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实验探究题是近年广东高考的热点题型,其情境新颖、取材广泛、考查灵活,具有探究性、开放性及灵活性等特点。实验探究题以化学实验为基础,考查实验方案设计是其重点。同时,它对探究教学也具有导向、激励和评价等功能。 相似文献
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两性离子聚合物因独特的链结构,使其具有卓越的化学性能、良好的热稳定性与水化性能,尤其是具有"反聚电解质效应溶液行为"这一特点,近年来引起了广泛关注。因大多数两性离子聚合物链内引入了—OH,—COOH,—SO3H等亲水基团,使其具有抗蛋白质污染、抗细菌黏附及抗凝血等性能。迄今为止,人们已合成了很多新型的、功能化的两性离子聚合物并将其应用于石油工业、生物医用材料、药物合成和污水处理等各个领域。本文主要对两性离子聚合物的结构、性质、合成方法、应用、最新研究成果及发展前景等作了简单的概述和分析,并对它的合成方法和应用作了主要介绍,以期对两性离子聚合物的研究和发展有所借鉴。 相似文献
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罂粟籽为罂粟的种籽,作为药用,主要用果汁及壳,具有止痛、镇咳等多种功效,但因其所含吗啡等生物碱具有显著成瘾性,故将其列为毒麻药品而严格管理和使用;罂粟籽则榨油供食用,具有一定的医疗保健作用。 相似文献
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《化学进展》2017,(1)
近年来纳米材料受到越来越多的关注,由于其纳米尺寸效应,纳米材料在环境修复、医药、生物工程等各个领域都有广泛的应用。纳米材料具有大的比表面积、高表面结合能等优异特性,这使其在重金属吸附领域的应用受到极大的关注。金属硫化物纳米材料属于其中一类,其作为吸附剂具有吸附速度快、吸附容量高、吸附产物稳定等优良特性,对水体和土壤基质中的重金属离子、放射性元素和有机物等表现出良好的吸附性能,具有潜在的研究和应用价值。本文综述了国内外几类金属硫化物纳米材料在吸附领域的研究进展,包括Zn S、铁硫化物、Mo S2、Cu S和其他金属硫化物及其相关复合材料,并对其未来的发展方向进行了展望。 相似文献
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聚酰胺-胺树形大分子的合成与应用 总被引:12,自引:0,他引:12
聚酰胺_胺 (PAMAM)树形大分子是一种从中心核开始增长 ,具有确定代数和末端基的新型合成高分子。由于该化合物具有高度的几何对称性、大量的端基、分子内存在空腔等结构特点 ,在催化、医药、生命科学、工业等领域具有广泛的应用前景。本文通过介绍PAMAM树形大分子的合成、表征方法及其性能研究 ,讨论了其改性研究和应用。 相似文献
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两性离子聚合物具有阴阳离子基团,能够高度水化,具有优异的生物相容性。甲基丙烯酰乙基磺基甜菜碱(SBMA)聚合物因其独特的两性离子链结构,具有抗蛋白质污染、抗细菌黏附及抗凝血等抗生物污染性能,这种特性使其在生物医学等相关领域得到越来越多的应用。本文介绍了其抗生物污染的水化理论,对甲基丙烯酰乙基磺基甜菜碱类聚合物的结构、性质、合成方法及表面构建方法等作了概述和分析,对其在人造器官材料、组织工程、生物分离、生物监测、温度敏感材料等方面的应用作了重点介绍,并分析了目前应用存在的问题和潜在的应用前景。 相似文献
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可光固化星形超支化聚酯的合成与表征 总被引:20,自引:0,他引:20
描述了基于季戊四醇和1,2,4 苯三甲酸酐,经由甲基丙烯酸缩水甘油酯和甲基丙烯酸酐改性的系列超支化聚酯的“发散”合成方法,即合成反应从“中心核”开始,逐步向外扩展,控制链增长,每个分子形成具有大约8,12和16个甲基丙烯酸酯双键的超支化臂。这种星形聚酯分子具有三维球状结构,不会产生分子链间的缠结,在辐射固化涂层和粘合剂等领域具有广阔的应用前景. 相似文献
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Heléne Magnusson Gisle Øye Wilhelm R. Glomm 《Journal of Dispersion Science and Technology》2013,34(4):547-554
A series of mesoporous aluminas have been synthesized using commercial hyperbranched polyesters of the second to fourth generation as porogens. To achieve a suitable interaction between the polymer and the aluminium source, aluminium sec‐butoxide, the terminal hydroxyl groups of the hyperbranched polymer were first reacted by succinic anhydride. The mesoporous aluminas were analyzed by nitrogen adsorption/desorption, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). No dependence of the generation of the hyperbranched template on pore size was found in this study. Instead the pore size appears to depend on the amount of water added to the reaction mixture as well as the concentration of the hyperbranched polymer. 相似文献
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以三羟甲基丙烷(TMP)为核,二羟甲基丙酸(DMPA)为支化单体,通过熔融缩聚法合成了第3代端羟基脂肪族超支化聚酯,并用十八酸对其进行端基改性,采用广角X射线衍射(WAXD)、示差扫描量热分析(DSC)及红外光谱(FTIR)研究了不同端基改性程度的超支化聚酯的结晶熔融行为及端烷烃链的构象和堆积结构随温度的变化,采用旋转流变仪研究了端烷烃链对脂肪族超支化聚酯熔体动态黏弹行为的影响.结果表明,这类改性超支化聚酯的结晶归因于长链端烷烃的有序排列,改性程度越高,衍射峰强度越大.受限结晶的端烷烃链在升温后并不能完全转变为无序的结构状态,改性超支化聚酯在"熔点"以上仍有部分有序结构存在.超支化聚酯的线性黏弹区随着端基改性程度的增大而逐渐变短,超支化聚酯的弹性逐渐增大,剪切变稀越明显.动态流变测试中所出现的现象与改性超支化聚酯中端烷烃链的受限密切相关. 相似文献
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Hans R. Kricheldorf Gesa Behnken 《Journal of polymer science. Part A, Polymer chemistry》2009,47(1):231-238
Low molar mass hyperbranched polyesters were prepared by polycondensation of 1,1,1‐tris(hydroxymethyl)ethane and various dimethyl esters of aliphatic dicarboxylic acids in bulk. The usefulness of nontoxic bismuth salts as transesterification catalysts for these polycondensations was studied. The maximum conversion increased, and the reaction time decreased in the following sequence of increasing reactivity: dimethyl sebacate < adipate < glutarate < succinate. Regardless of the monomer combination, gelation occurred at conversions > 91.5%. The hyperbranched structure was proven by 1H NMR spectroscopy and the absence of cyclic elements by MALDI‐TOF mass spectrometry. Quantitative acylation of all CH2OH groups was achieved with an excess of acetic anhydride or methycrylic anhydride. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 231–238, 2009 相似文献
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合成了一系列含羟基和乙酰氧基的超支化聚酯,将4',4'二羟基-2-甲酸-三 苯基甲烷(酚酞啉)直接缩聚和将4~',4~"-二羟基-2-甲酸-三苯基甲烷进行酯 交换反应都成功得到了超支化聚酯,以PS作标准物,由GPC测得的重均分子量为 2000到8000,~13C NMR测试表明聚合物支化度略高于50%,聚酯的玻璃化转变温度 依赖于末端和侧基官能团类型,该超支化聚酯末端含有反应性官能团,具有类似线 性高分子的高的热稳定性,相比之下,由于其大分子的形状和官能团的影响,末端 为乙酰氧基的超支化聚枉费显示了优良的溶解性能,这与一般线性高分子大不相同 ,由于氢键的存在,末端为羟基的超支化聚酯的溶解性能不佳,但是酸酯显示了 优良的溶解性能,这与一般线性高分子大不相同,由于氢键的存在,末端为羟基的 超支化聚枉费的溶解性能不佳,但是酸化可破坏氢键网络,得到的超支化聚酯可深 于一般有机溶剂。 相似文献
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Ziemer A Azizi M Pleul D Simon F Michel S Kreitschmann M Kierkus P Voit B Grundke K 《Langmuir : the ACS journal of surfaces and colloids》2004,20(19):8096-8102
The influence of hyperbranched polyesters with different functional end groups on the surface tension of mixtures with an oligo(ester diol) was investigated. The temperature dependence of the surface tension of the pure components and of the mixtures was measured by a modified Wilhelmy balance technique. The results indicate that the surface tension of the pure hyperbranched polyesters strongly depends on the functionality of the end groups. The functionalization of the hydroxyl end groups by short alkyl chains (methyl, tert-butyl) reduced the surface tension depending on the degree of substitution. The surface tension of the mixtures with the hydroxyl-terminated hyperbranched polyester was slightly increased at higher concentrations of the hyperbranched polymer compared to the surface tension of the pure ester diol. On the other hand, the surface tension of mixtures could be considerably decreased using 1% of hyperbranched polyester polyols partially substituted with short alkyl chains. In that case, the modified hyperbranched polyesters act as surface active agents. On the molecular level, the enrichment of the modified hyperbranched polyester in the surface region was proven by X-ray photoelectron spectroscopy measurements. 相似文献
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Jena KK Raju KV Prathab B Aminabhavi TM 《The journal of physical chemistry. B》2007,111(30):8801-8811
New types of hyperbranched polyesters were synthesized by the reaction of 2,2-bis(hydroxymethyl) propionic acid as an AB2-type monomer with pentaerythritol, trimethylol propane, or glycerol as the core moiety. The obtained globular networks were characterized by NMR and MALDI-TOF spectroscopic techniques. Molecular weights determined by MALDI-TOF were confirmed by gel permeation chromatography. Fourier transform infrared (FTIR) spectroscopy was used for the quantitative evaluation of hydrogen bonding as well as to study the structure-property relationship. To investigate the changes and types of intermolecular H-bonding interactions in hyperbranched polyesters with a variation in molecular structure, the deconvolution of FTIR spectra was carried out using Origin 6.0 software through the Gaussian curve-fitting method. Molecular simulations were performed through molecular mechanics and molecular dynamics (MD) calculations using the DISCOVER module. Cohesive energy density, solubility parameters, and surface properties of the hyperbranched polyesters were calculated. Further, vibrational analysis was computed using MD simulations for all the hyperbranched polyesters developed in this work. 相似文献
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Sanhao Ji Bernd Bruchmann Frederik Wurm Harm‐Anton Klok 《Journal of polymer science. Part A, Polymer chemistry》2012,50(1):25-34
Hyperbranched polyesters are among the most common hyperbranched polymers. One of the interesting features of hyperbranched polyesters is that they contain unreacted hydroxyl and carboxylic acid groups at the linear and terminal structural units, which can be postmodified to adjust thermal, solubility, or mechanical properties, or to prepare core–shell type architectures. This article reports on the synthesis of a novel class of hyperbranched polyesters via an A2 + B3 type Baylis–Hillman polymerization of 2,6‐pyridinedicarboxaldehyde and trimethylolpropane triacrylate. Baylis–Hillman polymerization generates highly functional polyesters that contain not only unreacted aldehyde and/or acrylate groups at the linear and terminal structural units but also chemically orthogonal vinyl and hydroxyl groups along the polymer backbone. Using 3‐hydroxyquinuclidine as the catalyst, hyperbranched polymers with number‐average molecular weights up to 7500 g/mol and degrees of branching up to 0.81 were obtained. To demonstrate the versatility of these hyperbranched polyesters to act as platforms for further derivatization, the orthogonal postpolymerization modification of the hydroxyl, vinyl, and pyridine functional moieties with phenyl isocyanate, methyl‐3‐mercaptopropionate, and methyl iodide is presented. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012. 相似文献