PVA/PVP共混物的SAXS研究

聚乙烯醇(PVA)/聚吡咯烷酮(PVP)共混物的小角X-射线散射(SAXS)研究表明,PVA/PVP共混物的结构参数与共混物组分比及热历史密切相关。按Vonk一维电子密度相关函数法,得到PVA/PVP共混物的长周期,过渡层厚随PVP组分含量增加而增加;结晶片层厚和比内表面积却随PVP含量增加而降低。热处理可提高共混物的结晶性。     

聚乙烯醇/聚乙烯基吡咯烷酮共混体系的结晶行为

用DSC、WAXD和SAXS研究了聚乙烯醇(PVAl)/聚乙烯基吡咯烷酮(PVP)共混体系的结晶行为.PVAl的结晶度随PVP含量增加而减少,并存在结晶度为零的组成(PVAl)的重量分数约为50％.与纯PVAl相比,共混物的温度区间T_m-T_g减小,表明PVP对PVAl的结晶起抑制作用.共混物中PVAl的结晶速度下降,具体表现为PVAl过冷区随PVP含量增加而扩大,动力学速度常数减小,球晶增长速度下降.纯PVAl和共混体系的等温结晶速率均遵循Avrami方程.退火样品的长周期、片晶厚度和过渡层厚度大于相同组成未退火样品.两者长周期随PVP含量增长加显著增大,片晶厚度增长次之,过渡层厚度变化不大.     

聚乙烯醇/聚乙烯基吡咯烷酮共混体系相容性研究

用DSC、FTIR、SAXS和测定Flory-Huggins相互作用参数等方法对聚乙二醇(PVA1)/聚乙烯基吡咯烷酮(PVP)共混体系的研究。结果表明,该体系具有完全互容的性质。共混物只有一个玻璃化转变温度。用DMSO作溶剂浇铸的膜光学透明。PVA1的长周期和片晶厚度均随PVP含量增加而增大,但后者增大的幅度比前者小得多,表明PVP和PVA1的非晶部分形成均相并夹入到球晶内部。共混物中PVP羰基吸收峰和PVA1的羟基吸收峰与相应均聚物相比,在红外光谱图中皆向低频方向迁移,迁移波数随第二组分含量的增加而增大。表明二者间有氢键生成。用平衡熔点计算的Flory-Huggins相互作用参数为-0.88。     

对羟基苯甲酸(PHB)聚对苯二甲酸乙二酯(PET)液晶共聚酯和聚对苯二甲酸乙二酯共混物的酯交换表征

在温度280℃附近对含有液晶共聚酯P-Hydroxy Benzoic Acid/Poly(-Ethylene Terephthalate-)PHB/PET和Poly(-Ethylene Terephthalate-)PET的共混样品进行热处理时,发现共混物的熔点随热处理的时间增加而不断降低,热处理温度越高,相同时间内共混物熔点下降程度越大;而具有相同热历史的纯PET样品熔点几乎保持不变.通过NMR方法证实了PHB/PET-TET共混物熔点随热处理时间下降是由于PHB/PET和PET之间发生了酯交换反应.所以可根据共混物的宏观热性质和PHB/PET序列结构变化表征PHB/PET和PET共混物之间的酯交换程度.     

聚降冰片烯/聚乳酸共混物形状记忆效应的研究

将聚降冰片烯(PNB)和聚乳酸(PLA)按照PNB/PLA(80/20)、(70/30)、(60/40)、(50/50)4种不同质量配比进行共混,采用X射线衍射(XRD)、动态力学分析(DMA)、示差扫描量热分析(DSC)等对共混物基本性能进行表征,同时采用DMA-Q800对其形状记忆效应进行探究.结果显示:4种共混物均有明显屈服现象,随着PLA含量的增加,屈服现象越明显;PNB/PLA共混物出现2个玻璃化转变温度(T_g),且不随共混物配比变化而变化;4种共混物均在2θ=18.45o附近出现特征衍射峰,且其结晶度随PNB含量的减少而降低;随PNB含量的增多4种共混物的形状记忆性能提高.对于PNB/PLA(80/20),在双重形状记忆中,其形状固定率为99.88%,形状恢复率为81.04%;在三重形状记忆中,总固定率和恢复率分别为98.83%和94.26%.     

聚L-乳酸/4,4'-二羟基二苯硫醚共混物的分子间相互作用及结晶和熔融行为

利用红外吸收光谱(FTIR)研究了聚乳酸(PLLA)/4,4'-二羟基二苯硫醚(TDP)熔融共混物的分子间相互作用,结果表明,PLLA的羰基与TDP的羟基之间形成了分子间氢键.通过差示扫描量热(DSC)研究了共混物的玻璃化转变行为及非等温结晶和熔融行为.结果表明,样品的玻璃化转变温度(Tg)随TDP含量的增加呈线性下降.共混物的熔融结晶温度(Tc)、结晶焓(ΔHc)、熔融温度(Tm)及熔融焓(ΔHm)均随TDP含量的增加呈下降趋势,而冷结晶温度的变化趋势则相反.当TDP达到40%(质量分数)时,共混物的DSC曲线既未出现结晶峰,也未出现熔融峰,表明该样品已完全成为非晶态物质.广角X射线衍射(WAXD)分析结果表明,TDP的加入未改变PLLA的晶型,但导致其晶面间距变大,晶体结构变得松散.因此共混物熔点的下降归因于分子间氢键的形成降低了PLLA分子链的运动能力及晶体的紧密程度而非晶型的改变.     

壳-核结构增韧剂超高增韧非晶共聚酯的形貌和形态

研究了马来酸酐接枝的壳核结构增韧剂 (TPEg)对非晶热塑共聚酯 (PETG)的增韧和增强效果 ,并与马来酸酐接枝的纯橡胶类增韧剂 (POEg)作了对比 .TPEg对PETG具有显著的增韧效果 ,当TPEg含量由 5%增加到 1 0 %时 ,共混物就可以发生由脆性到超高韧性的快速转变 .而POEg虽然也可以使PETG发生由脆性到韧性的快速转变 ,但转变是在较高的增韧剂含量下发生的 ,这意味着共混物的抗张强度和模量损失更多 .利用扫描电镜观察、分析了随增韧剂含量的增加 ,共混物的形貌、形态的演化过程 .共混物的缺口冲击韧性与其形貌、形态之间存在很好的对应关系 .     

乙丙共聚物及其共混物晶型探讨

用广角X-射线衍射(WAXD)和偏光显微镜(PLM)方法,研究了具有乙丙长序列乙丙共聚物及其共混物,发现通过熔融慢冷结晶样品,C_3含量在30mol％以上,衍射角2θ=20°处出现了属于γ-PP晶型的(140),(130)晶面衍射。含有乙丙长序列链结构的乙丙共聚物及共混物属(α+γ)混晶结构;含乙丙长序列的EPR以γ-相为主,嵌段物和共混物则以α-PP为主,形成γ-PP结构的必要条件是含有乙丙长序列链结构样品熔融慢冷结晶。     

κ-型卡拉胶/聚乙烯吡咯烷酮共混水凝胶的辐射制备及性质研究

采用辐射技术制备了κ-型卡拉胶 ( KC) /聚乙烯基吡咯烷酮 ( PVP)共混水凝胶 ,研究了共混凝胶内 KC含量、PVP的分子量和辐照剂量等对 KC/ PVP共混水凝胶性质的影响 .实验发现 ,KC与高分子量的 PVP( k-90 )共混后在一定剂量范围内辐照可得到高强度、高溶胀行为的 KC/ PVP共混水凝胶 ,随着共混凝胶内KC含量的增加 ,凝胶强度及溶胀性能均显著提高 .分析表明 ,KC与高分子量的 PVP共混后 ,在较低剂量下 KC的降解被抑制 ,从而获得一种由物理交联的 KC和化学交联的 PVP形成的互穿网络 ( IPN)凝胶 .     

聚(ε-己内酯)/苯乙烯-丙烯腈共聚物共混物的形态研究

本文研究了聚(ε-己内酯)(PCI/苯乙烯-丙烯腈共聚物(SAN)共混物的形态。采用差示扫描量热计(DSC)测量了PCL/SAN共混物中的PCL结晶度随着SAN含量的增加而下降;当SAN浓度达到60wt％。以上时,PCI的结晶度趋于零。通过偏光显微镜可以观察到在含高浓度PCI的共混物中,PCL是以球晶形式存在的。样品是由PCL球晶充满的,但是随着SAN含量的增加,PCL球晶半径减小,球晶结构逐渐变得不规整,而X-射线衍射测试了不同组成的PCL/SAN共混物中PCL的晶胞参数没有改变,说明SAN没有进入到PCL的晶胞内。以小角X-射线散射结果发现PCI片晶之间的距离随着SAN含量的增加而增大。以上说明SAN分子与没有结晶的PCL形成无定形相夹在PCL的片晶之间。     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.