Polymerization products of p-benzoquinone as thermal stabilizers for rigid poly(vinyl chloride): Part I—Preparation of the stabilizer

The solid phase cationic polymerization of p-benzoquinone using tin (II) chloride as catalyst has been investigated by isolation and identification of the reaction products. The polymerization reaction leads to formation of polymeric chains of hydroquinone nuclei linked together by SnOSn bonds and free from combined chlorine. The tin content of the polymer is increased by increasing the molar ratio of the catalyst and ranges from 4·7 to 55·6% tin. It is probable that the tin atoms are involved in the reaction products as a result of the interaction between polymeric chains having terminal catalyst residues. The resulting polymeric products are characterized by high thermal stability with a decomposition temperature in the region of 400°C. A mechanism which can account for the polymerization products has been developed. In view of the expected high potency of these products, together with their high thermal stability, they will be investigated as radical scavengers in the stabilization of polymeric material against radical degradation processes.     

Cross-coupling reaction of alpha-chloroketones and organotin enolates catalyzed by zinc halides for synthesis of gamma-diketones

The reaction of tin enolates 1 with alpha-chloro- or bromoketones 2 gave gamma-diketones (1,4-diketones) 3 catalyzed by zinc halides. In contrast to the exclusive formation of 1,4-diketones 3 under catalytic conditions, uncatalyzed reaction of 1 with 2 gave aldol-type products 4 through carbonyl attack. NMR study indicates that the catalyzed reaction includes precondensation between tin enolates and alpha-haloketones providing an aldol-type species and their rearrangement of the oxoalkyl group with leaving halogen to produce 1,4-diketones. The catalyst, zinc halides, plays an important role in each step. The carbonyl attack for precondensation is accelerated by the catalyst as Lewis acid and the intermediate zincate promotes the rearrangement by releasing oxygen and bonding with halogen. Various types of tin enolates and alpha-chloro- and bromoketones were applied to the zinc-catalyzed cross-coupling. On the other hand, the allylic halides, which have no carbonyl moiety, were inert to the zinc-catalyzed coupling with tin enolates. The copper halides showed high catalytic activity for the coupling between tin enolates 1 and organic halides 7 to give gamma,delta-unsaturated ketones 8 and/or 9. The reaction with even chlorides proceeded effectively by the catalytic system.     

Quantification of Zinc Atoms in a Surface Alloy on Copper in an Industrial‐Type Methanol Synthesis Catalyst

Methanol has recently attracted renewed interest because of its potential importance as a solar fuel. 1 Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al₂O₃ catalyst. The identity of the active site and, in particular, the role of ZnO as a promoter for this type of catalyst is still under intense debate. 2 Structural changes that are strongly dependent on the pretreatment method have now been observed for an industrial‐type methanol synthesis catalyst. A combination of chemisorption, reaction, and spectroscopic techniques provides a consistent picture of surface alloying between copper and zinc. This analysis enables a reinterpretation of the methods that have been used for the determination of the Cu surface area and provides an opportunity to independently quantify the specific Cu and Zn areas. This method may also be applied to other systems where metal–support interactions are important, and this work generally addresses the role of the carrier and the nature of the interactions between carrier and metal in heterogeneous catalysts.     

ICP-AES法测定焊锡中铜铁铝锌

本文以ICP-AES法测定焊锡中铜、铁、铝、锌。提出了不用分离锡、铅,直接测定前三个元素的可行性;及分离锡、铅后,四元素同时测定的可行性;并对测定条件、测定方法和分离锡铅的步骤进行了研究。方法比较简便,能满足焊锡样品测定的要求。     

Silicon‐ and Tin‐Based Cuprates: Now Catalytic in Copper!

Silicon‐ and tin‐containing molecules are versatile building blocks in organic synthesis. A stalwart method for their preparation relies on the stoichiometric use of silicon‐ and tin‐based cuprates, although a few copper(I)‐catalyzed or even copper‐free protocols have been known for decades. In this Concept, we describe our efforts towards copper(I)‐catalyzed carbon? silicon and also carbon? tin bond formations using soft bis(triorganosilyl) and bis(triorganostannyl) zinc reagents as powerful sources of nucleophilic silicon and tin. Conjugate addition, allylic substitution, and carbon? carbon multiple bond functionalization is now catalytic in copper!     

Modulation of the Aerobic Oxidative Polymerization in Phenylazomethine Dendrimers Assembling Copper Complexes

The aerobic oxidative polymerization of phenol derivatives can provide poly(phenylene oxide)s, which are known as engineering plastics. This oxidation can be carried out with atmospheric oxygen molecules as the oxidizing reagent in the presence of copper complexes as the catalyst; however, stoichiometric or excess amounts of bases are also generally required. By using a phenylazomethine dendrimer complexed with several equivalent amounts of copper chloride, the additive (base)‐free polymerization of 2,6‐difluorophenol was successful with a very small amount of the catalyst (0.7 mol % of copper for the monomer) because the dendrimer was composed of many Schiff base units, affording a base and catalyst (copper complex) condensed reaction field. The resulting polymer was nearly linear and the molecular weight was very high. When the equimolar amount of the copper complex in one dendrimer molecule was increased, the polymer obtained under this reaction condition was rather branched, resulting in a higher glass transition temperature.     

Chemical Recycling of End-of-Life Poly(lactide) via Zinc-Catalyzed Depolymerization and Polymerization

The chemical recycling of poly(lactide) was investigated based on depolymerization and polymerization processes. Using methanol as depolymerization reagent and zinc salts as catalyst, poly(lactide) was depolymerized to methyl lactate applying microwave heating. An excellent performance was observed for zinc(II) acetate with turnover frequencies of up to 45000 h⁻¹. In a second step the monomer methyl lactate was converted to (pre)poly(lactide) in the presence of catalytic amounts of zinc salts. Here zinc(II) triflate revealed excellent performance for the polymerization process (yield: 91 %, M_n ∼8970 g/mol). Moreover, the (pre)poly(lactide) was depolymerized to lactide, the industrial relevant molecule for accessing high molecular weight poly(lactide), using zinc(II) acetate as catalyst.     

直读光谱法测定析出锌中铅、铜、铁、镉、锡、铝的含量

研究了湿法冶炼产出的析出锌,经过冲床冲压脱模、马弗炉高温熔化、模具浇铸成型、车床切削等过程,于直读光谱仪上测定析出锌中铅、铜、铁、镉、锡、铝含量的方法.通过实验确认了仪器的工作条件、熔样器皿、熔样温度、析出锌取样位置,并对熔样铸锭后铅、铜、铁、镉、锡、铝的偏析情况进行了分析,铅最大偏差达到30％,经玻璃棒搅动后保温,铅...     

Recyclable Cu nanoparticle catalyzed azide-alkyne click polymerization

The Cu(I)-catalyzed alkyne-azide cycloaddition(CuAAC) has been developed into a powerful polymerization reaction for the synthesis of new polytriazoles with versatile properties. However, research on recyclable and reusable copper catalyst for click polymerization to meet the requirement of green chemistry was rarely reported. Copper nanoparticles were reported to be capable catalysts for CuAAC. Replacing conventional copper catalyst with copper nanoparticles may realize the recycle and reuse of the copper catalyst in click polymerization. In this paper, copper nanoparticles were prepared and used as an effective catalyst for click polymerization, and soluble polytriazoles with high molecular weights were obtained in excellent yields under optimized reaction conditions. Importantly, the copper nanoparticles can be recycled and reused for up to 11 times for the click polymerization. Moreover, introducing aggregation-induced emission(AIE)-active moiety of tetraphenylethylene into the monomers makes the resultant polymers retain the AIE feature. This work not only provides an efficient recyclable catalytic system for the azide-alkyne click polymerization, but also might inspire polymer chemists to use recyclable copper species to catalyze other polymerizations.     

Comparative study of transition metal-doped calcined Malaysian dolomite catalysts for WCO deoxygenation reaction

In the present work, nickel (Ni), zinc (Zn), copper (Cu), cobalt (Co) and iron (Fe) are tested as catalyst dopants on Malaysian dolomite calcined at T = 900 °C (CMD900). The physicochemical properties of all synthesised catalyst are investigated by X-ray diffraction, Brunauer–Emmett–Teller surface area, temperature-programmed desorption of carbon dioxide and scanning emission microscopy. The synthesised catalysts are tested on the basis of the deoxygenation (DO) reaction of waste cooking oil to produce liquid fuels under N₂ atmosphere. The chemical composition of the liquid product is identified by gas chromatography–mass spectroscopy. The overall study suggests that Ni/CMD900 catalyst exhibits the highest performance with over 67.0% conversion and high selectivity (80.2%) with a high proportion of saturated linear hydrocarbons that corresponds to green diesel. Result indicates that Ni/CMD900 is a highly potential DO catalyst with 19.8% oxygenated compound, which is favourable for decarboxylation and/or decarboxylation predominates.     

Polymerization of alkylene oxides by dialkylzinc–lewis base systems

Dialkylzinc–Lewis base systems are found to be active catalysts for the polymerization of alkylene oxides. The diethylzinc–dimethyl sulfoxide system is especially effective in the preparation of high polymers of ethylene oxide and propylene oxide. Diethylzine does not react with dimethyl sulfoxide, but there is strong association between the compounds. The proton magnetic resonance spectrum of a poly(ethylene oxide) prepared by the catalyst system suggests that the n-butoxyl group is attached to the end of the polymer chain. Polymerization of ethylene oxide seems to be initiated by the ethyl–zinc bond. The active species of the system seems to be diethylzinc coordinated with dimethyl sulfoxide. The efficiency of the catalyst system for the formation of high molecular weight polymer is 10^?1?10^?2. The other part of the catalyst is responsible for the formation of low polymers.     

Continuous Controlled Radical Polymerization of Methyl Acrylate in a Copper Tubular Reactor

The use of copper tubing as both the reactor and as a catalyst source is demonstrated for continuous controlled radical polymerization of methyl acrylate at ambient temperature and at low solvent content of 30%. The high surface area provided by the copper walls mediates the reaction via the single electron transfer–living radical polymerization (SET‐LRP) mechanism. The polymerizations proceeded quickly, reaching 67% conversion at a residence time of 16 min. Ligand concentration could also be reduced without a sharp drop in polymerization rate, demonstrating the potential for decreased raw material and post‐process purification costs. Chain extension experiments conducted using synthesized polymer showed high livingness. The combination of living polymer produced at high polymerization rates at ambient temperature and low volatile organic solvent content demonstrate the potential of a copper reactor for scale up of SET‐LRP.

     

海藻酸酮膜表面的配位结构及催化MMA聚合的性能

将海藻酸钠(SA)与CuCl2.2H2反应得到一种配位聚合物海藻酸酮(Cu-An)。以ESR、电导率、IR和SPS方法对此配位聚合物进行表征,确定了组成与结构：同时研究了甲基丙烯酸甲酯(MMA)在该配位聚合物膜、HSO3^-和水体系催化引发作用下的聚合反应历程。结果表明,配位聚合物的中心离子Cu^2^+与两个海藻酸(An)链节单元上的两个羧羟基氧原子和两个离解氢原子的羧羟基氧原子以共价型配位,配位数为4.MMA在上述的催化引发体系中是按照自由基加聚反应历程进行聚合的,PMMA呈无规结构。Cu-An在催化引发体系中起着催化剂的配位催化作用。     

Copper-promoted enantioselective Reformatsky-type reaction with ketones

Controlled living polymerization of a broad range of monomers is a radical process known as ATRP (atom transfer radical polymerization) and is mediated by a variety of metals. A complex of copper has been found to be the most efficient catalyst, with a copper(I)/copper(II) catalytic cycle. The radical, enantioselective catalytic Reformatsky reaction mediated by Me₂Zn can be efficiently promoted by copper(I) complexes avoiding the use of other promoters such as air and oxidant, giving more reproducible and affordable conditions. The CuCN-mediated enantioselective addition of ethyliodoacetate to functionalized ketones is described in this paper.     

Rapid complexometric analysis of brass with CTDA

A method for the analysis of brass is presented. The lead, iron, nickel and zinc components are determined titrimetrically with the complexing agent CDTA (disodium dihydrogen 1,2-diaminocyclohexane N,N,N',N'-tetraacetate [also known as HexaVer]). The copper and the tin are weighed as metallic copper and as stannic oxide. The method is more rapid and convenient, especially for routine analysis, than the all-gravimetric procedure and it provides at least equal accuracy and precision.     

低毒锌类催化剂制备聚乳酸的研究

采用低毒锌类催化剂制备了一系列具有高分子量、不同光学纯度及热力学性质的聚乳酸材料. 以金属锌作催化剂制备丙交酯, 研究了不同裂解温度对产物光学纯度的影响. 随后在低毒催化剂乳酸锌的作用下使丙交酯开环聚合, 进一步研究了单体的光学纯度对聚乳酸立体规整性的影响, 以及聚合过程中的结晶对聚合物分子量和热力学行为的影响. 并用旋光仪、核磁共振氢谱(1H NMR)、凝胶渗透色谱(GPC)、差示扫描量热分析(DSC)等方法对产物进行表征. 结果表明, 合适的裂解温度有利于合成高光学纯度的丙交酯; 在低毒乳酸锌的催化作用下, 高光学纯度的单体以及聚合过程中的结晶都有利于制备高分子量聚乳酸.     

Polymerization of olefin oxides with zinc n-butyl xanthate and zinc dimethyldithiocarbamate catalysts: Mechanism of initiation

Xanthates and dithiocarbamates of metals have been reported to be effective as catalysts for the polymerization of olefin oxides. To investigate the mechanism of initiation, the bulk polymerization at 50°C of 1,2-butene oxide with zinc n-butyl xanthate (ZBX) at a monomer: ZBX molar ratio of 584: 1 was studied by ultraviolet and infrared spectroscopy. There is a rapid conversion of the sulfur–zinc bond in the metal xanthate to a structure containing sulfur–carbon and oxygen–zinc bonds, the latter acting as the site of the propagation step during polymerization. The xanthate ester moiety is subsequently converted to the oxygenated analogs, namely, O,O-dialkylthiocarbonate and dialkyl carbonate. These changes are independent of the propagation step. The changes observed in the polymerization of butene oxide with zinc dimethyldithiocarbamate are similar, but much slower than in the case of ZBX. The presence of the carbonate ester moiety was also shown in the benzene-insoluble, catalytically active fraction isolated from seeded catalyst, i.e., from the reaction product of propylene oxide and ZBX at a molar ratio of 8:1 or lower. This fraction also contained ionic sulfur.     

Study of Different Catalysts and Initiators in Bulk Copolymerization of d,l-Lactide and Glycolide

Poly(d,l-lactide-co-glycolide), PLGA, is a biodegradable polyester with many medical applications. In this article, several catalysts are studied as potential substitutes of the conventional catalyst, tin (II) 2-ethylhexanoate (known as tin octoate, SnOct₂). Namely, different metal carboxylates have been examined, in order to study the influence of the metal counterion. Among them, most promising results have been obtained when using zinc (II) 2-ethylhexanoate (ZnOct₂) followed by potassium (I) 2-ethylhexanoate. Furthermore, in the case of ZnOct₂, the use of alcohols as initiators was examined in order to improve reaction rate and to study their effect on molecular weight distribution, polymer microstructure, and side reactions, such as transesterification reaction.     

Synthesis and ring‐opening polymerization of new monoalkyl‐substituted lactides

New monoalkyl‐substituted lactides were synthesized by reaction of α‐hydroxy acids with 2‐bromopropionyl bromide, and polymerized with various catalysts in the presence of benzyl alcohol by ring‐opening polymerization (ROP). The classic tin(II) 2‐ethylhexanoate (Sn(Oct)₂) catalyst was leading to polymers with narrow distribution and predictable molecular weights, in polymerizations in bulk or toluene at 100 °C. The polymerization rate was corresponding to the steric hindrance of the alkyl substituents, such as butyl, hexyl, benzyl, isopropyl, and dimethyl groups. A yield of 83% was obtained with the hexyl‐substituted lactide after 1 h of polymerization. Excellent conversions (97%) could be achieved by using the alternative catalyst 4‐(dimethylamino)pyridine (DMAP). This latter organic catalyst was most efficient in polymerizing the more steric‐hindered lactides with good molecular weight and polydispersity control, in comparison to the tin(II) 2‐ethylhexanoate and tin(II) trifluoromethane sulfonate [Sn(OTf)₂] catalysts. The efficiency of the DMAP catalyst and the variability of the monomer synthesis route for new alkyl‐substituted lactides allow to prepare and to envision a wide range of new functionalized polylactides for the elaboration of tailored materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4379–4391, 2004     

Atom transfer radical polymerization of ionic liquid 2‐(1‐butylimidazolium‐3‐yl)ethyl methacrylate tetrafluoroborate

Polymeric forms of ionic liquids may have many potential applications because of their high thermal stability and ionic nature. They are generally synthesized by conventional free‐radical polymerization. Here we report a living/controlled free‐radical polymerization of an ionic liquid monomer, 2‐(1‐butylimidazolium‐3‐yl)ethyl methacrylate tetrafluoroborate (BIMT), via atom transfer radical polymerization. Copper bromide/bromide based initiator systems polymerized BIMT very quickly with little control because of fast activation but slow deactivation. With copper chloride as the catalyst and trichloroacetate, CCl₄, or ethyl α‐chlorophenylacetate as the initiator, BIMT was polymerized at 60 °C in acetonitrile with first‐order kinetics with respect to the monomer concentration. The molecular weight was linearly dependent on the conversion. The monomer concentration strongly affected the polymerization: a low monomer concentration caused the polymerization to be incomplete, probably because of catalyst disproportionation in polar solvents. The addition of a small amount of pyridine suppressed such disproportionation, but a further increase in the amount of pyridine greatly slowed the polymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5794–5801, 2004