阴离子和酸度对催化电聚合吡咯膜电化学性质的影响

以循环伏安法和现场可见近红外吸收光谱法，研究了催化电聚合吡咯膜（ＰＰｙ）中嵌入的阴离子的类型和溶液酸度对其在水溶液中电化学性质的影响，实验结果表明在０．３Ｖ静止电位下ＰＰｙ在３８０和８２０ｎｍ处有两个吸收峰，不同于非催化电合成聚吡咯。在－０．９～０．２Ｖ电位范围内，聚合过程中掺入膜中的阴离子能与中性水溶液中的阴离子，如Ｔｉｒｏｎ阴离子，Ｃｌ￣－，ＮＯ，ＣｌＯ和ＳＯ离子等可逆地进行电化学嵌入与脱嵌反应；在酸性水溶液中进行阴离子脱嵌和嵌入过程中，当电位达－０．４Ｖ，会发生新的还原反应，从而引起ＰＰｙ结构和吸收光谱时变化。

电化学催化丙烯酰胺的聚合

为考察氧化还原聚合中的电化学催化效应,在双室电解池中采用铂丝为工作电极进行丙烯酰胺的电解聚合,引发剂为硫酸铈-草酸体系。Ce4+氧化草酸产生自由基,而电解可以使Ce4+再生。对电解和非电解聚合的聚丙烯酰胺产率及分子量进行了对比,结果表明,电解既能大幅提高产率,也能明显提高聚合产物的分子量,即对聚合物链的引发和增长两方面都有促进作用。保证电催化效应的关键因素除适宜的电极电势外,还要有足够大的电极面积与溶液体积之比。

Ti/PbO_2电极上丙烯酰胺/丙烯酸共聚的电催化性能

采用热分解和电沉积的方法制备了Ti/PbO2电极,并在Ti/PbO2电极的电催化作用下,在引发剂硝酸铈铵存在的条件下,成功将丙烯酰胺(AM)和丙烯酸(AA)共同聚合为聚(丙烯酰胺-co-丙烯酸)[P(AM-co-AA)]。利用红外光谱(IR)和循环伏安曲线(CV)讨论了共聚产物及其过程的动力学规律;采用黏度法测定了共聚产物的分子量;考察了在不同单体配比的条件下电流密度、引发剂浓度对共聚产物分子量和共聚反应单体转化率的影响。结果表明:丙烯酰胺和丙烯酸可以在硝酸铈铵Ce(Ⅳ)和电化学催化共同作用下共聚;在单体配比n(AM)∶n(AA)=2.3∶1,电流密度I=0.125A·cm-2,引发剂用量ω[Ce(Ⅳ)]=0.8%的条件下制得相对分子质量为6.5×105的聚(丙烯酰胺-co-丙烯酸),转化率可达到70%。

Electro-polymerization fabrication of PANI@GF electrode and its energy-effective electrocatalytic performance in electro-Fenton process

An energy-effective polyaniline coated graphite felt （PANI@GF） composite cathode for the elec- tro-Fenton （E-Fenton） process was synthesized through an electro-polymerization method. The electrocatalytic activity of the cathode for the 2e- ORR process was investigated and dimethyl phthalate （DMP） was used as a model substrate to evaluate its performance in the E-Fenton process. The as-prepared PANI@GF composite possessed a three-dimensional porous structure, which is favorable for 02 diffusion, while the large amount of N atoms in the conductive polyaniline （PANI） enhanced 2e- ORR reactivity. The DMP degradation of the E-Fenton system using PANI@GF was significantly enhanced owing to the improvement in ORR performance. The apparent kinetic con- stant for DMP degradation was 0.0753 min-1, five times larger than that of GF. The optimal carboni- zation temperature and polymerization time for the preparation of the PANI@GF composite cath- ode was found to be 900 ℃ and 1 h, respectively. Measurement conditions are a crucial factor for proper evaluation of cathode electrocatalytic performance. Accordingly, the 02 flow rate, Fe^2＋ con- centration, and pH for DMP degradation were optimized at 0.4 L/min, 1.0 mmol/L, and 3.0, respec- tively. These results indicate that the present PANI@GF composite cathode is energy-effective and promising for potential use as an E-Fenton system cathode for the removal of organic pollutants in wastewater.

Ethylene Polymerization Using Improved Polyethylene Catalyst

The study concerns the use of MgCl2-supported high-activity Ziegler-Natta catalysts for the polymerization of ethylene.In particular,two types of catalysts were investigated,which were N-catalyst（BRICI）and improved polyethylene catalyst.The effects of catalyst structure on kinetic behavior were examined.The distribution of active centers in these catalysts was investigated by energy dispersive analysis by X-rays（EDAX）,and morphologies of catalyst particles and polymer products were examined by scanning electron microscope（SEM）.Hydrogen response and copolymerization performance were investigated and compared with the two catalysts.The results were correlated with the kinetic behavior of the two catalysts and appropriate models for polymer particle growth were presented.The improved polyethylene catalyst showed higher activity,better hydrogen response and copolymerization performance.

Synthesis of Novel Electron Donors and Their Application to Propylene Polymerization

A series of electron donors,including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE),1,1cyclopentanedimethanol acetic diester (CPDMAD),1,1-biethoxymethyl pentane (BEMP),2,2-diethyl diethylmalonate (DEDEM)and 2,2-diethyl-1,3-propanediol acetic diester (DEPDADE),were synthesized by diethyl malonate (DEM).The purities and structures of the above products were characterized by gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS),respectively.Furthermore,the possible optimal three-dimensional structures of these donors were simulated by means of Gaussian 03 and Chem 3D.Then these electron donors were coordinated with tetrachloro titanium (TiCl 4) and chloride magnesium (MgCl 2)to obtain the catalysts for the polymerization of propylene.The catalytic activities and properties of polypropylene are greatly improved by adding external donor(ED) when CPCADEE or DEPDADE is used as internal donor(ID).However,when BEMP was used as ID,the highest catalytic activity is obtained without adding ED,which can reduce production costs and simplify catalytic synthesis.The experiments indicate that BEMP has the shortest distance of oxygen atoms and the highest electronegativity.

Propylene Polymerization Catalysts with Sulfonyl Amines as Internal Electron Donors

Three sulfonyl aliphatic amines [（R2SO2）2NR1, viz.： compound 1, in which RI=Me, and R2=Ph; compound 2, in which R1=n-Bu, and R2=CF3; and compound 3, in which RI=C8H17, and R2=CF3], have been synthesized and employed as internal electron donors （IED） for the preparation of Ziegler-Natta catalysts for the polymerization of propylene. The contents of Ti, H and C in these catalysts have been determined by elemental analysis and UV-vis spectrophotometry. The effect of the structure and dosage of the electron donor, the A1/Ti ratio and the polymerization temperature on the catalyst performance has been studied. Under optimized conditions, the catalyst with a highest activity yielded polypropylene with high isotacticity in the absence of external electron donors.

Novel MgCl2-supported Catalysts Containing Succinate Donors for Propylene Polymerization

A novel MgCl2-supported Ziegler-Natta catalyst containing diethyl diisopropylsuccinate donor was prepared and propylene polymerizations with the combination of such catalyst and four external donors were investigated in detail. The catalyst was compared with a commercial one with phthalate as internal donor in terms of catalytic activity, hydrogen sensitivity and stereospecificity in propylene polymerization. The molecular weight,molecular weight distribution and microstructure of the produced polypropylenes were compared also. It was found that the novel catalyst containing succinate internal donor showed higher activity and higher stereospecificity than those with phthalate as internal donor. Consequently, polypropylenes obtained by the succinate-based catalyst showed high molecular weight, high melting temperature, high isotactic index and broad molecular weight distribution than those obtained with the commercial catalyst.

Effect of catalyst on formation of poly(methyl methacrylate) brushes by surface initiated atom transfer radical polymerization

Poly （methyl methacrylate） （PMMA） brushes were synthesized from silicon wafers via surface initiated atom transfer radical polymerization （SI-ATRP）. Energy disperse spectroscopy （EDS） and atomic force microscopy （AFM） confirmed that PMMA brushes were successfully prepared on the silicon wafers, and the surface became more hydrophobic according to the contact angle of 69~. It is found that CuCI/1, 1, 4, 7, 10, 10-hexamethyl triethylenetetramine （HMTETA） system is more suitable than CuBr/N, N, N′, N″, N′″-pentamethyl diethylenetriamine （PMDETA） system to control the free radical polymerization of MMA in solution. Nevertheless, better control on the thickness of PMMA brushes was achieved in CuBr/PMDETA than in CuC1/HMTETA due to higher activity and better reversibility of the former system.

Recent development of efficient electrocatalysts derived from porous organic polymers for oxygen reduction reaction

Porous organic polymers(POPs) have recently emerged as promising candidates for catalyzing oxygen reduction reaction(ORR).Compared to conventional Pt-based ORR catalysts, these newly developed porous materials, including both non-precious metal based catalysts and metal-free catalysts, are more sustainable and cost-effective. Their porous structures and large surface areas facilitate mass and electron transport and boost the ORR kinetics. This mini-review will give a brief summary of recent development of POPs as electrocatalysts for the ORR. Some design principles, different POP structures, key factors for their ORR catalytic performance, and outlook of POP materials will be discussed.

Carbon-supported Fe/Co-N electrocatalysts synthesized through heat treatment of Fe/Co-doped polypyrrole-polyaniline composites for oxygen reduction reaction

In this paper,we synthesized cathode catalysts(PANI-PPYR,Fe/PANI-PPYR,Co/PANI-PPYR and Fe-Co/PANI-PPYR)with high performance oxygen reduction by using a simple heat treatment process.These catalysts were fabricated by directly calcining the Fe and/or Co doped polyaniline(PANI)-polypyrrole(PPYR)composites.Their electrocatalytic activity for ORR both in acidic and in alkaline media was investigated by voltammetric techniques.Among the prepared catalysts,Co/PANI-PPYR presents the most positive ORR onset potential of 0.62 V(vs.SCE)in 0.5 mol/L H2SO4 solution or?0.09 V(vs.SCE)in 1 mol/L NaOH solution.In addition,the Co/PANI-PPYR catalyst shows the largest limiting-diffusion current density for ORR,which is 4.3 mA/cm2@0.2 V(vs.SCE)in acidic and 2.3 mA/cm2@?0.3 V(vs.SCE)in alkaline media.In acidic media,a four-electron reaction of ORR on the Co/PANI-PPYR and Fe/PANI-PPYR catalysts is more dominant than a two-electron reaction.In alkaline media,however,a four-electron and a two-electron mechanisms are co-present for the ORR on all the prepared catalysts.Co/PANI-PPYR catalyst also presents good electrocatalytic activity stability for ORR both in acidic and in alkaline media.