光催化氧化降解聚乙二醇的机理研究

以纳米TiO2为光催化剂,对聚乙二醇水溶液进行光催化降解实验.气相色谱、热重、红外、核磁共振等测定结果表明降解过程有低分子量聚乙二醇和甲酸酯及其他低分子量酯等中间产物生成,最终矿化为CO2和H2O.     

聚乙二醇对纳米二氧化钛性质和应用的影响

二氧化钛纳米晶光催化材料是近年来发展起来的新型环境友好材料,国内外研究者在利用二氧化钛纳米晶光催化降解苯酚、氯酚、甲醛等污染物方面做了大量的研究工作。研究表明TiO2的3种晶型,锐钛矿型、金红石型和板钛矿型中,有光催化作用的主要是锐钛型和金红石型,其晶型和晶粒大小     

纳米SnO2的制备条件及其光催化活性

纳米粒子;光催化降解;纳米SnO2的制备条件及其光催化活性     

负载型纳米TiO2光催化降解活性艳红X-3B染料

光催化氧化;负载型纳米光催化剂;负载型纳米TiO2光催化降解活性艳红X-3B染料     

微波加热反应制备纳米TiO2混晶及其光催化性能

微波加热反应制备纳米TiO2混晶及其光催化性能;纳米二氧化钛;混晶;微波加热;光催化性能     

不规则形ZnO纳米棒的制备及其光催化性能研究

本文采用溶剂热法,以Zn(NO3)2,NaAc为原料,聚乙二醇-10000为表面活性剂,制备了不规则形的ZnO纳米棒。并用X-射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、荧光光谱、紫外-可见分光光度计对其进行了表征。考察了硝酸锌用量、聚乙二醇-10000用量、反应时间和反应温度等对氧化锌粒子形貌和大小的影响,初步讨论了氧化锌纳米棒的可能形成机理。以ZnO纳米棒作为光催化剂,考察了其光催化降解龙胆紫的性能。研究了催化剂用量、龙胆紫的初始浓度对光催化降解率的影响。     

掺铁纳米TiO2的制备及其光催化性能

掺铁纳米TiO2的制备及其光催化性能;掺铁纳米TiO2;微波合成;光催化降解;维生素B12     

酞菁钴/SnO2纳米复合材料的原位合成及可见光光催化

酞菁钴/SnO2纳米复合材料的原位合成及可见光光催化;SnO2;酞菁钴;纳米复合材料;原位合成;光催化     

金属掺杂氧化锌的光催化研究进展

纳米ZnO作为降解污染物的光催化剂，不仅具有成本低、高效、无毒等特点，还能吸收大部分太阳光，是一种性能优异的功能材料。尽管国内外研究人员已经在纳米ZnO光催化材料方面做了大量的工作，但它仍然是研究的热点，因为纳米ZnO除了不同形貌引起的光催化活性变化之外，还可以通过掺杂单金属、多金属和其他金属氧化物，来提高自身光催化活性，并在染料降解、抗菌等方面展示出优异的性能。基于上述背景，总结近年来金属掺杂纳米ZnO对光催化性能的研究进展，为纳米ZnO在光催化方面的研究提供参考。     

聚乙二醇甲醚-聚(D,L-乳酸)嵌段共聚物纳米胶束的制备

聚乙二醇甲醚-聚(D;L-乳酸)嵌段共聚物纳米胶束的制备;聚乙二醇单甲醚;两亲性二嵌段共聚物;纳米沉淀技术     

聚己内酯－聚乙二醇嵌段共聚物Ⅱ．组成、结晶性同降解性间关系

采用ＤＳＣ法测定了新嵌段共聚物聚己内酯（ＰＣＬ）－聚乙二醇（ＰＥＧ）嵌段共聚物（ＰＣＥ）的结晶性，研究了共聚物的结晶性同组成及降解性的关系．结果表明随着共聚物中ＰＥＧ组分的含量和分子量增加，共聚物的结晶性下降，亲水性提高，降解速度加快．     

聚己内酯－聚乙二醇嵌段共聚物Ⅱ．组成、结晶性同降解性间关系

采用ＤＣＳ法测定了新嵌段共聚物聚己内酯－聚乙二醇嵌段共聚物的结晶性，研究了共聚物的结晶性同组成及降解性的关系。结果表明随着共聚物中ＰＥＧ组分的含量和分子量增加，共聚物的结晶性下降，亲水性提高，降解速度加快。     

Photocatalytic activity of TiO2 prepared by adding polyethyleneglycol

TiO₂ was produced by the sol-gel method with the addition of polyethyleneglycol (PEG) to study the effects of the molecular weight and the addition percentage of PEG. Bisphenol A (BPA) degradation rate constants were highest as 3.07, 4.02 and 4.23 h⁻¹ at PEG addition percentages of 10%, 5% and 0.5%. After 12 h reaction, the total organic carbon (TOC) reductions in UV/TiO₂, UV/TiO₂/PEG(200, 10%), UV/TiO₂/PEG(600, 5%) and UV/TiO₂/PEG(3500, 0.5%) systems were 44%, 24%, 19% and 23%, in order. The results demonstrated that adding an appropriate percentage of PEG to the TiO₂ preparation processes increased the BPA degradation and TOC reduction.     

Catalytic Oxidative Deformylation of Polyethylene Glycols with the Participation of Molecular Oxygen

The kinetics of oxidation of diethylene glycol, triethylene glycol, and polyethylene glycols (PEGs) with molecular weights ranging from 400 to 2000 in the presence of Cu(II) ions and bases was studied. It was found that ethylene glycols can be oxidized by molecular oxygen in anhydrous media in a temperature range of 30–60°C at anomalouosly high rates which are higher than the rates of chain-radical PEG autoxidation by several orders of magnitude. Only terminal hydroxyl groups were subjected to oxidation. The reaction occurs with the cleavage of a C–C bond and results in the formation of formic acid and a PEG with the number of –(CH₂CH₂O)– groups lower than that in the parent compound by unity. The rate and selectivity of PEG oxidation were found to strongly depend on the molecular weight of the polymer; from diethylene glycol to PEG 2000, the specific rate of oxidation increased by a factor of 60 in terms of terminal hydroxyl groups. An oxidation mechanism was suggested, which involves the formation of ternary complexes [Cu²⁺···A^–···O₂], which undergo further degradation by a many-electron concerted mechanism to form formic acid and, probably, an unstable hemiacetal {RO–CH₂OH}. The rapid oxidative degradation of the latter leads to the formation of PEG with a lower molecular weight.     

SalenAl(O~iPr)催化CO_2与氧化环己烯共聚及影响因素研究

以SalenAl(OiPr)为催化剂,分别加入各种路易斯碱作为共催化剂催化二氧化碳与氧化环己烯共聚,发现共聚催化效率与共催化剂的供电子能力有关.分别研究催化剂浓度、共催化剂的用量、反应时间、反应温度、CO2压力等各种因素对该共聚反应的影响,发现SalenAl(OiPr)浓度为2 g/L时,以等摩尔量的二甲氨基吡啶(DMAP)作为共催化剂,在4 MPa的CO2和80℃下反应32 h,可得到碳酸酯键含量>99%的共聚产物,其催化效率高达495 g/g,13C-NMR检测表明共聚物为无规立构聚合物,GPC测得分子量Mn为55900,分子量分布比较窄(PDI=1.32).DSC得到共聚物的玻璃化转变温度为136℃,热重分析(TGA)可以看出共聚物在350℃可完全分解,具有优良的热分解性.     

Production and characterization of poly(3-hydroxybutyrateco-3-hydroxyhexanoate)-poly(ethylene glycol) hybird copolymer with adjustable molecular weight

A novel natural-synthetic hybrid block copolymer was synthesized by Aeromonas hydrophila 4AK4 in poly(ethylene glycol)(PEG,M_n=200) modified fermentation.This hybrid biomaterial consists of the natural hydrophobic polymer poly(3-hydroxybutyrat-co-3-hydroxyhexanoate)(PHBHHx) end-capped with hydrophilic PEG,which has the increased flexibility as well as the improved thermal stability.Addition of diethylene glycol(DEG) and ethylene glycol could not result in the accumulation of hybrid block copolymer.DEG and ethylene glycol,together with PEG-200,could cause a reduction of molar mass of PHBHHx,resulting in a series of low molecular weight polymer and the reduction of the polymer yield as well as the cellular productivity.In vitro degradation of PHBHHx and PHBHHx-PEG with different molecular weight showed that the decrease of molecular weight accelerated the degradation of copolymers,but PEG modification has little effect on its degradation rate.The results in this study provided a convenient and direct method to produce a series of PHBHHx and PHBHHx-PEG materials with adjustable molecular weight and broad molecular weight distribution which will be very useful for the biomedical applications.     

可降解PET/PEG共聚物的合成

利用聚合物法通过熔融缩聚直接合成了可降解的PET／PEG共聚物，通过红外光谱、色质联用分析对聚合反应机理进行了研究，讨论了聚合条件对聚合物分子量的影响，测定了聚合物的体外降解。     

苯乙烯-马来酸酐共聚物的生物降解性研究

合成了一系列苯乙烯．马来酸酐共聚物(SMA)。并对共聚物的结构进行了表征。用土埋法和CO2释放法研究了共聚物的生物降解性。探讨了分子量、组成、环境等因素对生物降解性的影响,发现共聚物的分子量降低。降解率增大;共聚物中马来酸酐含量提高。降解率增大;适宜的环境有利于生物降解。     

Enantioreversal in the sharpless asymmetric epoxidation reaction controlled by the molecular weight of a covalently appended achiral polymer

Polymers such as poly(ethylene glycol) (PEG) have proven use in a variety of applications including organic synthesis. We now disclose our investigations into the recently disputed report that PEG tartrate esters can reverse the enantioselectivity of the Sharpless asymmetric epoxidation reaction. The results presented herein have clarified that the enantioselectivity of this reaction can be reproducibly reversed solely as a function of the molecular weight of the appended PEG. By preparing a range of tartrate ligands with varying PEG chains lengths, the reversal was found to occur within a molecular weight change of only 800. As the PEG chain did not affect the inherent chirality of the ligand, the enantioreversal was proposed to occur as a result of two Ti-ligand complexes which differ in their molecularity of ligand, one monomeric in ligand and the other dimeric. Support for this hypothesis was given through equilibrium measurements which revealed that the predominant species in Ti/PEG tartrate ester mixtures is a distinct 2:1 Ti-ligand complex, as opposed to the 2:2 Ti-ligand complex of traditional Sharpless asymmetric epoxidations. In total, these data represent an unrecognized property of PEG-supported catalysts that could open up new venues in the control of asymmetric reactions by means of achiral appended polymers.     

Synthesis and Enzymatic Degradation of Nylon 66 Copolymers with Poly(Ethyleneglycol)s

Abstract

Nylon 66 (N66) copolymers were prepared by melt polycondensation of adipic acid and hexamethylenediamine with 5–80 mol% poly(ethylene glycol) (PEG), where the molecular weight (MW) of PEG was 200–1000. The reduced specific viscosity of the copolymers was increased by the copolymerization. The crystallinity and melting temperature (T _m) of N66 components decreased with increasing PEG content, but T _m depression of copolymers at the same mole content decreased with increasing MW of PEG, suggesting that the copolymer structures are not of the random type but of the block type at the higher MW of PEG. The water absorption increased with increasing PEG content, and its increase was much higher at the higher MW of PEG. The enzymatic degradation was estimated by the weight loss of copolymer films in the buffer solution with and without a lipase at 37°C. The weight loss was enhanced appreciably by the presence of a lipase, and increased abruptly at higher PEG content, which was correlated to water absorption and the concentration of ester linkages. The enzymatic degradation of these N66 copolymers was much higher than that of previously reported PET copolymers with PEG. The abrupt increase of weight loss by alkali hydrolysis was fairly comparable to that of water absorption.