Preparation of HPMC–EA–DMAEMA nanosized latex

Nanosized copolymer latex of hydroxypropylmethylcellulose (HPMC) grafted with ethyl acrylate (EA) and dimethylaminoethyl methacrylate (DMAEMA) has been prepared by acidifying submicron-sized latex particles synthesized by soap-free emulsion graft copolymerization using potassium persulfate (KPS) as initiator. The effects on the diameter of the latex particles of different conditions, for example concentration of DMAEMA, amount of HPMC, and ratio of HCl to DMAEMA for acidification, were investigated. It was found that increasing the mole ratio of HCl to DMAEMA to 1.0 and increasing the DMAEMA content both resulted in a decrease in particle diameter, whereas increasing the amount of HPMC resulted in larger particle sizes. Measurement by dynamic light scattering (DLS) revealed the diameter of the latex particles was >200 nm before acidification and <100 nm after acidification. Evidence of grafting was obtained by use of Fourier transform infrared (FTIR) spectroscopy. Transmission electron microscopy (TEM) was used to characterize the morphology of the copolymer particles before and after acidification.     

Influence of thermal and thermo-mechanical treatment

Two lipids with similar melting ranges but of different composition were analyzed using differential scanning calorimetry and X-ray diffraction. The lipids were processed via extrusion or were tempered at different temperatures; they were analyzed directly after extrusion and after storage at 40°C. Precirol ATO 5® showed high sensitivity to storage time and varied temperature exposure. Extrusion showed only marginal influences on the solid state. Melting peaks were narrower and shifted to higher temperatures in comparison to the untreated powder. Dynasan 114® was more robust, changes in the solid state could only be shown for samples treated above the melting range. Thus, Dynasan 114® is more appropriate for solid lipid extrusion of pharmaceutical products.     

Calorimetric approach to tetronic/water interactions

Tetronic^®comprises X-shaped copolymers formed by four poly(propylene oxide) (PPO) andpoly(ethylene oxide) (PEO) block chains bonded to an ethylene diamine centralgroup. Micellization behaviour of three representative Tetronics (T304, T904and T1307) was characterized to gain an insight into the interactions betweenthe copolymer unimers and the state of water in their solutions. The enthalpyof demicellization, recorded at 37°C in an isoperibol microcalorimeter,indicated that the process was in all cases exothermic and the enthalpy rankedin the order T1307≥T904>>T304. Micellization is entropy-driven owing tohydrophobic interactions between the PPO chains.DSC analysisshowed that the crystallization and melting peaks of the free water remainingin T304 and T904 solutions were progressively shifted toward lower temperaturesas the surfactant proportion increased, owing to a colligative effect. Boundwater corresponded to 3 water molecules per EO repeating unit. In the caseof T1307, which has longer PEO chains, a splitting of the melting peak wasobserved, one peak appearing around 0°C due to free water and anotherat –15°C due to interfacial water. As T1307 proportion raised, theenthalpy of the former decreased, whilst the enthalpy of the latter increased.In 40% T1307 solutions, interfacial water overcame the proportion of freewater; there being 1 interfacial and 3 bound water molecules per EO repeatingunit. Gaussian deconvolution of FTIR spectra also enabled to characterizethe evolution of free water as a function of Tetronic proportion. The dependenceof micellization and water interaction behaviour on Tetronics structure shouldbe taken into account to use these copolymers as drug solubilizers and micellarcarriers.     

n型砷化镓微区光电化学腐蚀过程

在n-GaAs电解液界面,用聚焦He-Ne激光照射, 使n-GaAs表面发生微区光电化学腐蚀, 用计算机控制步进马达, 使试样在X-Y二维方向扫描移动, 能在晶片上得到刻蚀点直径2 μm的刻蚀图案. 研究了激光相对光强, KOH、H_2SO_4、KCl等刻蚀剡的浓度, 光腐蚀的时间, 电极电位等因素对腐蚀点的直径和深度的影响, 通过实验数据找出腐蚀过程的规律, 并用光电化学原理进行解释.     

DNA intercalating studies of [Ru(bpy)<Subscript>2</Subscript>HPIP]<Superscript>2+</Superscript> with intramolecular hydrogen bond ligand based on introduction of copper ion

The effects of copper ion on the interaction of [Ru(bpy)₂HPIP]²⁺(bpy = 2,2′-bipyridine, HPIP = 2-(2-hydroxyphenyl) imidazo [4,5-f] [1, 10] phenanthroline) with DNA have been investigated by electronic absorption spectroscopy and fluorescence spectroscopy. HPIP ligand of the complex with an intramolecular hydrogen bond can bind Cu²⁺ in the absence of DNA, as revealed by the absorbance and fluorescence decrease for [Ru(bpy)₂HPIP]²⁺. The resultant heterometallic complex binds to DNA via intercalation of HPIP into the DNA base pairs and its DNA-binding ability is stronger than [Ru(bpy)₂HPIP]²⁺ itself. The DNA bound [Ru(bpy)₂HPIP]²⁺ cannot bind Cu²⁺ at low Cu²⁺ concentration and the intramolecular hydrogen bond in HPIP is located inside the DNA helix. While the Cu²⁺ concentration is relative high, Cu²⁺ can quench the fluorescence of DNA bound [Ru(bpy)₂HPIP]²⁺. The quenching reason is proposed.     

细胞色素C的电化学行为研究

本文评述了细胞色素Ｃ电化学研究的发展概况，重点介绍了细胞色素Ｃ在促进剂作用下的电化学行为，促进剂种类，影响促进作用的因素及促进机理。     

Structural Study of Silica Xerogel Composites Containing Pd Aggregates

Composites containing Pd aggregates dispersed in amorphous silica are of interest from both a fundamental and applied point of view because of their attractive catalytic properties. The silica powders added with palladium, prepared by the sol-gel method, were studied using X-ray diffraction, and IR- and UV-Vis-spectrophotometry. Silica xerogel samples were prepared using a ethanol/H₂O/TEOS molar ratio of 4:11.6:1 and loaded with sodium tetrachloropalladate. The silica xerogel microstructure of the powders was studied as a function of annealing temperature. Attention was paid to the evolution of the glass matrix as well as the palladium aggregates in the SiO₂ matrix. We found in our samples partial crystallization of the glass matrix in form of quartz and cristobalite phases with palladium oxide and metallic palladium phase at 1000^∘C. The Rietveld refinement method was used in order to determine the percentage of the phase contents.     

用会聚偏振光测定双轴热拉伸有机玻璃板的双折射值的研究

介绍了用会聚偏振光测定双轴热拉伸定向有机玻璃板双折射值的原理和实验方法,并提出了对Kramer计算公式的简化和改进。测定了双折射值与拉伸度、拉伸温度的关系并分析了干涉图。     

Synthesis and in vivo study of metallofullerene based MRI contrast agent

Gd@C₈₂(OH)₄₀ has been developed as a new generation of MRI contrast agent. But recently, it was found that Gd@C₈₂(OH) _x with a larger number of OH (x>36) would lead to cage break and hence, release of highly toxic Gd ions. We synthesized the more stable Gd@C₈₂(OH) _x with less OH-number, Gd@C₈₂(OH)₁₆, and studied its proton relaxivity and MRI images. The results indicate that Gd@C₈₂(OH)₁₆ also gives high proton relaxivity, even higher than that of (NMG)₂-Gd-DTPA. The bio-distribution indicated that Gd@C₈₂(OH)₁₆ tends to be entrapped in the liver and kidney and remained in tissue for about 2 hours. The results suggest that the more stable metallofullerene derivative Gd@C₈₂(OH)₁₆ can be the potential candidate of the new MRI contrast agent.     

Macroporous poly(methyl methacrylate) produced by phase separation during polymerisation in solution

Polymethyl methacrylate (PMMA) sponges were obtained by polymerization in a solution with monomer/ethanol ratios up to 20:80. The material obtained after the elimination of the solvent present a homogeneous distribution of dispersed pores up to a monomer/ethanol ratio lower than 40:60. For higher ethanol contents in the reacting mixture, the morphology of the sponge corresponds to a network of PMMA microparticles, leaving large empty spaces leading to highly porous structure. The monomer/ethanol ratio during polymerization has a large influence on the porosity, thermal, and mechanical properties of the material and, for large solvent contents, on the size of the polymer microparticles.