聚乙烯片晶辐照破坏机理的电子显微镜研究

用透射电子显微镜观察了高密度辐照聚乙烯的形态结构,并通过统计方法定量地分析了其结构与辐照剂量的关系。发现室温辐照聚乙烯的片晶形态不随辐照剂量而变化。若将室温辐照聚乙烯重新熔融,然后再于125℃下等温结晶4h后,其片晶厚度则随辐照剂量的增加而变薄,长周期亦随之变短。小角X射线散射的测试结果与上述结果符合得很好。室温辐照聚乙烯及其125℃重结晶试样的电子显微镜数据从又一直观角度验证了辐照聚乙烯“片晶内部破坏机理”的正确性。     

Wide-and small-angle x-ray scattering studies on the real structure of fractions of (ethylene-α-olefine)-copolymers

Fractions according to the degree of branching of (Ethylene/1-Buten)-Copolymer (LLDPE) were investigated by wide-and small-angle scattering. The thickness of the crystallites is nearly independent of the degree of branching and their volumes reach a limit according to the smallest stable crystal. The mean lattice disfortions also do not change remarkably with the degree of branching but the components of theg _ik tensors do so. The possibility of partial incorporation of side groups into the crystal lattice is discussed. Comparison of wide-and small-angle scattering shows that only the part of the crystallites with smaller thickness builds lamellar clusters while thicker ones are individual crystals.Dedicated to Prof. Dr. W.Pechhold on the occasion of his 60th birthday     

Preparation and interfacial properties of a novel biodegradable polymer surfactant: poly(ethylene oxide monooleate-block-DL-lactide)

In this paper, we report a novel synthesis of poly(ethylene oxide monooleate-block-DL-lactide) (MOPEO-PLA) in the presence of stannous 2-ethylhexanoate catalyst. By utilizing the surfactant property and the reactive double bond of the amphiphilic MOPEO-PLA, various characteristics of PLA microspheres, such as surface and internal structure, surface morphology, release property, and so on, may potentially be controlled. MOPEO-PLA was found to be hydrophobic enough to prevent loss by dissolution into aqueous solution, which is often a problem for MOPEO. Furthermore, the interfacial tension measurements of a MOPEO-PLA/toluene/water system revealed that MOPEO-PLA had a good surface activity almost equal to that of MOPEO. The MOPEO-PLA/PLA blend films were prepared by solvent casting on a water layer. Contact-angle measurements of MOPEO-PLA/PLA blend films confirmed that the hydrophilic PEO segments were selectivity accumulated at the oil/water interface. Moreover, the surface free energy on the 'water side' of the MOPEO-PLA/PLA blend films was increased because of the increase in polar components as a result of the ether bonds of the PEO segments. Schematic illustration of the adsorption property of a) MOPEO-PLA with a high-molecular-weight PLA segment and b) MOPEO-PLA with a low-molecular-weight PLA segment at an ethyl acetate/water interface.     

Langmuir monolayers from perfluorobutyl-n-eicosane

Perfluorobutyl-n-eicosane (abbreviated as F4H20) was spread at the air/water as Langmuir monolayers and studied under different experimental conditions, such as spreading volume, subphase temperature and compression speed. The Langmuir monolayer experiments (π-A isotherms) have been complemented with Brewster angle microscopy results, which enabled direct visualization of the monolayers’ structure and estimation of the film thickness at different stages of compression. It has been found that the molecules are oriented almost vertically (with respect to the interface) in the vicinity of film collapse. The negative sign of the measured surface potential, ΔV, is evidence for the orientation of F4H20 molecules with their perfluorinated parts exposed towards the air. In the case of F4H20 a limited fluorination relative to perfluoroeicosane also results in monolayer formation, in contrast to eicosane itself, which forms lenses.     

聚苯醚羧酸盐的聚集态结构

本文用热学、力学和散射方法研完了聚苯醚羧酸盐的链结构、羧化聚苯醚(C-PPO)在二氧六环溶液中用0.5 NaOH或CsOH的醇水溶液中和成钠型或铯型的C-PPO离聚体,用DSC测定一系列羧酸盐含量的C-PPO离聚体的玻璃化转变温度得到形成离子微区的临界阳离子浓度约为5mol％;动态力学谱中在高于玻璃化转变温度域出现的α松弛峰亦证明了微相结构的存在;SAXS结果表明其离子微区的尺寸约为30(?),其尺寸大小和离聚体中阳离子浓度无     

On the solid-state conformations of 18-crown-6 complexes

A procedure for displaying macrocylic torsion angles as a map on polar coordinates is discussed with reference to the solid-state conformations of l8-crown-6 and its complexes. The maps aid in comparisons of related structures, in the perception of pseudo-symmetry elements, and in the classification of the conformations of 18-crown-6. Only four conformational groups are found in the 1 : 1 complexes of 18-crown-6 with sodium, potassium, rubidium, cesium, thallium(I), calcium and strontium cations. The relationship of donor number, mean cavity radius and effective ionic radius combined with skeletal drawings of the donors and the polar map of the torsion angles provide a composite picture of the structures and insight into the balance between cation-donor interaction energy and conformational energy.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Three-phase capillary entry conditions in pores of noncircular cross-section

In this work we challenge the assumption that the capillary entry pressures for displacements in three-phase flow are the same as those in two-phase flow. Using an energy balance, as derived by R.P. Mayer and R.A. Stowe (J. Colloid Interface Sci. 20 (1965) 893-911) and H.M. Princen (J. Colloid Interface Sci. 30 (1969) 69-75; 30 (1969) 359-371; 34 (1970) 171-184) for two-phase flow, we derive a general formula for determination of the capillary entry pressures for piston-like displacement of two bulk phases in a pore where a third phase may also be present. The method applies to capillaries of angular cross-section and uniform but arbitrary wettability. To use this method we have determined all possible underlying phase occupancies in cross-sections on either side of the main terminal meniscus, in particular the presence of corner arc menisci (AMs). Indeed, the capillary entry pressures for piston-like displacements depend on the pressure in the remaining third phase if the cross-sectional fluid configurations contain this phase. This dependence only vanishes when layers of the intermediate-wetting phase completely separate the wetting and the non-wetting phases. The complexity of the corresponding equations and the quantitative effects are studied using two different geometries, the equilateral triangle and the rhombus. The main difference is that the latter geometry has unequal corners, which may carry different AMs. We have carried out a limited sensitivity study with respect to the effect of wettability, the spreading coefficient of the intermediate-wetting phase, and the aspect ratio of the principal radii of the rhombus.     

Synthesis and properties of poly(aryl ether ether ketone) copolymers with pendant methyl groups

Polyether ether ketone and polyether ether ketone copolymers were prepared by the nucleophilic substitution reaction of 4,4′-difluorobenzophenone with hydroquinone and with varying mole proportions of hydroquinone and methyl hydroquinone using sulfolane solvent in the presence of anhydrous K₂CO₃. The polymers were characterised by different physico-chemical techniques. The crystallinity of the polymers was found to decrease with increase in concentration of the methyl hydroquinone units in the polymer. Thermogravimetric studies showed that all the polymers were stable upto 430 °C with a char yield above 49% at 900 °C in N₂ atmosphere. The glass transition temperature was found to increase and the crystalline melting temperature and activation energy were found to decrease with increase in concentration of the methyl hydroquinone units in the polymer.     

Effect of glucocorticoids and their complexes with apolipoprotein A‐I on the secondary structure of eukaryotic DNA

The tetrahydrocortisol–apolipoprotein A‐I complex specifically interacts with eukaryotic DNA isolated from rat liver. This interaction is highly cooperative and of a saturating nature. One DNA molecule binds about 54 molecules of the complex. Small‐angle X‐ray scattering has shown that hydrogen bonds between nitrous bases are destroyed and that single‐stranded structures are formed at the interaction of the tetrahydrocortisol–apolipoprotein A‐I complex with eukaryotic DNA. The most probable site of binding the tetrahydrocortisol–apolipoprotein A‐I complex with DNA is the sequence of the CC(GCC)_n type entering the structure of many genes, among them the structure of the human apolipoprotein A‐I gene. Oligonucleotide of this type has been synthesized. The association constant (K_ass) of its complexation was shown to be 1.66 · 10⁶ M^?1. Substitution of tetrahydrocortisol for cortisol in the complex results in a considerable decrease of K_ass. IR‐spectroscopy study has shown that the interaction of tetrahydrocortisol with oligonucleotide CC(GCC)_3–5 is accompanied by the formation of hydrogen bonds via the CO‐NH, PO₂, and OH groups of desoxycytidinephosphate. The tetrahydrocortisol–apolipoprotein A‐I complex alters the DNA secondary structure formed at the interaction with the hormone, causing the structural transition “order → tangle.” It is assumed that in the GC‐pairs of the given DNA sequence, tetrahydrocortisol initiates the rupture of hydrogen bonds, while the hydrophobic interactions between nitrous bases and apoA‐I intensify this process. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Ammonia Catalyzed Hydrolysis-Condensation Kinetics of Tetraethoxysilane/Dimethyldiethoxysilane Mixtures Studied by <Superscript><Emphasis Type="Bold">29</Emphasis></Superscript>Si NMR and SAXS

In-situ ²⁹Si liquid-state nuclear magnetic resonance (NMR) was used to investigate the ammonia catalyzed hydrolysis and condensation of the mixed systems of tetraethoxysilane (TEOS) and dimethyldiethoxysilane (DDS) dissolved in methanol. With ammonia catalysis, the hydrolysis reaction orders for TEOS and DDS in the mixed systems remained first order, which is similar to that observed for their corresponding single silane component precursor systems. The hydrolysis rate constant for TEOS in the mixed systems was larger than that of TEOS in the single silane component precursor systems. Meanwhile, the hydrolysis rate constants of DDS in the mixed precursor systems were smaller than those of DDS in the single silane component precursor systems. The hydrolysis and condensation kinetics showed more compatible hydrolysis-condensation relative rates between TEOS and DDS, which remarkably affected the final microstructure of the resulting silica particles. Small angle X-ray scattering (SAXS) experiments showed a typical double fractal structure in the particulate networks.