近红外光谱法快速测定聚乙烯醇的醇解度

应用傅里叶变换近红外漫反射光谱技术,通过对光谱预处理方法的选择和模型优化,建立了准确度较好的聚乙烯醇醇解度近红外定量分析模型,并验证了其可行性。通过验证试验表明,其预测值接近于化学法测定值,适合聚乙烯醇醇解度快速测定。     

非极性有机溶剂对分子内氢键弱化程度的单分子力谱定量研究

利用单分子力谱技术, 以3种不同醇解度的聚乙烯醇(PVA)为模型体系, 定量研究了非极性有机溶剂对分子内氢键强度的影响. 3种PVA样品在非极性有机溶剂中的分子内氢键强度均约为其在真空中强度的48%. 结果表明, 非极性有机溶剂对分子内氢键的弱化作用十分显著, 可削弱其约50%的本征氢键强度. 本文研究结果提示人们需重新审视液相环境对高分子单链弹性和非共价相互作用的影响.     

聚丙烯片晶厚度对受限空间内聚丁烯-1三方晶型形成的影响

当聚丁烯-1以小液滴的形式分散在另一种树脂基体中时,会表现出不同的成核路径,即发生“分级结晶”现象.前期研究结果表明将聚丁烯-1以≤20%的比例与聚丙烯进行共混,动力学优先的晶型Ⅱ的成核会受到抑制,使得聚丁烯-1小液滴相界面处更容易发生界面诱导成核形成三方的晶型Ⅰ’.本工作采用自成核与调控聚丙烯等温结晶温度的方法,改变了聚丙烯/聚丁烯-1界面处聚丙烯的片晶厚度,发现聚丙烯的片晶越厚,晶型Ⅰ’的结晶速率越慢,进一步证明了三方晶的形成是由界面处聚丙烯诱导得到.原位广角X射线衍射结果显示,聚丁烯-1的晶型Ⅰ’是否发生重结晶取决于体系中是否存在晶型Ⅱ晶核.纯净的晶型Ⅰ’在升温过程中会直接熔融而不会转化为晶型Ⅱ.     

水溶性聚合物改性水泥的研究：Ⅱ.水溶性聚合物对水泥水化过程的 …

从聚合物改性水泥的水化速率，水化热及水化生成物三方面讨论了聚合物对水泥水化的影响。水泥溶液ｐＨ值和电导率及水泥凝结时间的研究结果表明，非离子聚合物聚丙烯酰胺，聚乙烯醇减慢水泥的初期水化，具有缓凝作用，而阴离子聚合物水解聚丙烯酰胺，聚丙烯酸，磺化聚丙烯酰胺及磺化聚苯乙烯则加速水泥的初期水化，具有促凝作用；     

多规格产品的PVA低碱醇解新工艺

对比了制备聚乙烯醇的高碱醇解法与低碱醇解法技术特点;在低碱法皮带醇解工艺的基础上,进行多项技术改进、设备改造,形成醇解新工艺;醇解新工艺可同时生产不同聚合度和醇解度的多规格高品质PVA产品,节能效率提供好,带来更可观的经济效益。     

电场条件下高分子共混物组分浓度梯度化的研究

研究了聚乙烯醇/聚丙烯酸高分子共混物水溶液中,共混物各组分在电场诱导条件下沿电场方向的浓度梯度分布情况.通过测定不同时刻PVA/PAA高分子共混物水溶液在电场的不同区域内的pH值,研究了电场诱导下共混物各组分沿电场方向的迁移过程.结果表明,PAAn-向电场正极迁移,同时由于浓差梯度,PVA向负极迁移,并形成浓度梯度分布.随时间的延长,高分子共混物的组分梯度程度逐渐加大.     

γ射线辐照后乙烯基聚合物的电磁共振研究

辐照后的聚氯乙烯及聚丙烯腈的电磁共振研究,发现随着温度升高(低于高分子的玻璃化温度或熔点)自旋浓度迅速下降.连同聚氯乙烯辐射交联产率小而自旋浓度大于聚乙烯的事实,提出了高分子在辐照时电子被高分子基团俘获而形成负离子的假说.应用这假说能说明一系列高分子辐射化学现象:如溶剂对高聚物的辐射效应影响;低温辐射离子聚合历程;辐照后高分子导电性增加等问题.     

用UV-Vis法研究聚乙烯醇水溶液的透明度

用紫外可见分光光度计(UV-vis)测试了聚乙烯醇(PVA)水溶液和盐溶液的透明度,研究了PVA醇解度、电解质和温度对PVA溶液透明度的影响.实验结果表明,UV-Vis法是一种简便可行的测定PVA溶液透明度的方法.     

高分子量聚乙烯醇增强冰的研究

以本体光聚合法制备的高分子量聚乙烯醇(HMWPVA)为增强剂,考察了增强冰的力学性能.当HMWPVA的浓度为3%(质量分数)时,增强冰的拉伸强度、断裂伸长率、压缩强度和压缩模量分别为普通冰的11.7,3.5,2.3和2.1倍.对比试验发现PVA分子量对冰的拉伸性能影响较大,对冰的压缩性能影响较小.此外,在室温29℃时纯冰的融化时间为5 min,而4%HMWPVA增强冰的融化时间长达240 min.     

丙烯酰基苯并三氮唑及其聚合物光物理过程的研究

1-N-丙烯酰基苯并三氮唑(ABT)及其聚合物-聚丙烯酰基苯并三氮唑(PABT)作为功能高分子材料的母体和重要原料已引起人们的重视。如报道[1]利用PABT可制备聚丙烯酸及其各种不同的酯类、带芳酰胺或脂肪酰胺侧基的各种聚酰胺化合物等。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.