide probably hydrophilic interactions. The gel-like structure was kept while the polymerization as long as the strain remains low indicating that the silica particle network remains weak. Furthermore, the mechanism of the break down of the gel structure under large deformation as well as the recovery was discussed. It seems that the non-linearity effect of the nanocomposites stems in the silica inter-particle interactions. It was found that silica particles do not have any effect on the temperature of crystallization – molar mass relation but could act as nucleating agent.In situ polymerization of l-Lactide in the presence of 5 wt.% of modified fumed silica was carried out in a reactor. It was found that fumed hydrophilic silica leaded to a microcomposite with highly dense agglomerates in the polymer matrix whereas with a less hydrophilic silica it was possible to decrease the size of the agglomerates increasing the dispersion. The finest dispersion state was achieved with the “initiating” functionalized silica leading to a “grafting from” polymerization of the l-Lactide. Such functionalized silica leads to a nanoscale dispersion in a one-step bulk polymerization with only a few small agglomerates.     

Synthesis of silver/silica nanocomposites anchored by polymer via in situ reduction

Silver/silica nanocomposites were synthesized by in situ reduction of silver salt and anchorage of the formed silver nanoparticles to silica nanospheres using a polymer anchor. Synthesis conditions including reductants, anchor polymers, and surfactants were determined. The successful formation of the nanocomposites was governed by the reduction of silver nitrate in citrate aqueous solution by sodium borohydride and adsorption onto polyvinylpyrrolidone coated silica nanospheres. The size and structure of the nanocomposites were observed by light scattering measurement and scanning electron microscopy, respectively. Optical properties of the nanocomposites were determined by UV-visible absorption spectra.     

Viscoelasticity of polyethylene/montmorillonite nanocomposite melts

Observations are reported on low-density polyethylene melts reinforced with montmorillonite nanoclay at concentrations of filler ranging from 0 to 10 wt.% in small-amplitude shear oscillatory tests, start-up tests with a constant strain rate, and relaxation tests. Constitutive equations are derived for the time-dependent response of a nanocomposite melt at three-dimensional deformations with finite strains. The model accounts for (i) inhomogeneity in the distribution of nanoparticles, (ii) non-affinity of an equivalent polymer network with sliding junctions, and (iii) evolution of energies of inter-chain interaction driven by orientation of clay platelets. It is demonstrated that the stress–strain relations correctly describe the experimental data and adjustable parameters change consistently with nanoclay content.     

Organic–inorganic hybrids obtained by in situ polymerization of aniline in silica/phosphonate matrix

A method for preparing organic–inorganic hybrids containing organophosphorus compounds, silica, and polyaniline (PANI) was developed using sol–gel technique. This method allows the in situ synthesis of organic–inorganic hybrids by reacting tetraethoxysilane (TEOS), aniline, initiator, organophosphorus compound in formic acid. The formic acid has multiple functions: as solvent and acidic media for polymerization of aniline and reagent for sol–gel process. The use of an organophosphorus compound as coupling agent and the introduction of a conductive polymer in silica matrix was investigated.