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金属主链高分子是一类完全以金属原子作为主链的新材料,在光电、传感、电化学储能等领域都具有重要的应用前景.但是,如何获得具有较高分子量的金属主链高分子,仍然是一个挑战.本文通过密度泛函理论计算方法,对镍金属主链高分子进行了结构优化和稳定性分析,发现随着聚合物分子量的增加,镍金属主链高分子的单点能逐渐降低,说明高分子量的金属主链高分子具有稳定的分子构型.但是,随着分子量的进一步提高,计算量显著增加,密度泛函理论计算方法收敛困难.为此,本文进一步通过Hartree-Fock计算方法对该系列镍金属主链高分子进行了分子构型优化,得到了与密度泛函理论计算结果相似的规律,并且发现当分子量超过1×104时,金属主链高分子仍然具有较高的结构稳定性.此外,这种电子离域在整个金属主链上的独特金属-金属的相互作用有利于实现电荷的高效传输;以金属原子为重复单元的分子结构,有望实现金属和高分子材料性能的有效结合,可以获得较高的热失重温度和熵弹性. 相似文献
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《高分子学报》2020,(7)
通过芳香族亲核取代反应合成了一系列含硅氧烷基元主链结构的半芳香族共聚酰胺.研究发现,共聚酰胺具有较高的分子量和较窄的分子量分布.硅氧烷结构的引入不仅赋予了共聚酰胺低的吸水率,而且使其能保持良好的力学性能,当硅氧烷结构含量为10 mol%时,拉伸强度达到80.0 MPa,缺口冲击强度为4.8 kJ/m~2,可与商品化HTN产品相媲美.阻燃性能测试结果可知,在不添加磷、卤等传统阻燃剂的情况下,随着硅氧烷结构含量的增加,共聚酰胺表现出良好的阻燃抗熔滴效果.当共聚酰胺中硅氧烷结构含量为10 mol%时,极限氧指数可达33.5%,可通过UL-94垂直燃烧V-0级. 相似文献
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一些高分子金属催化剂能够在常温常压下催化烯烃的加氢反应,具有很高的催化活性和选择性,而且容易回收.这些高分子催化剂所用的载体是以C—C键为主链的有机高聚物.Semikolenov等曾制备过以二氧化硅为载体的有机硅高聚物—金属络合物,即二氧化硅—聚-β-氰乙基硅氧烷—钯络合物作为烯烃的加氢催化剂,但是它的催化活性很低.我们曾经报道过二氧化硅—聚-γ-氰丙基硅氧烷—钯络合物,简写为[SiO_2— 相似文献
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通过硅氢加成反应, 以ABx型功能化β-环糊精大单体为原料, 采用一步法合成出新型超支化聚(β-环糊精)高分子. ABx大单体由单取代对甲苯磺酰化β-CD依次与烯丙基胺、1,1,3,3-四甲基二硅氧烷(含氢双封头)及丙烯酰氯反应得到. 采用1H NMR, 13C NMR, 29Si NMR和飞行时间质谱对ABx大单体及其聚合物的结构进行了表征. 利用凝胶渗透色谱/多角度激光光散射(SEC/MALLS)联用仪得到了超支化聚(β-环糊精)的分子量、分子量分布及本体黏度. 相似文献
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通过Monte Carlo 模拟方法对加核自缩合乙烯基体系在分批投料模式下的聚合行为进行研究, 考察了引发核的加入时间及分批投料方式对超支化高分子的重均分子量及多分散指数的影响. 研究结果表明, 不同的分批投料方式对超支化高分子的重均分子量和多分散性具有显著的调控作用. 通过调整投料方式、 投料次数、 引发核官能度和转化率等因素, 可以得到分子量较高且多分散性较好的超支化高分子. 相似文献
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针对由RBf型环形高分子和ABg型单体构成的环基高分子缩聚体系,从环基高分子的尺寸分布导出相应的高分子矩,进而给出环基高分子的数均分子量和重均分子量以及多分散指数等物理量.在此基础上,集中探讨了两类反应物的摩尔比、环形高分子的官能度及聚合度(分子量)对环基(环基链状和环基支化)高分子性质的影响.鉴于环形高分子对环基高分子相关特征的贡献可以发生主次转变,进而根据其数均分子量得到发生转变的反应程度.结果表明,环基高分子的多分散指数随着环形高分子官能度的增加而单调降低,但与反应物的摩尔比无关,而表征环形高分子贡献发生逆转的反应程度则与其官能度、聚合度及反应物的摩尔比密切相关.相关研究可为阐明环基高分子缩聚反应体系的统计特征提供有益的线索. 相似文献
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Handke M Kowalewska A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(4):749-757
Preparation of ceramics by sol-gel method has been known for many years, but recently it has been developed as a method for the synthesis of nanostructural ceramic materials. Hydrolytic polycondensation of simple molecules [e.g. most widely used tetraethoxysilane (TEOS)] leads to xerogel materials that can contain macromolecules of distinct random, ladder and cage or partial cage structure. In order to obtain well-defined silsesquioxanes it is preferred to start the process with more complex molecules, bringing in a specific framework that can govern the structure of the product. In the presented work alkoxy derivatives of cyclosiloxanes and polysiloxanes as well as a hydride derivative of octahedral silsequioxane (T(8)(H)) were applied as precursors in the process of hydrolytic polycondensation. Depending on the reaction conditions, silsesquioxane macromolecules or silica material of ordered structure were obtained. We have prepared mesoporous organiosilica materials without using any template or surfactant whatsoever. The meso-pores are created due to the unique structure of initial oligosiloxane or silsequioxane molecules and the specific interactions in the used catalyst/solvent system. In the case of octasilsesquioxane precursor, the condensation process gives directly mesoporous silica material. Dried polysilsesquioxanes were heated at the temperature of 600°C in argon or air atmosphere (pyrolysis or ceramization). In the atmosphere of argon SiC(x)O(y) glass materials were obtained. 相似文献
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Aluminum oxide coated cellulose fibers were modified, by an impregnation procedure, with n-propylpyridinium chloride silsesquioxane polymer. Good adherence of the polymer to the surface of modified cellulose fibers was obtained due to the Al-O-Si bond formation. The metal X-ray mapping showed that aluminum oxide and the silsequioxane polymer (Al and Si mapping) are highly dispersed on the fiber's surface. The ion exchange capacity of the material, determined on basis of exchangeable chloride ions, was 1.1 mmol g-1. The adsorption isotherms of FeCl3, CuCl2, and ZnCl2 from ethanol solutions were determined for each metal. The adsorption capacities were (in mmol g-1): FeCl3 = 0.82, CuCl2 approximately ZnCl2 = 0.37. The metal ions are adsorbed as anionic complex species by the following equilibrium reaction: + MCln right arrow over left arrow Copyright 1999 Academic Press. 相似文献
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Caihua Ni Guangjun Zhu Changping Zhu Bolong Yao D. N. T. Kumar 《Colloid and polymer science》2010,288(10-11):1193-1200
Inorganic/polymer hybrid star-shaped block copolymer nano-micelles were synthesized. In the synthetic route, multi-hydroxyl polyhedral oligomeric silsequioxane(POSS-(OH)32) was employed as the starting molecule to initiate ring-opening polymerization of d,l-lactide. 2-(Dimethylamino)ethyl methacrylate was found to polymerize at the end of polylactic acid chains, following mechanism of atom transfer radical polymerization. The well-defined star block copolymer core–shell nano-micelles were finally obtained. The structures of the copolymer and the micelles were characterized extensively. The micelles exhibited a regular spherical shape with an average diameter of 170 nm which was confirmed by transmission electron microscopy and dynamic laser scattering. The sizes of both the core and the shell were controlled by adjusting the feed ratios during the syntheses. The micelles demonstrated pH- and temperature-sensitive behaviors. 相似文献
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Augustine BH Hughes WC Zimmermann KJ Figueiredo AJ Guo X Chusuei CC Maidment JS 《Langmuir : the ACS journal of surfaces and colloids》2007,23(8):4346-4350
The effect of a remote oxygen plasma on nanocomposite hybrid polymer thin films of poly[(propylmethacryl-heptaisobutyl-polyhedral oligomeric silsequioxane)-co-(methylmethacrylate)] (POSS-MA) has been examined by advancing contact angle, X-ray photoelectron spectroscopy (XPS), and variable-angle spectroscopic ellipsometry (VASE). Exposure to a 25 W remote oxygen-containing plasma was found to convert the surface of POSS-MA films from hydrophobic to hydrophilic within 20 s. The exposure time needed for this conversion to occur decreased as the O2/N2 ratio in the plasma environment increased, indicating a positive correlation between the hydrophilicity and the presence of oxygen in the plasma. Local bonding information inferred from high-resolution XPS data showed that the isobutyl bonding to the POSS moiety is replaced with oxygen as a result of plasma exposure. Finally, VASE data demonstrates that increasing the weight percent of POSS in the copolymer significantly impedes the oxygen plasma degradation of POSS-MA films. On the basis of these results, a model is presented in which the oxygen plasma removes isobutyl groups from the POSS cages and leaves a SiO2-like surface that is correspondingly more hydrophilic than the surface of the untreated samples and is more resistant to oxidation by the plasma. The ability to modify surfaces in this manner may impact the utility of this material for biomedical applications such as microfluidic devices in which the ability to control surface chemistry is critical. 相似文献
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《Analytical letters》2012,45(14):2859-2871
ABSTRACT A polymer coated graphite rod ion selective electrode for saccharin was constructed and evaluated for the determination of saccharin in artificial table top sweeteners. The polymer consists of a thin film of silsesquioxane 3-n-propylpyridinium chloride. The electrode response was based on the ion pair formed between saccharinate and the 3-n-propylpyridinium cation from the silsequioxane polymer. The electrode exhibits a Nernstian response for saccharin concentrations between 6.9×10-6 and 5.3×10-3 mol L-1 and a detection limit of 5.5×10-6 mol L-1. The electrode response for saccharin was fast (10-20 s) and the potential independent of pH in the range of 3 to 7. The selectivity coefficients K A, B pot for several anions usually present in commercial table top sweeteners were determined following the IUPAC recommendations. The potentiometric method with the ion selective electrode was validated by the HPLC reference method, through t8543226 determination of saccharin in commercial samples of table top sweeteners. The ion selective electrode is proved suitable for the routine quality control of table top sweeteners by potentiometry. 相似文献
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Synthesis,morphology, and properties of hydroxyl terminated‐POSS/polyimide low‐k nanocomposite films
Md Abdul Wahab Khine Yi Mya Chaobin He 《Journal of polymer science. Part A, Polymer chemistry》2008,46(17):5887-5896
Polyhedral oligomeric silsequioxane (POSS), having eight hydroxyl groups for the preparation of nanocomposites with polyimide (PI) was synthesized by the direct hydrosilylation of allyl alcohol with octasilsesquioxane (Q8M8H) with platinum divinyltetramethyl disiloxane Pt(dvs) as a catalyst. The structure of allyl alcohol terminated‐POSS (POSS‐OH) was confirmed by FTIR, NMR, and XRD. A high performance, low‐k PI nanocomposite from pyromellitic dianhydride (PMDA)‐4,4'‐oxydianiline (ODA) polyamic acid cured with POSS‐OH was also successfully synthesized. The incorporation of POSS‐OH into PI matrix reduced dielectric constant of PI without loosing mechanical properties. Furthermore, the effects of POSS‐OH on the morphology and properties of the PI/POSS‐OH nanocomposites were investigated using UV–vis, FTIR, XRD, SEM, AFM, transmission electron microscope (TEM), TGA, and contact angle. The homogeneous dispersion of POSS particles was confirmed by SEM, AFM, and TEM. The nanoindentation showed that the modulus increased upon increasing the concentration of POSS‐OH in PI, whereas the hardness did not increase very much with respect to loading of POSS, due to soft‐interphase around POSS molecules in the resulting nanocomposites. Overall results demonstrated the nanometer‐level integration of the polymer and POSS‐OH. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5887–5896, 2008 相似文献
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Synthesis of poly(HEMA‐co‐AAm) hydrogels by visible‐light photopolymerization of aqueous solutions containing aspirin or ibuprofen: analysis of the initiation mechanism and the drug release 下载免费PDF全文
María Lorena Gómez Antonela Gallastegui Mariana B. Spesia Hernán A. Montejano Roberto J. Williams Carlos M. Previtali 《先进技术聚合物》2017,28(4):435-442
Recently, we reported the synthesis of hydrogels by visible‐light photopolymerization of 2‐hydroxyethylmethacrylate and acrylamide, employing safranine O as sensitizer, and a functionalized silsequioxane (SFMA) as co‐initiator/crosslinker. The influence of the ionic character of a drug on its release rate from the hydrogels was also reported. In the present study, we analyzed the photoinitiation mechanism, the synthesis of hydrogels in the presence of aspirin (ASA) or ibuprofen (Ibu), and their release from hydrogels synthesized with variable SFMA concentrations. Concerning the photoinitiation mechanism, we found that the main contribution was the electron transfer reaction between the excited triplet state of safranine and SFMA, followed by a fast proton transfer reaction from secondary amine groups. The generated nitrogen radicals initiated the copolymerization reaction. The photoreaction quantum yield was 0.031. Concerning the drug‐release study, we found that the release rate of both drugs increased by increasing pH from 7 to 10. This was ascribed to the increase in the partial ionization of the carboxylic acid groups, a fact that reduced the interactions with the secondary amine groups present in SFMA and increased the release rate. The effect was larger for ASA than for Ibu. Increasing the amount of SFMA increased both the crosslink density and the fraction of H‐bonds formed with the drugs. At pH 10, the increment in the crosslink density was dominant for the release of Ibu while the increase in fraction of H‐bonds determined the release rate of ASA. Cytotoxicity studies showed that these materials did not exhibit significant hemolytic activity. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Yong Tang Jinfeng Zhuge Jihua Gou Ruey‐Hung Chen Christopher Ibeh Yuan Hu 《先进技术聚合物》2011,22(10):1403-1413
In this study, a hybrid nanopaper consisting of carbon nanofiber (CNF) and polyhedral oligomeric silsequioxane (POSS) or cloisite Na+ clay, has been fabricated through the papermaking process. The hybrid nanopaper was then coated on the surface of glass fiber (GF) reinforced polymer matrix composites through resin transfer molding (RTM) process. The morphologies of the hybrid nanopaper and resulting nanocomposites were characterized with scanning electron microscopy (SEM). It can be seen that the nanopaper had a porous structure with highly entangled carbon nanofibers and the polyester resin completely penetrated the nanopaper throughout the thickness. The thermal decomposition behavior of the hybrid nanopapers and nanocomposites was studied with the real‐time thermogravimetric analysis/ flourier transform infrared spectrometry (TGA/FTIR). The test results indicate that the addition of pristine nanoclay increased the thermal stability of the nanopaper, whereas the POSS particles decreased the thermal stability of the nanopaper. The fire retardant performance of composite laminates coated with the hybrid nanopaper was evaluated with cone calorimeter tests using a radiated heat flux of 50 kW/m2. The cone calorimeter test results indicate that the peak heat release rate (PHRR) decreased dramatically in composite laminates coated with the CNF‐clay nanopaper. However, the PHRRs of the CNF‐POSS nanopaper coated composite laminates increased. The formation of compact char materials was observed on the surface of the residues of the CNF‐clay nanopaper after cone calorimeter test. The flame retardant mechanisms of the hybrid nanopaper in the composite laminates are discussed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Cian Cummins Roisin A. Kelly Anushka Gangnaik Yordan M. Georgiev Nikolay Petkov Justin D. Holmes Michael A. Morris 《Macromolecular rapid communications》2015,36(8):762-767
The directed self‐assembly of block copolymer (BCP) materials in topographically patterned substrates (i.e., graphoepitaxy) is a potential methodology for the continued scaling of nanoelectronic device technologies. In this Communication, an unusual feature size variation in BCP nanodomains under confinement with graphoepitaxially aligned cylinder‐forming poly(styrene)‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) BCP is reported. Graphoepitaxy of PS‐b‐P4VP BCP line patterns (CII) is accomplished via topography in hydrogen silsequioxane (HSQ) modified substrates and solvent vapor annealing (SVA). Interestingly, reduced domain sizes in features close to the HSQ guiding features are observed. The feature size reduction is evident after inclusion of alumina into the P4VP domains followed by pattern transfer to the silicon substrate. It is suggested that this nanodomain size perturbation is due to solvent swelling effects during SVA. It is proposed that using a commensurability value close to the solvent vapor annealed periodicity will alleviate this issue leading to uniform nanofins.