Emulsion polymerization of methyl methacrylate under pulsed microwave irradiation

Emulsion polymerization of methyl methacrylate (MMA) under pulsed microwave irradiation (PMI) with higher peak pulse power was studied. The effects of various parameters of PMI on the polymerization were analyzed and compared with that under conventional heating (CH) process. The results were summarized, as compared with that under CH, as follows. The amount of initiator used to reach constant conversion reduced by 50% at the same polymerization time; at the same initiator concentration 0.15 and 0.2 wt.%, the polymerization rate increased by 131% and 163%, respectively. The molecular weight of polymer obtained was 1.1-2.0 times larger than that under CH; at the same irradiation energy, the conversion achieved using a lower pulse power was greater than that using a higher pulse power. There seemed to be a factor of the irradiation energy efficiency; in other words, for the monomer conversion, the irradiation energy of low pulse power had a higher efficiency. The conversion achieved using a 3.5 μs pulse width was almost the same as that using a 1.5 μs pulse width. The results indicated that PMI had a significant non-thermal effect on the emulsion polymerization of MMA so as to effectively enhance the polymerization rate. The glass transition temperature (T_g), the polydispersity index (PDI) and the regularity of the polymer obtained using two processes were similar, indicating that the physical properties and microstructure of the polymer were not modified by the use of microwaves.     

Reactions of substituted furo[3,2-<Emphasis Type="Italic">b</Emphasis>]pyrrole-5-carboxhydrazides and their biological activity

The reactions of substituted furo[3,2-b]pyrrole-5-carboxhydrazides 1 with 5-arylfuran-2-carboxaldehydes 2, 4,5-disubstituted furan-2-carboxaldehydes 3 and thiophene-2-carboxaldehyde 4 has been studied. The advantage of microwave irradiation on some of these reactions was reflected in the reduced reaction time and increased yields. Reactions of 1 with 4-substituted 1,3-oxazol-5(4H)-ones 11 led to diacylhydrazines 13 or to imidazole derivatives 14 depending on the temperature. 1,2,4-Triazole-3-thione 17 was synthesized by two-step reaction of 1 with phenylisothiocyanate and subsequent base-catalyzed cyclization of thiosemicarbazide 16. The effects of hydrazones 5–10 on inhibition of photosynthetic electron transport in spinach chloroplasts and chlorophyll content in the antialgal suspensions of Chlorella vulgaris were investigated.     

微波作用下2,5-二取代-1,3,4-噁二唑的合成

2 ,5 二取代 1 ,3 ,4 二唑可用作药品 ,光敏物质 ,闪烁体 ,激光材料 ,高分子液晶单体等[1- 5] 。一种是以芳香酸与水合肼作为原料用多聚磷酸作为脱水环合剂来合成此类化合物[6 ] ,另一种是由芳香酸转变为芳香酰氯或酯 ,再与水合肼反应得到单酰肼或二酰肼 ,最后用三氯氧磷[7] ,五氧化二磷和五氯化磷[8] ,一氯三甲硅[9] 脱水环合 ;此外 ,用水合肼和尿素合成得到的氨基脲代替水合肼 ,与芳香酸缩合合成二唑[10 ] ,这些方法共同的缺陷是 :环合时间较长 ,少者 4～ 5ｈ ,多则 8ｈ。近年来 ,微波技术在有机合成及其杂环化合物的合成中得到了广…     

氯代膦烯化合物与零价钯的氧化加成反应机理探讨

与氯代烯烃或芳烃相反, 氯代膦烯与零价钯的氧化加成反应可以在温和条件下进行. 提出了可能的反应机理. 起始卤代膦烯的结构决定了反应历程和最终产物的结构.     

白藜芦醇分子的转动惯量和电偶极矩

通过分子轨道理论和杂化轨道理论推断出较稳定的白藜芦醇分子是平面型分子,然后根据白藜芦醇分子结构特点计算了该化合物的一种稳定异构体的转动惯量,用矢量合成法计算了其电偶极矩,为微波辅助白藜芦醇萃取理论研究提供转动惯量和电偶极矩的数据.     

Solid-supported Hantzsch—Biginelli reaction for syntheses of pyrimidine derivatives

The microwave-assisted dry media technology was utilized for the synthesis of some novel derivatives in the Hantzsch—Biginelli reaction. In this eco-friendly approach, the usage of organic solvents and hazardous reagents resulting in corrossion of materials was minimized, giving high yields of products within a short reaction time.     

Micro construction of poly(epsilon-caprolactone)/poly(L-lactic acid) blend film by solution casting under microwave irradiation

The micro construction of poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLLA) blend films fabricated by solution casting under microwave irradiation was investigated by selective enzymatic degradation and scanning electron microscopy (SEM). The results were totally different from the blends obtained by conventional methods. The blend was more homogeneous and the PCL continuous phase more compact as no spherulites and tiny zone separation were observed from the film surface and no PCL network was observed inside the film, and the degradation of a PCL plank by Pseudomonas lipase was significantly retarded. The distributed PLLA micro spheres were enlarged and amorphous. The thermal behavior of the blend by microwave heating revealed that PCL and PLLA underwent a melting process, which induced the variations of the PCL phase and PLLA spheres. The weight loss caused by degradation of the PCL/PLLA blend obtained by conventional methods (B50c) is greater than that of the blend obtained by microwave methods (B50m), which reflects the change in morphology from a loose PCL network (B50c) to a dense PCL plank (B50m).     

微波辐射下无催化剂一锅法合成N-甲基十氢吖啶-1,8-二酮化合物

为了研究从简单易得的原料在无催化剂的条件下一锅法合成N-甲基十氢吖啶-1,8-二酮化合物，我们以各类醛（脂肪醛、芳香醛、二醛）、达咪酮或1,3-环己二酮和甲胺为原料，以乙二醇或水为溶剂，经微波辐射，一步反应得到了一系列N-甲基十氢吖啶-1,8-二酮化合物。反应时间从传统热反应的4-5小时缩短至2-10分钟，产率较高（56-95%），并且不需要使用催化剂。该反应后处理方便，只需要简单洗涤，环境友好，为合成此类化合物提供了一种简便、有效的合成方法。该方法不仅适用于一元脂肪醛、芳香醛，还适用于芳香二醛，因此可以合成含有一个或两个十氢吖啶结构单元的杂环化合物。     

自组装合成纳米复合TiO2-ZnO介孔材料及其光催化性能

以TiCl₄, ZnSO₄•7H₂O为原料, 尿素为沉淀剂, 利用可溶性淀粉大分子链的空间位阻效应和高分子网络的阻隔作用, 以纳米级碳黑为模板, 采用微波加热、均相沉淀法合成出了一系列纳米TiO₂-ZnO复合介孔材料. XRD分析证明反应前驱体为非晶态, 500 ℃以上转变为锐钛矿结构的TiO₂和ZnTiO₃, 当Ti∶Zn＝1(摩尔比)时, 产物全部为ZnTiO₃ (TiO₂•ZnO). TEM形貌观察结合N₂吸附表明, 基本粒子为球形, 粒径15～20 nm. 最可几孔径8～10 nm. EDS分析证明产品中Ti∶Zn的分析测定值与实际的投料值基本一致, 并且掺杂均匀性好. 光吸收及光催化实验发现Zn含量为50%时, 光催化效果最好, 在日光照射90 min后, 此TiO₂-ZnO复合材料对藏蓝染料溶液降解率可达到100%, 其光催化反应符合一级动力学方程.     

微波辐射下三组分“一锅法”合成5-芳基-1,5,6,7,8,9-六氢化-2H-吡唑[5,4-b]并喹啉-6-酮

在微波辐射下以芳醛、1,3-环己二酮或达米酮和氨基吡唑为原料, 用乙二醇作能量转移剂, 三组分“一锅法”快速合成了一系列吡唑[5,4-b]并喹啉类化合物. 该方法速度快(30～90 s), 产率高(88%～98%), 环境友好. 产物结构通过红外光谱、核磁共振谱和元素分析证实, 化合物4e的单晶经X射线衍射分析, 进一步确证了产物结构.