INFLUENCE OF ESTER GROUP-SIZE IN PMAS ON BETA-PHASE CRYSTALLIZATION OF PVF2 IN HIGHLY ORIENTED FILMS OF PVF2/PMAS BLENDS

Influence of ester group size in polymethacrylates (PMAs) , including PMMA, PEMA and PBMA, on beta phase crystallization of poly(vinylidene fluoride) (PVF2) in highly oriented films of PVF2/PMAs=80/20 blends has been investigated by FTIR and TEM. The melt-drawn films of pure PVF2 consist of highly oriented lamellae, in which the alpha phase is predominant. Adding a given amount of PMAs (20 wt%) into PVF2 results in formation of fibrillar crystals and increase of relative amount of the beta phase. The influence extent is in order of PMMA > PEMA > PBMA, regarding the ester group size in the PMAs.

INVESTIGATIONS OF HYDROLYSIS KINETICS OF ATROPINE SULFATE BY ELECTROANALYSIS AT THE WATER NITROBENZENE INTERFACE

The hydrolysis kinetics of atropine sulphate has been investigated by cyclic voltammetry at the water/nitrobenzene interface. The transfer process is diffusion controlled and the transfer species is a 1:1 proton-atropine complex. Two main factors, pH and temperature, which have notable effects on the hydrolysis rate, are illustrated. The most suitable pH for atropine to be preserved in aqueous solution and related parameters were estimated.

ANODIC-OXIDATION OF HYDRAZINE ON GLASSY-CARBON MODIFIED BY MACROCYCLIC TRANSITION-METAL COMPLEXES .1. COBALT PROTOPORPHYRIN DIMETHYL ESTER MODIFIED ELECTRODE

The electrocatalytic oxidation of hydrazine (N2H4) on a glassy carbon electrode (GC) modified by monolayer and polymer films of cobalt protoporphyrin dimethyl ester (CoPP) has been studied. Both the monolayer and polymer films of CoPP are very active to the anodic oxidation of N2H4. The activity of CoPP for the anodic oxidation of N2H4 is dependent on the pH of the solution, and the thickness of polymerized CoPP film. The oxidation kinetics were examined by methods of cyclic voltammetry, rotating disc electrodes and steady-state polarization measurement.

羟基自由基降解琼胶及其产物的活性研究

琼胶是一种从石花菜等红藻中提取的，目前生产工艺和结构等方面研究比较成熟的海藻多糖，广泛应用于医药、仪器等行业。但是，海藻多糖因为具有分子量大，粘度大，溶解度较小的等特点，而使其应用范围受到限制。利用降解的手段对其进行修饰，降低分子量和粘度，改善溶解性，可以拓展其应用范围。并且根据文献报道，琼 胶寡糖具有一些特殊的生物活性，如抗氧化性，抗炎症等。因此，对琼胶降解的研究具有生要意义。本研究中，为了选择一种合适的降解方法，进行了几种水解方法的尝试，其中包括在不同湿度和酸度下盐酸水解，过氧化氢和醋酸催化水解，Fenton体系羟基自由基降解。对于酸水解和Fenton体系氧化还原降解方法，通过粘度法对反应的速度进行了比较，表明氧化还原降解反应中琼胶的粘度降低比较快，并且具有代表性和新意，确定为本实验的降解琼胶的方法并对氧化还原降解所得的产物进行了活性实验。通过模仿自然界普遍存在的氧化还原降解反应，利用Vc诱导的Fenton体系产生的羟基自由基氧化还原降解琼胶得到低分子量的琼胶。降解产物经过高速离心、60％乙醇沉淀，除去分子量比较大的降解产物和磷酸盐，得到可溶于60％乙醇的分子量估计小于3000的降争产物，其产率为85％。利用经Sephadex-G25凝胶色谱分离所香的不同分子量的级分进行分子量和α－葡萄糖苷酶抑制活性关系的实验。降解产物对α－葡萄糖苷酶的抑制率和各级分的浓度呈线性正相关，并且各级分的IC_(50)则随着分子量的降低而降低。另外，对所得的降解产物混合物进行了红外吸收光谱、质子去偶核磁共震碳谱和负离子基质辅助激光诱导－飞行时间质谱结构分析。结果表明，氧化还原降解反应的专一性差，在得到寡糖的同时，在光谱图中出现一些比较复杂的副产物的结构信息。最后，根据MTT法的原理，以有体皮肤成纤维细胞为材料，通过紫外线辐射产生自由基造成氧化损伤，研究降解产物对成纤维细胞的保护作用。当无紫外线辐射时，降解产物对成纤维细胞具有显著的促进生长增殖作用：当经UVa、UBb辐射时则可以显著地表现出对损伤的保护作用，并且这种促进生长和保护作用呈显著的量效关系，表明降解产物具有清除基自由基的作用。但是，因为氧化还原降解以应的机理尚不十分明的以及琼羟胶的特殊结构，使得反应的副产物很难预测，也就使得分离工作难以进行，所以，根据目前所得的信息，尚不能确定是降解产物的什么级分产生的以上两种生物活性。

Salt-assisted acid hydrolysis of chitosan to oligomers under microwave irradiation

The effect of inorganic salts such as sodium chloride on the hydrolysis of chitosan in a microwave field was investigated. While it is known that microwave heating is a convenient way to obtain a wide range of products of different molecular weights only by changing the reaction time and/or the radiation power, the addition of some inorganic salts was shown to effectively accelerate the degradation of chitosan under microwave irradiation. The molecular weight of the degraded chitosan obtained by microwave irradiation was considerably lower than that obtained by traditional heating. Moreover, the molecular weight of degraded chitosan obtained by microwave irradiation assisted under the conditions of added salt was considerably lower than that obtained by microwave irradiation without added salt. Furthermore, the effect of ionic strength of the added salts was not linked with the change of molecular weight. FTIR spectral analyses demonstrated that a significantly shorter time was required to obtain a satisfactory molecular weight by the microwave irradiation-assisted inorganic salt method than by microwave irradiation without inorganic salts and conventional technology. (C) 2005 Elsevier Ltd. All rights reserved.

Synthesis and quantum-chemistry analysis on novel triazole compounds containing ester group

Nine novel triazole compounds containing ester group were designed and synthesized. Their structures were confirmed by elemental, H-1 NMR and IR analyses, and optimized by means of DFT (Density Functional Theory) method at the B3LYP/6-31G* level. Based on the quantum-chemical calculation results and the Pearson coefficients between FA and quantumchemical parameters, V, LogP, MR and E-HOMO are shown to be the important relative factors which affect FA of the title compounds.

Salt-assisted acid hydrolysis of starch to D-glucose under microwave irradiation

The effect of inorganic salts on the hydrolysis of starch in a microwave field was investigated and it was found that some inorganic salts can effectively accelerate the acid hydrolysis of starch. The yield of D-glucose reached 111 wt% (equal to the theoretical yield). (C) 2001 Published by Elsevier Science Ltd. All rights reserved.

Damage of a High-Energy Solid Propellant and Its Deflagration-to-Detonation Transition

In order to assess the safety of high-energy solid propellants, the effects of damage on deflagration-to-detonation transition (DDT) in a nitrate ester plasticized polyether (NEPE) propellant, is investigated. A comparison of DDT in the original and impacted propellants was studied in steel tubes with synchronous optoelectronic triodes and strain gauges. The experimental results indicate that the microstructural damage in the propellant enhances its transition rate from deflagration to detonation and causes its danger increase. It is suggested that the mechanical properties of the propellant should be improved to restrain its damage so that the likelihood of DDT might be reduced.

Damage of a high-energy solid propellant and its effects on combustion

In order to improve the safety of high-energy solid propellants, a study is carried out for the effects of damage on the combustion of the NEPE (Nitrate Ester Plasticized Polyether) propellant. The study includes: (1) to introduce damage into the propellants by means of a large-scale drop-weight apparatus; (2) to observe microstructural variations of the propellant with a scanning electron microscope (SEM) and then to characterize the damage with density measurements; (3) to investigate thermal decomposition; (4) to carry out closed-bomb tests. The NEPE propellant can be considered as a viscoelastic material. The matrices of damaged samples axe severely degraded, but the particles are not. The results of the thermal decomposition and closed-bomb tests show that the microstructural damage in the propellant affects its decomposition and burn rate.