PLA,PPC和PHBV共混物的热性能、力学性能和生物降解性能研究

将聚乳酸(PLA)、聚碳酸酯(PPC)及β-羟基丁酸酯与β-羟基戊酸酯共聚物(PHBV)以溶液浇注法制备了各种不同比例的共混膜(60/20/20,40/20/40,40/40/20,20/60/20,20/40/40,20/20/60)。采用示差扫描量热分析(DSC)和热重分析(TG)研究了共混物的热性能,采用万能材料试验机研究了共混物的力学性能,通过土壤悬浊拟环境降解实验和扫描电子显微镜(SEM)研究了共混材料的环境生物降解性能。结果显示,该三元共混体系是部分相容的体系,PLA增加了材料的强度,PPC增加了材料的断裂伸长,PHBV则提高了材料的环境生物降解速率,三者优势互补,是一种有应用前景的生物降解共混体系。     

离子液体增塑改性玉米淀粉/聚丁二酸丁二醇酯共混材料的结构与性能

为考察离子液体对淀粉/聚丁二酸丁二醇酯(PBS)的作用效果,降低淀粉/PBS的脆性,以离子液体(1-丁基-3-甲基咪唑氯盐[BMIM]Cl)作为增塑改性剂通过熔融共混法制备了玉米淀粉/聚丁二酸丁二醇酯(PBS)共混材料,采用红外光谱(FTIR)、扫描电镜(SEM)、热重分析(TGA)、X射线衍射分析(XRD)及力学性能测试方法研究了[BMIM]Cl对淀粉/PBS共混材料结构和性能的影响.结果表明,[BMIM]Cl能与淀粉/PBS分子发生强相互作用,破坏淀粉/PBS共混物中原有的氢键与结晶结构,增强界面相互作用,改善相容性,进而改变淀粉/PBS共混材料的结构与性能;[BMIM]Cl的加入不影响淀粉/PBS的热稳定性,可使材料玻璃化转变温度(Tg)、结晶温度(Tc)、冷结晶温度(Tcc)及结晶度(Xc)降低.[BMIM]Cl具有显著降低淀粉/PBS脆性的作用,使其断裂伸长率大幅度增加,拉伸强度和弹性模量降低.     

流场中聚乳酸/聚碳酸酯共混体系的酯交换反应及其形态结构研究

选用钛酸四丁酯作为聚乳酸(PLA)/聚碳酸酯(PC)的酯交换反应催化剂,通过透射电子显微镜(TEM)和核磁共振氢谱(1H-NMR)研究了流场中不同组分比的PLA/PC共混体系酯交换反应机理及酯交换反应对不同组分比的共混体系相形态的影响.研究发现,无论在PLA/PC共混体系中是否含有催化剂,酯交换反应次数、参与酯交换反应的PC的含量、生成的共聚物中PC链段的含量及生成的共聚物的总质量和总摩尔数均随组分中PLA含量的增加而增加,催化剂的加入更拉大了这种差距.主要原因是与PC作为连续相相比,当PLA作为连续相时PLA链段沿界面的取向程度更高,从而导致进行多次酯交换反应的几率增加.添加催化剂后,影响酯交换反应的主导因素发生变化,从而导致PLA/PC 30/70体系界面反应的机理发生改变.钛酸四丁酯有效地促进了PLA/PC体系的酯交换反应,使分散相的尺寸都得到不同程度降低,尤其当PLA为连续相时催化产生的共聚物的总摩尔数更多,从而使PLA为连续相时的分散相粒径较PC为连续相时降低的更多.     

钛酸酯催化碳酸二甲酯与苯酚酯交换反应的研究

用Ti(OBu)4、Ti[OCH(CH3)2]4和T(OPh)43种钛酸酯作催化剂,对碳酸二甲酯（DMC）与苯酯的酯交换反应进行了研究。以Ti(OBu)4为催化剂,对反应的热力学、原料配比、催化剂用量、反应温度和反应时间等工艺条件进行了考察 。实验表明,当DMC：苯酚：Ti(OBu)4(摩尔比）＝1.5:1:0.05、反应温度175℃、反应时间为25h时,酯交换反应基本上达到平衡,苯酚的转化率为47.4％,MPC的选择性为90.9%,DPC的选择性为9.14%.     

微生物合成的β-羟基丁酸酯与β-羟基己酸酯共聚物/聚乳酸共混材料(PHBHHx/PLA)的力学性能与生物降解性研究

通过熔融共混法制备了聚乳酸/微生物产β-羟基丁酸酯与β-羟基己酸共聚物的共混物(PLA/PHBHHx)。采用拉伸力学试验研究了共混物的力学性能。通过土壤悬浊培养降解法和扫描电子显微镜(SEM)分析对共混材料的生物降解性能进行了研究。实验结果表明,随着PHBHHx含量的增加,共混物的拉伸强度和杨氏模量降低,而生物降解速率却显著提高。但是,在175h之前,重量组成比为20/80的共混物降解速率比纯PHBHHx还要快。综合分析表明,共混材料PLA/PHBHHx的重量比为20/80时,具有优良的力学性能和生物降解性。     

甲酰胺对介孔N-TiO2微结构及光催化性能的影响

以钛酸四丁酯为前躯体,甲酰胺为氮源,采用溶胶凝胶法制备了具有可见光活性氮掺杂二氧化钛(N-TiO2)光催化剂.通过XPS、XRD、低温N2吸附.脱附和UV-Vis等表征,考察甲酰胺加入量对样品微结构和可见光活性的影响.当甲酰胺与钛酸四丁酯的物质的量的比为2、4、8、13时,制备的样品晶粒粒径在8～12 nm范围内,孔径在9～16咖范围内,孔隙率在54%～63%之间.甲酰胺与钛酸四丁酯的物质的量的比为13时,所制备样品具有较强的可见光吸收性能,其最大吸收边扩展到570 nm左右,禁带宽度减小至2.18 eV,比纯二氧化钛禁带宽度3.20 eV降低了1.02 eV.结果表明:随着甲酰胺加入量的增加,样品的晶粒粒径、孔径、孔隙率明显变大,禁带宽度减小.对甲基橙的室内自然光降解实验证明.氮掺杂二氧化钛具有良好的光催化活性,当甲酰胺与钛酸四丁酯的物质的量的比为13时,催化剂对甲基橙的降解率最高,为98.3%.     

接枝聚乳酸/塑化淀粉共混物的制备与性能研究

为提高聚乳酸(PLA)/淀粉共混物界面作用和降低成本,引入甲基丙烯酸缩水甘油酯(GMA)接枝聚乳酸和塑化淀粉(TPS),通过挤出和注射成型制备接枝聚乳酸/塑化淀粉共混物(PLA-g-GMA/TPS)。红外光谱分析证实,GMA成功接枝到PLA分子链上。对共混物的力学性能、热机械性能、微观形貌、热性能及亲水性等进行了系统研究,结果表明,选择GMA用量为6%(接枝率为1.51%)和TPS用量为10%时的拉伸强度、断裂伸长率及弹性模量最佳,分别为42.6MPa、8.9%及260MPa。FE-SEM观察结果表明,低含量TPS中颗粒被基体包覆或嵌入,界面平整,界面结合力强。DMA和DSC结果显示,不同质量配比的PLA-g-6%GMA/TPS共混物的Tg、储存模量、结晶度、结晶温度及熔融温度仅在小范围内发生变化。吸水率和接触角结果表明,低含量TPS的共混物吸水率和接触角变化幅度均小于高含量TPS体系。     

环氧呋喃树脂反应性增容改性聚乳酸/淀粉复合材料的研究

研究了环氧呋喃树脂反应增容改性聚乳酸/淀粉复合材料,对索氏提取法得到的淀粉进行1H-NMR、FTIR、XPS和静态接触角测试表征.结果表明在熔融共混过程中环氧呋喃树脂(FER)与淀粉及聚乳酸(PLA)发生化学反应,从而起到反应性增容的作用.另外,利用SEM、万能材料试验机和DSC分别对复合材料的界面相容性、机械性能以及热性能进行了表征,结果表明FER能够显著改善PLA和淀粉之间的界面相容性,在保持PLA高强度高模量的基础上,显著提高了PLA/starch复合材料的综合机械性能和结晶性能.     

微生物合成的β-羟基丁酸酯与β-羟基已酸酯共聚物/聚乳酸共混材料(PHBHHx/PLA)的力学性能与生物降解性研究

通过熔融共混法制备了聚乳酸/微生物产β-羟基丁酸酯与β-羟基己酸共聚物的共混物(PLA/PHBHHx).采用拉伸力学试验研究了共混物的力学性能.通过土壤悬浊培养降解法和扫描电子显微镜(SEM)分析对共混材料的生物降解性能进行了研究.实验结果表明,随着PHBHHx含量的增加,共混物的拉伸强度和杨氏模量降低,而生物降解速率却显著提高.但是,在175h之前,重量组成比为20/80的共混物降解速率比纯PHBHHx还要快.综合分析表明,共混材料PLA/PHBHHx的重量比为20/80时,具有优良的力学性能和生物降解性.     

聚乳酸-木粉-甲基丙烯酸缩水甘油酯接枝乙烯辛烯共聚物复合材料的制备及性能

选用甲基丙烯酸缩水甘油酯接枝乙烯辛烯共聚物(POE-GMA)和聚乳酸、木粉在Haake转矩流变仪中熔融共混.通过拉伸、冲击、差示扫描量热、扫描电镜等测试方法对共混复合材料的性能进行了研究.结果表明:聚乳酸木塑复合材料的拉伸强度和弯曲性能随POE-GMA添加量的增加而减小；POE-GMA的加入使聚乳酸木塑复合材料的结晶温度下降,结晶度升高；当m(PLA)∶m(WF)∶m(POE-GMA)=80∶20∶20时,复合材料的表面自由能最低,接触角最大,吸水性最低；随着木粉含量的增加,复合材料的起始热降解温度降低,POE-GMA的含量增加对聚乳酸木塑复合材料的起始热降解温度影响不大.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.