含氟丙烯酸酯共聚物表面性能的稳定化研究

为提高传统含氟丙烯酸酯乳胶膜表面性能的稳定性,以γ-(甲基丙烯酰氧基)丙基三甲氧基硅烷(MPS)作为可交联单体,采用细乳液聚合法合成了MPS改性的含氟丙烯酸酯共聚物,利用DLS、TEM、IR对聚合物进行表征,研究了MPS对合成乳液的稳定性、涂膜性能和膜表面接触角稳定性的影响。结果表明,细乳液聚合法适合用于对水敏感单体的聚合,合成的纯丙烯酸酯乳胶为球形结构,平均粒径为92 nm,而氟丙乳胶和含3%MPS的含硅氟丙乳胶形成了典型的核壳结构,平均粒径分别增大至107 nm和103 nm,含硅氟丙聚合物中存在Si-O-Si的交联结构。涂膜性能测试表明,MPS的引入增加了共聚物膜的硬度、耐溶剂性和耐水性。接触角测试表明,随MPS用量的增加,乳胶膜对水的初始接触角和动态接触角随时间的降低值均呈先增大后减小的趋势,共聚体系中加入适量MPS,通过含氟链段与MPS链段的协同作用,可显著提高涂膜表面性能的稳定性。     

GHD室温自交联乳液的聚合及贮存稳定性

采用半连续种子乳液聚合技术合成了含甲基丙烯酸缩水甘油酯(GMA)、甲基丙烯酸羟乙酯(HEMA)和甲基丙烯酸二甲氨基乙酯(DMAEMA)的室温自交联乳液(GHD).实验结果表明,在甲基丙烯酸甲酯(MMA)-丙烯酸丁酯(BA)-GMA种子乳液存在下,聚合温度升高,聚合过程稳定性下降,但乳液的贮存稳定性提高;乳化单体滴加速度加快,种子聚合物的玻璃化温度升高,可减少聚合过程的交联凝聚作用,提高聚合过程的稳定性;而HEMA和DMAEMA用量增加对聚合过程的稳定性没有明显影响,但使乳液的贮存稳定性下降.官能团间的交联凝聚作用可能是影响室温自交联乳液聚合及贮存过程稳定性的关键因素.     

反应性乳化剂存在下的五元苯丙乳液共聚合

采用反应性乳化剂SE-10N,通过正交实验及单因素实验确定了以苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸和丙烯腈为单体的五元无皂苯丙共聚乳液的组成及聚合工艺。所制得的无皂乳液稳定,其乳胶粒大小均匀,粒径为50~60nm,比同组成的有皂乳液乳胶粒的粒径稍小。乳液涂膜透明、硬度达H级;其硬度、耐水性及钙离子稳定性均较同组成有皂乳液的好。     

马来酸类可聚合乳化剂及其在乳液聚合中应用

使用可聚合乳化剂可以很好地解决传统乳化剂的缺点,提高乳液的应用性能.马来酸类乳化剂其可聚合基团反应活性适中,可以很好地键合在乳胶粒表面上,且更为突出的是这类乳化剂不易发生均聚,而是倾向于与单体发生共聚.研究表明,马来酸类可聚合乳化剂应用到乳液聚合中,可以改善乳胶液的性能,提高乳胶膜的耐水性等.文章介绍了这一类新型的乳化剂,并根据其亲水基团进行了分类,分别介绍其合成路线,总结了马来酸类乳化剂的特点,概述了在常见乳液聚合体系中的应用与研究.     

氧化-还原低温引发甲基丙烯酸甲酯/丙烯酸丁酯超浓乳液聚合研究

以乳化剂十二烷基硫酸钠 (SDS)和共乳化剂十六烷醇 (HD)作为复合乳化体系 ,过氧化二苯甲酰(BPO)和N ,N 二甲基苯胺 (DMA)作为氧化还原引发体系 ,甲基丙烯酸甲酯 丙烯酸丁酯 (MMA BA)作为混合单体 ,制备了分散相占 83 %以上的稳定的超浓乳液 ,然后在低温下引发聚合 .探讨了引发剂浓度、氧化剂与还原剂的摩尔比、乳化剂的浓度、液膜增强剂的种类、聚合温度等因素对聚合稳定性和聚合速率的影响 ,测定并计算得到了聚合速率的公式 ;用激光散射粒度分布仪测定了聚合物乳胶粒子的大小及粒径分布 ,用透射电子显微镜观察了聚合物乳胶粒的形态 ,讨论了乳化剂浓度、聚合温度等对乳胶粒形态、大小的影响     

马来酸类可聚合乳化剂的合成及其在细乳液聚合中的应用

采用三步法合成了可聚合乳化剂马来酸单十六醇酯丙基磺酸钠.并用正交实验法优化了马来酸单十六醇酯合成工艺条件,结果表明反应的最佳条件为:催化剂质量分数1%,反应时间3.0h,反应温度90℃,马来酸酐与十六醇的摩尔比1.1:1.苯乙烯-丙烯酸丁酯细乳液聚合使用该乳化剂与传统乳化剂相比,在较低温度下(65℃)具有较高的转化率,且所得乳液具有较好的电解质稳定性,乳胶膜的耐水性也得到提高.     

PU-St超浓乳液聚合动力学及聚合物性质的研究

采用一步法制备聚氨酯预聚体 ( PU)苯乙烯 ( St)超浓乳液 ,探讨了稳定的超浓乳液的 NCO/OH和 St/PU最佳比例范围。研究了乳化剂和引发剂浓度对超浓乳液聚合的稳定性及聚合动力学的影响 ,并制得了用 PU改性的聚苯乙烯 ( PS)粉状树脂。测定了乳胶粒子大小、粒径分布、分子量和聚合物膜的动态力学性质。发现乳胶粒子大小及其单分散性随聚合转化率的增加而增加 ;与本体聚合比较 ,聚合物的分子量有明显增大 ;PU- PS复合聚合物具有优良性能。     

室温自交联型聚丙烯酸酯纳米乳液的研究

本文分别用反应性乳化剂和常规乳化剂合成了室温自交联丙烯酸纳米乳液,并对其乳液的流变性能进行了研究,发现:反应性乳化剂所得乳液的表观粘度ηa、稠度系数K、零剪切粘度η0均比常规乳化剂所得乳液的增大。并用XPS对乳胶膜进行分析表明,反应性乳化剂在乳液的干燥成膜过程中不易向胶层表面迁移富集。与常规乳化剂体系的乳液相比,反应性乳化剂体系的乳液挥发速率快,吸水率低。并对两种乳液进行了粒径大小及分布的表征。     

氧化还原低温引发MMA/BA超浓乳液薄层共聚合的研究

以甲基丙烯酸甲酯-丙烯酸丁酯(MMA-BA)作为混合单体、以乳化剂十二烷基硫酸钠(SDS)和共乳化剂十六烷醇(CA)作为复合乳化剂体系、聚乙烯醇(PVA)为液膜增强剂,制备了稳定的超浓乳液.以过氧化二苯甲酰(BPO)和N,N′-二甲基苯胺(DMA)为氧化还原引发体系,用一种新的超浓乳液薄层技术,在较低温度下引发共聚合.探讨了液膜增强剂种类和聚合环境对聚合稳定性影响;研究了薄层厚度,薄层面积,聚合温度和加热方式对体系(包括单体和水)挥发性和转化率的影响.比较了薄层和试管聚合的速率.用透射电子显微镜观察了水浴与烘箱加热方式下聚合物乳胶粒的形态,得到了在水浴中反应后的聚合物粒子平均粒径和分散度都减小的结果.     

改性丙烯酸乳液合成及性能研究

通过核壳乳液聚合法合成了烷基丙烯酸酯磷酸酯改性的丙烯酸乳液,讨论了聚合温度、乳化剂、磷酸酯的加入方式和用量、pH值等因素对乳液合成以及涂膜性能的影响。结果表明:聚合温度控制在75～80℃之间较为合适,使用了烷基丙烯酸酯磷酸酯进行改性的乳液,单体转化率和固含量提高,凝胶率以及涂膜吸水率明显下降,乳液的稳定性得到提升。当聚合温度为78℃,磷酸酯占单体总质量0.5%(wt)、反应体系pH值在5左右以及采用延后滴加磷酸酯单体的方式时,能够提高乳液耐水等性能以及涂膜的交联度,合成性能优异的磷酸酯改性丙烯酸乳液。     

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%.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.