环二硅氮烷-聚硅氧烷共聚物高温气相色谱固定相的研究

含苯基的环二硅氮烷聚硅氧烷共聚物(TMCDPS)主链上含有刚性结构,具有良好的耐热性能。将此材料用作毛细管气相色谱固定相,考察该固定相的柱效、极性、热稳定性,并对石蜡、聚乙烯裂解产物、原油等样品进行色谱分析。实验结果表明:该固定相有着良好的分离效果,属于中等极性固定相,其最为突出的特点就是在聚硅氧烷主链上引入大分子基团,使得其耐温性能大大提高,温度达到400℃时,柱流失量依然不高。     

阴离子疏水缔合共聚物/阳离子蠕虫状胶束协同增粘自组装网络

将阴离子疏水缔合丙烯酰胺共聚物P(NaAMC14S-b-AM)与阳离子蠕虫状胶束十六烷基三甲基溴化铵/水杨酸钠(CTAB/NaSal)在水溶液中自组装制备了新型的缔合增粘体. 由稳态剪切和动态流变实验结果得出: 自组装体系在80 ℃下仍具有显著的协同增粘效应, 其流变行为符合Maxwell模型. 同蠕虫状胶束相比, 自组装体系的稳态模量G0、力学松弛时间τR和缠结点密度ν都有增加, 由此分析缔合体系中两组分间形成了相互缠结的网络结构, 在链缠结处共聚物主链上的疏水侧链嵌入到了蠕虫状胶束的内核.     

低分子量结晶性丙交酯/乙交酯与己内酯/乙交酯共聚物热转变温度的组成与分子量依赖性

以1,4-丁二醇为引发剂、辛酸亚锡为催化剂,通过L-丙交酯(LLA)、乙交酯(GA)、ε-己内酯(CL)的开环共聚,制得了低分子量的端羟基结晶性LLA/GA共聚物(PLLGA)和CL/GA共聚物(PCG),分别以FTIR1、H-NMR、GPC、DSC对其微结构和热转变温度进行了表征,重点考察了其热转变温度的组成、分子量依赖性.结果表明,利用辛酸亚锡/二元醇引发开环聚合,通过改变单体配比和单体/引发剂配比,可方便地调控共聚物的组成和分子量;通过改变共聚物的组成和分子量,可在较宽的范围内调节共聚物的热转变温度,并得到了玻璃化温度和熔点与组成、分子量之间定量的经验关系式.     

聚氨酯弹性体的相区相容性和阻尼性能研究

合成了一系列含有不同软段的聚氨酯嵌段共聚物及接枝共聚物,并测试了其动态力学性能,结果表明,聚氨酯共聚物的相容性与大分子的链结构有关,接枝链的存在对聚氨酯嵌优共聚物相空性和阻尼性能有很大影响。     

超临界CO2中苯乙烯RAFT分散聚合

以末端带有三硫代碳酸酯的聚二甲基硅氧烷(PDMS-TTC)为大分子链转移剂,在超临界CO2中通过苯乙烯的可逆加成-断裂链转移(RAFT)聚合制备了聚二甲基硅氧烷-b-聚苯乙烯(PDMS-b-PS)嵌段共聚物,对聚合反应动力学以及产物的组成、分子量和形貌等进行了表征.由于PDMS链段可溶于超临界CO2而PS链段不溶,因此在超临界CO2中制备PDMS-b-PS嵌段共聚物的过程是以嵌段共聚物自身作为分散稳定剂的RAFT分散聚合,产物为粒径较均一的球形颗粒.     

聚乙烯醇水溶液反复冷冻过程中的溶剂化效应

采用示差扫描量热技术(DSC)对聚乙烯醇(PVA)水溶液反复冰冻过程中的溶剂化效应进行研究.引入水化数的概念来表征溶剂化效应的大小.结果表明不同浓度区间的PVA水溶液其在反复冰冻过程中溶剂化效应显著不同,主要归因于高分子链分子内和分子间缠结程度对溶剂分子"参与"溶剂化的程度和方式的不同.作者把极稀高分子溶液的研究结果拓展到高分子稀溶液或亚浓溶液区间,阐述了高分子溶液中高分子链的物理图像.冷冻次数的增加导致链间缠结增加,部分溶剂则被包裹在由链间缠结点所形成的网圈内成为分子链的一部分.溶液溶剂化程度的变化受到包裹溶剂与高分子链脱溶剂化的综合影响.     

RAFT聚合制备氟硅嵌段共聚物及结构性能

以三硫代酯封端的聚二甲基硅氧烷作为大分子链转移剂,通过可逆加成-断裂链转移聚合(RAFT)制备了一系列聚二甲基硅氧烷-b-聚甲基丙烯酸十二氟庚酯(PDMS-b-PDFHMA)二嵌段共聚物.利用凝胶渗透色谱(GPC)、傅里叶变换红外光谱(FT-IR)、氢核磁共振谱(1H-NMR)对该嵌段共聚物的组成、结构和分子量进行了表...     

RAFT法合成两亲性嵌段共聚物PSt-b-PAA-b-PSt及其在离子液体[BMIM][PF_6]中的自组装

用三硫代碳酸二(α,α′-二甲基-α-乙酸)酯(BDATC)作为链转移剂,苯乙烯St作为第一单体,通过可逆加成-断裂链转移聚合(RAFT)方法合成出大分子链转移剂PSt-CTA,以丙烯酸AA作为第二共聚单体合成出3个不同嵌段比的两亲性嵌段共聚物聚苯乙烯-b-聚丙烯酸-b-聚苯乙烯(PSt-b-PAA-b-PSt).通过傅里叶变换红外光谱(FTIR)和核磁共振氢谱(1H-NMR)确定了PSt-b-PAA-b-PSt结构,使用凝胶渗透色谱(GPC)测定了大分子引发剂PSt-CTA和嵌段共聚物PSt-b-PAA-b-PSt的分子量及分子量分布.将这3个不同嵌段比的两亲性嵌段共聚物在离子液体1-丁基-3-甲基咪唑六氟磷酸盐[BMIM][PF6]中进行自组装,用透射电子显微镜(TEM)观察聚合物在离子液体中自组装结构.研究发现,当PSt的链段长度固定时,胶束的自组装形态主要依赖于PAA链的长度.当PAA链段较长时,胶束呈球形;PAA链段变得较短时,胶束的形态则由球形转变为核壳结构,并且胶束形态在25℃至100℃之间不受温度影响.     

催化链转移聚合制备接枝型两亲共聚物及其溶液性质研究

采用大分子单体法制备接枝型两亲共聚物, 通过表面张力仪、偏光显微镜、旋转流变仪和小角X射线衍射研究了两亲共聚物在水溶液中的聚集行为及其相结构. 首先末端带有可聚合双键的聚甲基丙烯酸叔丁酯大分子单体(PtBMA Macromonomer)通过催化链转移聚合法制备, 所用到的催化链转移剂为二水合双(二氟化硼苯二酮肟)合钴(II) (COPhBF). 然后将所得到的大分子单体与丙烯酸正丁酯(BA)进行自由基共聚得到接枝共聚物PBA-g-PtBMA, PBA-g-PtBMA中PtBMA的侧链部分在酸性条件下定量水解成聚甲基丙烯酸(PMAA)并用NaOH中和得到主链疏水侧链亲水的接枝型两亲共聚物PBA-g-P(MAA^－Na^＋). 用Wilhelmy吊片法研究了不同浓度的两亲共聚物水溶液的表面张力, 发现其行为与小分子表面活性剂不同. 同时用动态光散射法测量了两亲共聚物水溶液中聚集体的粒度, 发现在研究的浓度范围内(0.02～10 g/L)聚集体都存在两个粒度分布峰(约30和300 nm). 浓溶液(w＝37.5%)的偏光显微照片呈现层状液晶的特征图案, 而流变研究表明此时体系具有明显的粘弹性, 说明体系形成了层状液晶. 并且用小角度X射线衍射测定了层状液晶的层间距, 约为12.6 nm.     

“活”的α-甲基苯乙烯共聚物:聚合反应新化学和材料工程新技术

高于临界聚合反应温度时,α-甲基苯乙烯(AMS)单体和其聚合物处于聚合-解聚平衡.基于AMS聚合物在受热时可裂解生成大分子链自由基的特性,提出了含AMS结构单元的共聚物是一种"活"的,可作为大分子自由基引发剂的概念,并通过实验对AMS共聚物的引发性能和应用进行了研究.首先,合成了AMS与(甲基)丙烯酸酯类单体、丙烯酸、苯乙烯和马来酸酐等的共聚物.然后以上述共聚物为大分子引发剂,在90℃引发(甲基)丙烯酸酯类单体和苯乙烯等的本体聚合、溶液聚合和乳液聚合,得到了嵌段共聚物.用ESR谱证明了AMS的共聚物在加热时能裂解生成以碳原子为中心的大分子链自由基.此外,在聚合物的熔融共混中,AMS分解产生的大分子链自由基通过偶合反应形成接枝链,原位生成相容剂.AMS共聚物还可以对碳纳米管及无机粒子进行表面原位接枝改性.AMS共聚物是一类无小分子残留的绿色自由基引发剂,可以用于低成本制备两嵌段共聚物,也可以用于聚合物的熔融共混增容.     

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.