Hydroxyalkylation of barbituric acid. III. Product analysis and reaction pathway

Polyetherols containing a thermally stable pyrimidine ring were obtained upon the reaction of hydroxymethyl derivatives of barbituric acid with an excess of ethylene or propylene oxide. The reaction was monitored by ¹H‐NMR and IR spectroscopy for the systems with variable starting molar ratios of reagents. We found that formaldehyde rearranged from N‐hydroxymethyl and oxymethylene bridges into the end of the polyetherol chain during the reaction. Simultaneously, the O‐hydroxymethyl groups underwent blocking by oxirane. The structures of the polyetherols was deduced on the basis of the course of the reaction and the analytical data. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrooxidation of 4-methylcatechol in the presence of barbituric acid derivatives

Electrooxidation of 4-methylcatechol (1) in the presence of 1,3-dimethylbarbituric acid (2a) and 1,3-diethylthiobarbituric acid (2b) as nucleophiles has been studied in detail by cyclic voltammetry and controlled-potential coulometry. The results indicate that 1 can be oxidized to its related o-benzoquinone (1a) and without conversion to its quinone methide tautomeric form, via an ECEC mechanism pathway, is converted to barbiturate derivatives (5a-b). The electrochemical synthesis of 5a-b have been successfully performed in one-pot in an undivided cell.     

Addition polyimides. I. Kinetics of cure reaction and thermal decomposition of bismaleimides

The thermal polymerization of four structurally different bismaleimide resins, prepared by reacting maleic anhydride with four aromatic diamines, viz., 4,4′-diaminodiphenyl methane, 4,4′-diamino diphenyl ether, 4,4′-diamino diphenyl sulfone, and 3,3′-diamino diphenyl sulfone, was followed by differential scanning calorimetry (DSC). The enthalpy change and the kinetic constants for the polymerization reactions were evaluated from the DSC curves. Thermal stability of the cured polymers was studied by thermogravimetry (TG). The kinetic parameters, viz., activation energy E and preexponential factor A, for the thermal decomposition of the cured bismaleimides were calculated from the TG curves using three nonmechanistic integral equations. The kinetic constants (E and A) follow a trend similar to the thermal stability of the polymers.     

Preparation and characterization of metal-containing bismaleimides from divalent metal salts of p-aminobenzoic acid

A series of novel metal-containing bismaleimides monomers BMI(M) (M = Ca, Sr, Ba, Pb, Co, Ni) were prepared by reacting maleic anhydride with diaminodiphenyl carboxylate to form bismaleamic acid precursors, and subsequently by imidizing them chemically or thermally to form bismaleimides. The samples were characterized by IR, ¹H-NMR, and TG-DTA. The results of thermal analysis show that the BMI(M) have high thermo-oxidiative stability and their temperatures of initial decomposition have a relationship with metals introduced and the imidization methods. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1827–1831, 1997     

高镁炉渣酸解液硅酸自聚-离心脱硅工艺研究

利用酸法提取高炉渣中有价元素的过程中,存在着酸解液硅浓度过高的问题,不利于后续的过滤和金属元素的进一步富集,因此需要进行脱硅操作。针对溶液中硅的脱除问题,基于硅酸自聚原理,提出了硅酸自聚-离心脱硅的实验方法,该方法避免了沉淀法容易引入杂质的问题,适合酸性环境下高浓度硅的脱出。研究了不同实验条件对脱硅率的影响,采用电感耦合等离子体发射光谱（ICP-OES）对脱硅液成分进行分析,并通过X射线衍射（XRD）、扫描电镜-能谱（SEM-EDS）对离心硅渣的晶体结构和微观形貌进行分析,同时采用傅里叶红外（FT-IR）和核磁共振谱（NMR）研究硅酸聚合过程。通过实验发现,脱硅的最适宜工艺条件为：c（H⁺）为3.5 mol/L,反应温度为70 ℃,保温时间为2 h,离心转速为3 500 r/min,离心时间为3 min。在该条件下达到了99.5%的脱硅率。     

Hydroxyalkylation of barbituric acid. I. Hydroxymethyl derivatives of barbituric acid—Precursors of polyetherols with a pyrimidine ring

The reaction of barbituric acid with formaldehyde at variable molar ratios was studied. The structure of the products was elucidated using ¹H‐NMR and IR spectroscopy as well as acidic number and formaldehyde percentage analysis. The products were potential substrates for the synthesis of linear and multifunctional polyetherols with a pyrimidine ring by reaction with oxiranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101:3468–3478, 2006     

扩链双马来酰亚胺的合成与表征

分别合成了一系列酰胺键扩链的双马来酰亚胺和酰亚胺键扩链的双马来酰亚胺，通过ＩＲ，ＨＮＭＲ对其结构进行了表征，并通过ＴＧ－ＤＴＡ对其热性能进行了研究。结果发现它们具有良好的耐热性。     

烯丙基化合物改性双马来酰亚胺

介绍了烯丙基化合物改性双马来酰亚胺树脂(BMI)的反应机理,综述了二烯丙基双酚A、含硼烯丙基化合物、烯丙基醚、烯丙基酚氧树脂等改性BMI体系的研究进展。     

Polycondensation of bismaleimides with aromatic diamines

Summary The polycondensation (Michael addition) of a bismaleimide (BMI, N,N-4,4-[(1-methylethylidene) bis (phenyleneoxyphenylene)] bismaleimide) with an aromatic diamine (DA, 4,4-[1,3 phenylene bis (1-methylethylidene)] bisaniline), in a 1:1 molar ratio, was followed using SEC and FTIR techniques. The polycondensation followed a 2nd-order kinetics with an activation energy, E=51 kJ mol^–1. The mass fraction of dimer varied with conversion following the statistical prediction for an ideal A₂+B₂ polycondensation. At 60% conversion, gelation was observed. This was ascribed to a small advance in the BMI homopolymerization. Thermal degradation took place at T>200 °C. The first step was, possibly, a reversal in the Michael addition reaction as revealed by the decrease in the concentration of CH₂ groups observed in FTIR spectra.This paper is dedicated to Prof. Eloisa B. Mano (IMA, UFRJ, Brazil) for her pioneering work in the development of the polymer field in Latin America.     

双酚A氰酸酯自聚反应机理研究

为了得到性能稳定的氰酸酯,通过傅里叶红外光谱、高效液相色谱、核磁共振等方法研究了双酚A型氰酸酯单体的自聚反应历程,并提出可能的反应方程式以期得到性能稳定的氰酸酯树脂。结果表明,氰酸酯自聚主要通过三聚反应直接生成三聚体、五聚体、七聚体等低聚物,而后体系分子质量逐渐增大形成交联网状结构,并不产生二聚体过渡结构;主催化剂并不改变氰酸酯聚合反应机理,仅是通过降低反应活化能使反应速度加快。     

Synthesis and properties of novel naphthalene-containing bismaleimides

New aromatic bismaleimides containing bis(phenoxy) naphthalene unit, were synthesized. They were prepared by reacting a diamine-containing naphthalene and maleic anhydride by the usual two-step procedure that included ring-opening addition to give bismaleamic acid, followed by cyclodehydration to bismaleimide. The monomers were characterized by infrared (IR), proton nuclear magnetic resonance (H-NMR), elemental analyses (EA), and mass spectra (MS). Their thermal polymerization was investigated by differential scanning calorimetry (DSC). The presence of a naphthalene group in the backbone of the bismaleimide had increased the curing temperature and reduced the reactivity of the maleimide bond. The glass transition temperatures of the polymers were in the range of 291–334°C. Thermogravimetric analyses of the cured resins showed higher thermal stability and char yield for naphthalene-containing bismaleimides than for the corresponding benzene analog. The observed char yield of the bismaleimide resins are in accordance with the calculated C/H ratios. © 1996 John Wiley & Sons, Inc.     

Chain-extended bismaleimides. II. A study of chain-extended bismaleimides as matrix elements in carbon fiber composites

A series of chain-extended bismalemide resins as matrix elements in carbon fibers were cured and characterized in terms of their thermal and thermomechanical properties. The cured resins were stable up to 430°C and EDABMI/MDA has the highest T^g value and the lowest loss modulus value. To understand the compatibility and the degree of adhesion between the resin and the fiber, their surface properties were determined in terms of the surface energy component and single-fiber pull-out tests. The surfaces of the resins were found to have a basic character. The resins containing ether groups have a higher degree of basicity than does the resin containing methylene groups. Similarly, an increasing trend in the interlaminar shear strength (ILSS) and the work of adhesion values were observed with the increasing number of the ether groups in the resin structure. © 1996 John Wiley & Sons, Inc.     

Curing of bismaleimides: 3. Effect of structure on thermal behaviour of bis(amide-maleimide)

This paper describes the synthesis and characterization of six bismaleimide resins containing amide linkages in their backbones. The effect of structure on thermal behaviour was investigated by introducing phosphine oxide, fluorene, ether, methylene, m-phenylene and sulphone groups into the backbone. Thermal characterization of these bismaleimides was achieved using differential scanning calorimetry and thermogravimetric analysis. The presence of an electron withdrawing group in the backbone of the bisimide increased the curing temperature and reduced the reactivity of the maleimide bond. Thermal stability of the cured bismaleimide resins depended on their structure and it was found that the phosphorus and fluorene containing bisimide resins gave high char yields.     

聚合松香与HEMA的酯化及其自聚研究

以聚合松香(PR)和甲基丙烯酸-β-羟乙酯(HEMA)为主要原料,两者酯化反应后得到PRH(酯化物);然后采用自由基聚合法得到PPRH(PRH的自聚物)。研究了单体比例和反应时间对酯化反应的影响,并采用FT-IR(红外光谱)法、GPC(凝胶渗透色谱)法、TGA(热失重分析)法和DSC(差示扫描量热)法等对产物的分子结构、Mr(相对分子质量)及其分布、热稳定性和Tg(玻璃化转变温度)等进行了表征。结果表明:当n(PR)∶n(HEMA)=1∶1.3、反应时间为3 h时,酯化率达到94.1%;不同产物的Tg大小为PR>PPRH>PRH;不同产物的Mr和热稳定性大小均为PR相似文献   

Novel effect of barbituric acid on glass transition temperature of bismaleimide–epoxy resin systems

Barbituric acid (BTA) has a novel influence on glass transition temperature (T_g) of bismaleimide (BMI)–epoxy resin systems. It causes the T_g of a BMI–epoxy resin system to rise significantly. The BTA's influence on T_g was investigated by changing the molar ratio of the reactants. In addition, the influence of benzoperoxide (BPO) on T_g was compared with that of BTA. The reaction selectivity of BTA and diamino-diphenyl sulfone (DDS) toward BMI and epoxy individually in the BMI–epoxy blended systems were studied using the DSC and GPC. By controlling the amount of DDS and BTA, epoxy and BMI could form intercrosslinking networks.     

预处理对石棉尾矿酸浸反应效果的影响

提高石棉尾矿与酸的反应效果是提高利用石棉尾矿制备氢氧化镁和二氧化硅产率的重要途径.本文就石棉尾矿的预处理对石棉尾矿与酸反应效果的影响进行了研究.采用的预处理方法有:将石棉尾矿在700℃下煅烧、超细研磨、浮选提纯等,以预处理后的石棉尾矿与酸反应后的残渣质量作为评价指标.结果表明:预处理没有达到提高石棉尾矿酸浸效果的目的.文中对产生这一结果的原因进行了讨论.     

Hydroxyalkylation of barbituric acid. II. Synthesis of polyetherols with pyrimidine ring

The route of synthesis of new polyetherols with pyrimidine ring from barbituric acid (BA) was presented. The polyetherols were obtained in two steps: synthesis of hydroxymethyl derivative of BA followed by reaction of the latter with neat ethylene or propylene oxides. Physical properties of the products and preliminary application for fabrication of thermal stability polyurethane foams were determined. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

对硝基苯乙酸还原反应的研究

报道了对硝基苯乙酸的四种还原方法,酸性介质中铁粉还原,碱性介质中铁粉还原,Pd/C催化转移氢化及镍催化加氢还原。收率分别为85.3%,92.9%,86.0%和82.9%,产品纯度均达98%以上。对四种方法从原料成本,产品质量,工艺难易程度,环境保护等方面进行了比较。提出了实现工业化生产的初步看法。     

Application of the prins reaction on oleic acid

The probable structure of the various components of oleic acid-formaldehyde adducts is discussed. The adducts are reduced to alcohols by high pressure hydrogenation with copper chromite as a catalyst. The new alcohols are distilled, analyzed and used for the preparation of various esters with carboxylic acids. The esters were evaluated as low temperature lubricant base stocks and low temperature plasticizers.     

5-(2-苯基-1,2,3-三唑-4-次甲基)巴比妥酸及硫代巴比妥酸的合成

巴比妥酸和硫代巴比妥酸及其衍生物是一类具有重要生理活性的含氮杂环化合物,其中5-次甲基(硫代)巴比妥酸是合成药物和杂环化合物的重要中间体.三唑类化合物具有抗菌消炎、抗癌、抗病毒、植物生长调节等活性,被广泛应用于医药、农药方面.