单分散PS/PAA聚合物微球的研制

以苯乙烯为单体,采用分散聚合法制备了单分散性的聚苯乙烯(PS)微球,然后以PS微球作为种子、丙烯酸(AA)进行无皂种子乳液聚合制备了PS／PAA微球。考察了单体、引发剂、分散剂用量,反应介质极性和交链剂等因素对微球粒径大小及其分布的影响,探讨了分散聚合的反应机理。结果表明,通过改变反应工艺条件,能够制备粒径为1．0～3．0μm、单分散性很好的PS微球;通过无皂种子乳液聚合得到的核壳结构的PS／PAA微球粒径为2．50μm,多分散系数(PI)为0．0325,酸值为10．27mgNaOH／g,其表面带有羧基的特性能进一步扩大应用范围。     

室温沉淀聚合制备单分散聚苯乙烯微球

采用沉淀聚合的方法以乙醇/水为混合溶剂、K_2S_2O_8/NaHSO_3为引发剂,室温下引发苯乙烯聚合制备了单分散的聚苯乙烯(PS)微球.研究了反应时间、引发剂用量、反应溶剂中乙醇与水的比例、搅拌速度对聚苯乙烯微球的收率及形貌、单体转化率的影响.结果表明,聚苯乙烯微球的单体转化率、微球的收率和粒径随着反应时间的延长而增加,反应12 h后趋于稳定;当增加引发剂的用量,聚苯乙烯微球的单体转化率、微球的收率和粒径都有所增加,K_2S_2O_8与Na HSO_3用量分别在≤2.0%和1.3%时,能够得到单分散的聚苯乙烯微球;随着反应介质中水含量的增加,聚苯乙烯微球的单体转化率、微球的收率先增加后降低,单分散性变差,水含量在≤40%能够得到单分散的微球;搅拌速度从600 r/min增加到1200 r/min时,微球粒径、收率与单体转化率几乎没有变化.并初步研究了聚苯乙烯微球的形成机理.     

单分散磁性P(St/BA/MAA)微球的制备

在共沉淀法合成超细磁流体的基础上 ,以苯乙烯 (St)、丙烯酸丁酯 (BA)和甲基丙烯酸 (MAA)为共聚单体 ,在不同的介质体系中采用无皂乳液聚合法制备了单分散 ,粒径范围为 80～ 2 30nm的磁性P(St BA MAA)微球 .详细探讨了介质极性、磁流体中表面活性剂含量对磁性高分子微球粒径和单分散性的影响 .实验结果表明 ,在一定范围内随介质极性降低 ,磁性高分子微球的单分散性提高 ,随表面活性剂用量增加 ,单分散性变差 .总体来看 ,磁性高分子微球的单分散性与其表面静电斥力密切相关 ,过大或过小的静电斥力均会导致磁性高分子微球单分散性的降低 .     

沉淀聚合制备聚(季戊四醇三丙烯酸酯-苯乙烯)单分散微球及其形成机理

以季戊四醇三丙烯酸酯(PETA)作交联剂,苯乙烯作共聚单体,偶氮二异丁腈作引发剂,在乙醇或其与水的混合溶剂中沉淀聚合制备了交联聚合物微球.研究了反应时间、交联剂用量以及溶剂中水含量对聚合过程及微球的影响.结果表明当PETA用量在单体质量的5%-35%之间且反应时间不低于6h时可制得单分散聚合物微球.当PETA用量低于20%时,所得微球的粒径随PETA用量的增加逐渐减小,粒径分布逐渐变窄;此后继续提高PETA用量,微球粒径又逐渐增大,粒径分布逐渐变宽.向反应介质中加入水,可明显提高微球产率及单体转化率,但其体积分数达30%时,所得微球分散性变宽.在此基础上对微球的形成机理也进行了讨论.     

微米级PS-PEDOT核壳型导电微球的合成与拉曼表征

以分散聚合法制备的微米级聚苯乙烯(PS)微球为模板、3,4-乙烯二氧噻吩(EDOT)为单体、过硫酸铵(APS)为引发剂,通过氧化聚合制备了PS-PEDOT核壳型复合导电微球。采用扫描电镜、透射电镜等对导电微球的形貌和结构进行了表征,重点采用拉曼光谱研究了其核壳结构特征。并研究了超声分散、溶液pH以及单体配比对导电微球形貌的影响。实验结果表明:超声的引入可提高导电微球的单分散性,改善微球的形貌。随着pH的降低或单体配比的增加,导电聚合物在PS微球表面的负载量随之增加,当m(EDOT)/m(PS)由0.60增加到1.25时,导电微球的平均粒径由1.76μm增加到1.91μm。     

特殊形态聚合物微球原位负载Ag纳米粒子

以苯乙烯单封端的聚N-异丙基丙烯酰胺(St-PNIPAAm)大分子单体为反应性分散稳定剂,使之与丙烯腈(AN)和少量苯乙烯(St)在醇/水混合介质中进行三元分散共聚反应,制得了以聚苯乙烯(PS)为核,表面接枝PNIPAAm的聚合物微球(PNIPAAm-g-PAN/PS).利用扫描电子显微镜(SEM)观察证实:所得聚合物微球的粒径和表面凸起均一,形态结构规整,其粒径和形态可通过改变聚合反应条件加以控制.以典型配方的聚合物微球为媒介,AgNO3为金属源,乙醇为还原剂,在90 ℃下使Ag纳米粒子原位负载在PNIPAAm-g-PAN/PS聚合物微球表面.利用透射电子显微镜(TEM),紫外光谱(UV)及傅立叶红外光谱(FT-IR)对表面负载Ag纳米粒子的聚合物微球样品进行了表征,结果表明:Ag纳米粒子在特殊形态聚合物微球表面负载均匀,通过改变银离子的用量可将Ag纳米粒子的大小控制在3～32 nm范围内,最小平均粒径约为6 nm.     

沉淀聚合法制备单分散聚(4-乙烯基吡啶-co-二乙烯基苯/三羟甲基丙烷三甲基丙烯酸酯)聚合物微球

以4-乙烯基吡啶(4-VP)为功能单体、二乙烯基苯(DVB)和三羟甲基丙烷三甲基丙烯酸酯(TRIM)为混合交联剂,偶氮二异丁腈(AIBN)为引发剂,乙腈为反应介质,采用沉淀聚合法制备单分散聚合物微球.考察了共聚单体、溶剂、引发剂等聚合条件对聚合物微球粒径、分散性以及产率的影响.并用扫描电镜(SEM)、激光粒度分析仪、热重分析仪和红外光谱对微球进行了表征.结果表明,聚合物微球的表面形貌和产率可通过改变溶剂体积、单体/交联剂摩尔比和引发剂浓度等因素进行控制.降低乙腈溶液体积、增加DVB摩尔比例及交联剂摩尔比、可增加聚合物粒径及粒度分布均匀性,而聚合物产率随溶剂体积和DVB摩尔比增大而减小,随交联剂摩尔比和引发剂浓度的增加而增加.在最优条件下,即DVB和TRIM两者摩尔比4∶1,单体/交联剂摩尔比1∶5,乙腈用量为5.6 m L(单体和交联剂占介质体积的7%),引发剂浓度为2 wt%~6 wt%(占总反应单体的量)时,可获得形貌规则、产率较高的单分散poly(4-VP-co-DVB/TRIM)微球,微球平均粒径约4.02μm,粒径分布指数(U)为1.013.此外,热重分析结果显示,聚合微球于350℃时开始分解,600℃时失重率达84.9%.     

无皂乳液聚合法制备非球形聚苯乙烯粒子研究

采用苯乙烯(St)、二乙烯基苯(DVB)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)为单体,在乙醇和水混合介质中通过无皂乳液聚合法制备了非球形聚苯乙烯(PS)粒子。通过FT-IR、TEM和激光粒度及电位分析仪对粒子的结构、形貌、粒径以及Zeta电位进行了表征。结果表明,所合成PS粒子均含三种单体结构单元,且形貌上均为非球形;随着DVB用量的增加,PS粒子形貌更趋于球形,粒径和单分散系数均逐渐增加;随DMC用量增加,PS粒子粒径随之增加,单分散系数逐渐减小,表面Zeta电位也逐渐增加;KHCO3用量的增加能使PS粒子粒径和单分散系数均增加;随着醇水比的减小,PS粒子粒径逐渐减小,而单分散系数则逐渐增加。     

反应条件对聚合物微球粒径及其分布影响

采用分散聚合的工艺制备出了微米级单分散聚苯乙烯微球，并对分散聚合反应的外部影响因素(反应介质极性、反应体系温度、搅拌速度)进行了研究，研究结果表明：随着反应介质极性的增加，聚苯乙烯微球的粒径战小，粒径分布变化不大；随着反应体系温度的增加，聚苯乙烯微球的粒径增大，粒径分布变化不大，在满足粒径和粒径分布要求的前提下，搅拌速度以低速为宜。     

聚苯乙烯单分散微球粒径可控性探讨

在系统研究分散聚合反应中的原料组成(分散稳定剂、单体、引发剂)和反应条件(反应介质极性、反应体系温度、搅拌速度)对所制备的聚合物微球的粒径大小及粒径分布和聚合反应速率影响的基础上,根据各因素的影响效应,优化设计分散聚合的反应条件,成功地制备出1μm~10μm粒径范围内不同粒径级别的微米级单分散聚合物微球,实现了不同粒径大小及粒径分布的微米级单分散聚合物微球制备的控制设计。     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

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.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.