分散共聚法制备特殊形态高分子微球的研究

以聚乙二醇 (PEG)大分子单体为反应性稳定剂 ,在丙烯腈的分散共聚反应中添加少量苯乙烯以形成疏水性核 ,制备得到了亚微米级高分子微球 .透射电子显微镜研究表明 ,该高分子微球具有特异的形态结构 .同时研究了分散共聚体系中各种反应因素对微球形态和直径的影响 ,结果表明 ,苯乙烯单体的添加量、PEG大分子单体的浓度及分子量、混合溶剂的组成对微球直径和形态均有明显的影响 .X 射线光电子能谱 (XPS)研究结果表明 ,微球表面聚集有亲水性PEG链 ,核为疏水的聚 (丙烯腈 苯乙烯 ) ,即形成的特异形态的PEG接枝高分子微球亦为复合型结构     

无规-类接枝共聚物自组装制备交联纳米微球

无规-类接枝共聚物(SFG)由大分子单体-己内酯改性丙烯酸酯(FA)、亲油性单体苯乙烯和甲基丙烯酸缩水甘油酯(GMA)共聚所得，SFG与聚苯乙烯在甲醇溶液中进行自组装，形成核壳结构纳米胶束，进一步对PGMA壳进行化学交联。最终得到具有核壳结构的纳米微球。动态激光光散射和透射电子显微镜表征结果显示SFG自组装形成了窄分布的纳米微球，微球粒径在100～200nm之间。     

热敏性高分子接枝聚苯乙烯微球的制备

通过使聚N－乙烯基异丁酰胺（PNVIBA）大分子单体与苯乙烯在乙醇／水的混合溶剂中进行自由基分散共聚，得到热敏性PNVIBA接枝聚苯乙烯（PNVIBA－g-PSt)高分子微球。用TEM对微球的形态进行了观察，同时考察了起始PNVIBA大分子单体浓度、苯乙烯浓度、引发剂浓度、聚合温度和混合溶剂中水对微球直径的影响。发现在较宽的聚合反应条件下，得到的接枝高分子颗粒均保持球形并具有单分散性，微球的数均直径（D）与反应条件的关系遵循：D＝K[PNVIBA]^-0.39[St]^0.80[I]^-0.14;微球直径随聚合温度的升高和混合溶剂中水含量增加而降低；颗粒形态可以通过改变聚合反应条件或添加第二小分子单体加以控制。     

PVA-g-PS复合微球的制备与粒径控制研究

由链转移自由基聚合与端基置换反应法,合成了苯乙稀基单封端的聚醋酸乙烯酯(PVAc)大分子单体,使其与苯乙烯在乙醇/水的混合介质中进行自由基分散共聚,得到了表面以PVAc为接枝链的聚苯乙烯(PVAc-g-PSt)微球。将所得微球在碱性条件下醇解,形成了以亲水性聚乙烯醇(PVA)为壳、聚苯乙烯为核的复合微球(PVAc-g-PSt)。用核磁共振对聚合物的结构进行表征,定出了PVAc末端双键的含量;并用激光光散射、扫描电子显微镜对微球的粒径与形态进行了表征。研究结果表明,在共聚反应体系中大分子单体的分子量与浓度、苯乙烯浓度、引发剂浓度及溶剂的组成对微球的形态和粒径大小有明显影响。     

醇/水介质对PEG大分子单体与BMA分散共聚反应的影响

通过端基反应法合成了苯乙烯单封端的聚乙二醇(St- PEG)大分子单体,使其与甲基丙烯酸丁酯(BMA)在乙醇 水混合介质中进行分散共聚,得到了聚乙二醇接枝的聚甲基丙烯酸丁酯(PBMA- g -PEG)高分子微球.PBMA- g -PEG共聚物的亲溶剂 疏溶剂平衡将影响微球的形成,反应结束时,体系随BMA浓度和介质中水含量的变化呈现出4种不同的状态,透明清液、乳液、伴有沉淀或凝胶的乳液和凝胶.用透射电子显微镜(TEM)和激光光散射(LLS)对乳液体系的粒径及其形态进行了表征,表明所得接枝高分子微球形态规整具有较好的单分散性.通过控制介质中水的含量和BMA的浓度可得粒径在4 0～5 0 0nm范围的PBMA -g -PEG微球.     

负载型纳米Ag颗粒的制备及其催化性能研究

利用聚4-乙烯基吡啶(P4VP)大分子单体与苯乙烯(St)进行分散聚合一步法制备得到粒径均一的聚4-乙烯基吡啶(P4VP)-g-聚苯乙烯(PS)共聚物微球(P4VP-g-PS)。研究发现通过调控反应介质中混合溶剂的极性、P4VP大分子单体用量可控制微球粒径。将其作为Ag载体,使Ag+原位还原成Ag纳米颗粒,在催化亚甲基蓝(MB)的实验中使MB的降解量达到96. 7%。     

PAm-g-PMAA亲水性聚合物微球的合成

利用链转移自由基聚合和端基置换反应法 ,合成了苯乙烯基单封端的聚甲基丙烯酸叔丁酯 (PBMA)大分子单体 .在N ,N′ 亚甲基二丙烯酰胺 (Bis A)存在的条件下 ,使PBMA大分子单体与亲水性单体丙烯酰胺(Am)在乙醇 水的混合介质中进行分散共聚反应 ,得到了表面为PBMA接枝的聚丙烯酰胺 (PAm g PBMA)聚合物微球 .将所得PAm g PBMA微球在酸性条件下水解 ,得到了整体亲水的聚甲基丙烯酸接枝的聚丙烯酰胺(PAm g PMAA)聚合物微球 .用激光光散射、透射电子显微镜和X射线光电子能谱仪等对聚合物微球的直径、形态及表面组成进行了表征 .研究结果表明 ,在共聚反应中PBMA大分子单体的分子量与浓度、Bis A浓度和介质的组成对微球的形成与颗粒直径的大小有明显影响 ;所形成的聚合物颗粒是以PBMA为壳、以交联PAm为核的核壳结构微球 .     

热敏性聚(N-乙烯基异丁酰胺)接枝高分子微球的合成

用自由基聚合和端基反应法合成了大分子单体聚 (N 乙烯基异丁酰胺 ) (PNVIBA) ,将其与苯乙烯在乙醇 水的混合溶剂中进行分散共聚 ,得到了PNVIBA接枝聚苯乙烯 (PNVIBA g PSt)高分子微球 .用GPC、激光光散射和电子显微镜等对聚合物的分子量和微球直径及形态进行了表征 .研究结果表明 ,大分子单体PNVIBA和PNVIBA g PSt高分子微球具有明显的热敏性 ,并且发现PNVIBA g PSt微球直径和形态可通过改变反应条件加以控制 ,得到了一种新形态的亚微米级高分子微球     

特殊形态接枝高分子颗粒的合成

表面接枝高分子微球具有分子结构的可设计性 ,分散稳定性好 ,被用于高效催化剂的载体、药物释放控制和疾病治疗等生物医学领域 ,因而引起了许多高分子材料和生物医学工作者的极大兴趣[1～ 3] .我们用链转移自由基聚合法合成了一端为苯乙烯基封端的聚乙二醇 ( PEG)和聚 ( N -异丙基丙烯酰胺 )等亲水性大分子单体 .在与疏水性单体如苯乙烯等的二元分散共聚反应中 ,利用接枝共聚物在溶液中的自组装 ,制备了粒径分布均一 ,颗粒表面形态光滑 ,同时表面具有功能性高分子链的微球 [4～ 8] .传统的合成高分子微球的研究主要是以苯乙烯或甲基丙烯酸…     

原子转移自由基聚合合成聚乙烯胺大分子单体及其共聚反应研究

以水为反应介质, 采用原子转移自由基聚合(ATRP), 在70 ℃下合成了末端为溴原子的聚丙烯酰胺预聚体(PAM-Br). 利用水相凝胶渗透色谱(GPC)对PAM-Br的相对分子质量和分子量分布进行了表征, 结果表明: 单体浓度、单体与引发剂物质的量之比和反应时间对PAM-Br的分子量及其分布有较大的影响, 在较低AM单体与引发剂物质的量比条件下, 其聚合过程符合ATRP的基本规律. 进而使PAM-Br预聚体末端的溴原子与甲基丙烯酸(MAA)进行亲核取代反应, 得到了末端带有不饱和双键的大分子单体(MAA-PAM). 并利用霍夫曼降解制备出了部分胺解的聚乙烯胺(MAA-PVAm)大分子单体, 其结构由傅里叶变换红外(FTIR)和核磁共振仪(NMR)的表征得到了确定. 以得到的大分子单体为反应性分散稳定剂, 与苯乙烯在乙醇/水的混合介质中进行分散共聚反应, 制得了聚苯乙烯接枝MAA-PVAm (PS-g-PVAm)复合微球, 由扫描电子显微镜(SEM)观察发现: 微球保持规整的球形结构, 粒径分布均一, 有较好的单分散性.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

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.