DETECTION OF T_g BY MODULATED DIFFERENTIAL SCANNING CALORIMETRY

The glassy transition of the polyethylene terephthalate (PET) sampleswhich have been subjected to solvent induced crystallization (SINC) was investigated bymodulated differential scanning calorimetry (MDSC) and density measurement. The dif-ferential of heat capacity signal, d C_p/dT from MDSC, was used to monitor the SINCprocess. It reveals that the T_g temperature shifts to higher value with the advancement ofSINC. When the toluene-immersing time was longer (168h), the detection of T_g becomemore difficult, because some smaller peaks emerged at the lower temperatures and theseare explained as the movement of small segments in the amorphous region. These observedresults are due to the morphology and structure introduced by the SINC process.     

羟基自由基引发的马来酸酐聚合反应机理AM1研究

用AM1方法计算了马来酸酐、羟基自由基及其加成产物α-羟基丁二酸酐基自由基的电子结构、电荷分布和键级.应用前线轨道理论和成键三原则研究了羟基自由基引发下马来酸酐聚合过程中α-羟基丁二酸酐基自由基活性中间体参与反应的可能性及其自由基聚合反应机理.计算结果表明:马来酸酐基态分子的HOMO和LUMO分别对应于双键CC的成键π-MO和反键π -MO;马来酸酐的羟基自由基加成反应活化能计算值为55 7kJ/mol;马来酸酐在羟基自由基引发下的自由基聚合产物是链式结构,与实验事实相符.     

Relationship between the molybdenum phases and the conversion of n-butane over Mo/HZSM-5

The conversion of n-C₄H₁₀ was undertaken on MoO₃/HZSM-5 catalyst at 773–973 K and the phases of molybdenum species were detected by XRD. The XRD results show that bulk MoO₃ on HZSM-5 can be readily reduced by n-C₄H₁₀ to MoO₂ at 773 K and MoO₂ can be gradually carburized to molybdenum carbide above 813 K. The molybdenum carbide formed from the carburization of MoO₂ with n-C₄H₁₀ below 893 K is -MoC_1−x with fcc-structure, while hcp-molybdenum carbide formed above 933 K. During the evolution of MoO₃ to MoO₂ (>773 K) or the carburization of MoO₂ to molybdenum carbide (>813 K), deep oxidation, cracking and coke deposition are serious, in particular at higher reaction temperatures, these lead to the poor selectivity to aromatics. Aromatization of n-C₄H₁₀ can proceed catalytically on both Mo₂C/HZSM-5 and MoO₂/HZSM-5, the distribution of the products for the two catalysts is similar below 813 K, but the activity for Mo₂C/HZSM-5 is much higher than that for MoO₂/HZSM-5.     

固相配位化学反应研究 L ⅩⅩⅢ.等温电导法研究醋酸锰和草酸的室温固相化学反应

本文利用等温电导法考察了醋酸锰和草酸的室温固相配位化学反应的制样方法对实验结果的影响，并获得了该反应的动力学参量。     

CRYSTAL AND MOLECULAR STRUCTURE OF THE COMPLEX OF METHOXYCARBONYLETHYLTIN TRICHLORIDE WITH SALICYLIDENE－M－TOLUIDINE

ＣＲＹＳＴＡＬＡＮＤＭＯＬＥＣＵＬＡＲＳＴＲＵＣＴＵＲＥＯＦＴＨＥＣＯＭＰＬＥＸＯＦＭＥＴＨＯＸＹＣＡＲＢＯＮＹＬＥＴＨＹＬＴＩＮＴＲＩＣＨＬＯＲＩＤＥＷＩＴＨＳＡＬＩＣＹＬＩＤＥＮＥ－Ｍ－ＴＯＬＵＩＤＩＮＥＦａｎｇＸｉｎＦＵ；ＸｉｕＪｕａｎＬＩ；Ｈ...     

Highly effective and recyclable dendritic ligands for the enantioselective aryl transfer reactions to aldehydes

[reaction: see text] A series of chiral pyrrolidinylmethanol-based dendritic ligands were synthesized for application in enantioselective aryl transfer reactions to aldehydes with the (ArBO)3/ZnEt2 system in up to 98% ee.     

聚醚氨酯的氧化及其接枝共聚合的研究

本文研究了在聚醚氨酯表面上进行接枝共聚合的新方法。首先在聚醚氨酯薄膜上通过过氧化氢光氧化引入过氧化氢基,然后在还原剂亚铁盐或N,N-二甲基对甲苯胺的作用下引发丙烯酰胺接枝共聚合,反应具有低温快速的特点。产物经吸水性实验及扫描电子显微镜观察均证实了是一接枝共聚物。通过模型化合物的研究证明,接枝反应具有较高的选择性,接枝共聚占优势地发生在聚醚软段上,接枝地点很可能就在醚键旁的α-碳原子上。     

Synthesis of poly(styrene-co-3-trimethoxysilyl propyl methacrylate) microspheres coated with polysiloxane layer

A procedure has been developed to coat micron-sized poly(styrene-co-3-trimethoxysilyl propyl methacrylate) microspheres with a smooth layer of polysiloxane by the hydrolysis and condensation of methyl trimethoxylsilane (MTMS). Firstly, polystyrene microspheres containing silanol groups were prepared by conventional dispersion polymerization using 3-(trimethoxysilyl) propyl methacrylate (MPS) as a functional comonomer in an ethanol/water medium. Secondly, the synthesis of the polysiloxane shell was carried out using a sol–gel process of MTMS. The thickness of the shells can be easily varied with different copolymer seeds and MTMS feed ratio. When we used copolymer particles with 2.00 μm diameter as seeds, the thickness of the polysiloxane shells can be varied from 0.10 to 0.18 μm. The core/shell structure of the composite microspheres was characterized by transmission electron microscope (TEM).     

UV-blocking property of dumbbell-shaped ZnO crystallites on cotton fabrics

A facile process to prepare uniform dumbbell-shaped ZnO crystallites was presented. The evidence in this Article discovered a unique morphological effect on the UV-blocking property. The as-prepared ZnO crystallites were characterized by XRD, HRTEM, FESEM, UV-blocking, and Raman scattering spectra. Our tentative investigation created a breakthrough to both the ultrahigh "Ultraviolet protection factor" (UPF) and the overall-range of complete UV-radiation blocking. Therefore, the as-prepared structural material demonstrated a significant advance in protective functional treatment and provided a potential commercialization.     

Ab initio Valence Bond Study on AB-type Molecules,A Description for XH(X=L,Be,B,C,N,O,F) and XF(X=Li,Be,B)

Ab initio valence bond method is employed to quantitatively study the concepts of ionic resonance energy and ionicity of a chemical bond in the cases of hydrides XH(X=Li,Be,B,C,N,O,F) and fluorides XF(X=Li,Be,B),By establishing the relationship between resonance and stability,and comparing the calculated ionicities with Pauling‘s earlier estimations in the above diatomic molecules,the merits of Pauling‘s classical resonance theory were demonstrated at the ab initio level.