六甲氧基甲基三聚氰胺-多元醇-丙烯酸酯混杂聚合过程热互补效应的研究

六甲氧基甲基三聚氰胺（HMMM）－多元醇－丙烯酸酯－酸催化剂的混合体系在较高温度下同时进行缩聚和自由基聚合并表现出协同效应，DSC研究结果表明，丙烯酸酯在HMMM和酸的催化作用下可在较低温度下发生自由基聚合反应，并把反应释放出来的大量的热量有效地传递给缩聚发反应，满足缩聚反应吸热的要求，从而节省固化所需要的能量，为了提高储存稳定性。本文以潜酸催化剂作为酸的来源，对该混杂聚合体系进行了研究，仍有明显的热互补效应。     

聚合物系统中的传能和光化学

评论了聚合物系统中非辐射能量传递类型,影响能量传递的因素,以及能量传递同聚合物光化学的关系,附22篇文献。     

一类新型三线态敏化剂光物理行为的研究

本文对一类新型的三线态敏化剂N-甲基芳酰基甲基-β-萘骈噻唑啉的光物理行为进行了研究。测定了它们的吸收光谱、荧光和燐光量子产率。发现所研究的敏化剂比常用敏化剂有着较高的克分子吸收系数(～10~4),还具有较高的系间窜跃能力。本文还测定了存在不同敏化剂时,芪的顺、反异构化反应速度,以此评价化合物的敏化效率。认为这类化合物是有效的新型光敏化剂。     

Synthesis, band structure, and optical properties of Ba2ZnV2O8

A novel compound Ba₂ZnV₂O₈ has been synthesized in high temperature solution reaction and its crystal structure has been characterized by means of single crystal X-ray diffraction analysis. It crystallizes in monoclinic system and belongs to space group P2₁/c with a=7.9050(16), b=16.149(3), , β=90.49(3). It builds up from 1-D branchy chains of [ZnV₂O₈⁴⁻]_∞, and the Ba²⁺ cations are located in the space among these chains. The IR spectrum, ultraviolet-visible diffuse reflection integral spectrum and fluorescent spectra of this compound have been investigated. The calculated results of energy band structure by the density functional theory method show that the solid-state compound of Ba₂ZnV₂O₈ is an insulator with direct band gap of 3.48 eV. The calculated total and partial density of states indicate that the top valence bands are contributions from the mixings of O-2p, V-3d, and Zn-3d states and low conduction bands mostly originate from unoccupied antibonding states between the V-3d and O-2p states. The V-O bonds are mostly covalence characters and Zn-O bonds are mostly ionic interactions, and the ionic interaction strength is stronger between the Ba-O than between the Zn-O. The refractive index of n_x, n_y, and n_z is estimated to be 1.7453, 1.7469, and 1.7126, respectively, at wavelength of 1060 nm for Ba₂ZnV₂O₈ crystal.     

Thermal analysis of polysiloxanes, aromatic polyimide and their blends

Low molecular weight poly(dimethylsiloxane) and poly(methylphenylsiloxane) were synthesized and blended with polyimide (PI) at its precursor poly(amic acid) stage. FTIR analysis has proven the retention of polysiloxanes in polyimide after the ultimate curing of blends. Differential scanning calorimetric analysis was performed on polysiloxanes to elucidate the structures present in polymers while thermogravimetric analysis (TGA) was performed on polysiloxanes, polyimide as well as their blends to evaluate the thermal stability and to analyze the effect of polysiloxane incorporation in blends. Blends have shown synergistic improvement as compared to neat polyimide.     

Study of metal-loaded activated charcoals for the separation and determination of selenium species by energy dispersive X-ray fluorescence analysis

Conversion of adsorption properties of activated charcoal (C^∗) by metal modification towards selenite, selenate and seleno-dl-methionine (Se-Met) was studied. Several metals were included in modification studies and also a procedure was developed for the separation and independent determination of microgram quantities of these selenium species in aqueous solution. Selenium species were collected one by one from the same sample solution onto collector material by adsorbing them directly or after complex formation onto different metal-loaded activated charcoals (MgC^∗ and FeC^∗). The mass of selenium in these collectors was measured directly by energy dispersive X-ray fluorescence spectrometry (EDXRF). Detection limits for all three selenium species were better than 6 μg corresponding to concentration of 60 μg/l with 0.100 l of initial sample volume.     

What crystals of small analogs are trying to tell us about cellulose structure

The molecular geometries from crystal structures of 23 small molecules such as cellobiose were reviewed and extrapolated to give model cellulose chains. Within a given model, all monosaccharide units and their linkages are identical so the models are regular helices. Despite fairly large ranges for the glycosidic linkage torsion angles and , 29° and 57°, respectively, there is little variation in the n and h parameters of the model helices. They are extended, with h values (the advance per residue along the helix axis) of 5.04–5.27 Å. Some models were slightly right-handed, with n values up to 2.12 residues per helix turn. Left-handed models were in the majority, and their n values were as large as –2.91. These results are consistent with known structures of cellulose and its derivatives. An exception comes from a heavily derivatized cellobiose molecule. It yields right-handed helices with n 4.5 and h 3 Å. Because one half turn of this helix reverses the direction of the chain in a compact region, the linkage geometry is a model for chain-folding. Other derivatives that are unable to form the O3O5 hydrogen bond gave left-handed helices. The puckering of the glucose rings was also surveyed. A number of rings in small molecule structures are puckered to a degree that is similar to the puckering determined for methyl cellotrioside, cellotetraose, cellulose I and cellulose II.     

A Theoretical Study on the Conductivity of Carbon Doped BNNT

From the changes in energy band, density of state (DOS) and electronic structure calculated by the DFT/B3LYP method, the conductivity of carbon doped boron‐nitride nanotube (BNNT), which is formed by C‐C bond substituting B‐N bond, was discussed. The results indicate that the substitution will strengthen the conductivity of the tube, and its semi‐conductivity might be adjusted by controlling the substitution.     

Synthesis of a novel rigid molecule family for the investigation of electron and energy transfer

Three new rigid bridging ligands for metal complexation (7=bmb, 8=bqb and 11=btb) were prepared from a rigid triptycene spacer connected to two bipyridine ligands using a Horner–Emmons type reaction. The triptycene spacer is substituted by methoxy groups in the case of bmb and in the case of bqb by a benzoquinone substituent. The corresponding metal complexes (ruthenium and/or osmium) were synthesised and the different luminescence behaviour was tested. They show great potential for the investigation of intramolecular electron and energy transfer reactions. The dinuclear metal complex Ru---bqb---Os is an interesting system in which the bridging ligand bqb acts as a redox switch, able to tune the conductivity for energy or electrons across the bridge.     

Spectrum analysis of U-doped LaBr3 single crystals. Part 1: crystal-field analysis

Single crystals of U³⁺:LaBr₃ were grown by the Bridgman-Stockbarger technique. High-resolution polarized absorption spectra of the crystals were recorded at 4.2 K in the 4000-50,000 cm⁻¹ range. Sixty-four experimental crystal-field energy levels of the U³⁺ ion were fitted to a semiempirical Hamiltonian employing free-ion, one-electron crystal-field as well as two-particle correlation crystal-field (CCF) operators with an r.m.s. deviation of 28 cm⁻¹. The performed analysis of the spectra enabled the determination of crystal-field parameters and assignment of the observed 5f³→5f³ transitions. The effects of selected CCF operators on the splitting of some specific U³⁺ multiplets have been investigated and the obtained values of Hamiltonian parameters are discussed and compared with those reported in previous analyses.