利用单分子层气——液界面特性研究氯化二—（十八烷基）二甲铵的物理化学特性

在不同温度不同盐浓度的液－气界面上，测得了氯化二－（十八烷基）二甲铵（ＤＯＤＡＣ）的等温线，通过研究表面电势证实了静电斥力在电离的亲水集团之间起着重要的作用。特别是在气液固的过渡阶段这一作用尤为显著。凝聚态下ＤＯＤＡＣ分子所占面积约为０．５８ｎｍ＾２，与用Ｘ光衍射所得结果相符。当用Ｌ－Ｂ技术将ＤＯＤＡＣ单分子层镀到金属表面后，扫描电势仪显示薄膜非常相符。

季铵盐DMADDM抗菌改性牙科材料的研究进展

口腔微生物导致的口腔微生态失衡,可诱发多种口腔感染性疾病:如龋病、牙周病、口腔念珠菌病、种植体周围炎等。因此,牙科材料的抗菌改性有利于口腔菌斑性疾病的防治。甲基丙烯酸十二烷基二甲铵(dimethylaminododecyl methacrylate,DMADDM)是一种季铵盐型抗菌单体,具有广谱抗菌活性。其结构中的甲基丙烯酰基团能够通过聚合反应和材料基质交联,形成非释放型长效抗菌材料。本文将对近年来DMADDM改性牙科材料的抗菌作用、抗菌机制和耐药性研究等方面作一综述。

新型抗菌性牙本质粘接剂抗菌性和粘接性能的研究

目的:研究甲基丙烯酸十二烷基二甲铵(dimethylaminododecyl methacrylate,DMADDM)对牙本质粘接系统的粘接强度和菌斑生物膜的影响。方法:合成DMADDM,并以质量分数为10%的比例添加到商品化的牙本质粘接剂中作为实验组,商品化的牙本质粘接剂作为对照组。使用人唾液培养所得到牙菌斑全菌生物膜模型来研究粘接剂的抗菌性,检测死/活细菌染色;检测蒸馏水和口腔全菌生物膜培养14 d前后,实验组和对照组粘接强度的差异。结果:添加DMADDM的粘接系统显著降低了菌斑生物膜活性;蒸馏水浸泡14 d对粘接强度没有明显影响(P>0.05),菌斑生物膜浸泡14 d后,对照组粘接强度明显下降(P<0.05),实验组没有明显变化(P>0.05)。结论:含有DMADDM的牙本质粘接系统具有很强的抗菌性,能够抵抗口腔环境对粘接性能的影响,具有一定的临床应用前景。

利奈唑胺中间体(S)-N-(2-乙酰氧基-3-氯丙基)乙酰胺合成工艺优化

S-环氧氯丙烷与氨水和苯甲醛反应,酸性水解后,4-二甲氨基吡啶作为催化剂,醋酐作为酰化试剂合成(S)-N-(2-乙酰氧基-3-氯丙基)乙酰胺。用LC-MS分析S-环氧氯丙烷与氨水反应的副产物,发现在氨水中加入醋酸铵可以抑制副反应,提高1-氨基-3-氯-2-丙醇的收率;在4-二甲氨基吡啶催化下与乙酸酐反应得到(S)-N-(2-乙酰氧基-3-氯丙基)乙酰胺,收率90.91%,时间缩短了4h。

FTIR analysis of adsorption of poly diallyl-dimethyl-ammonium chloride on kaolinite

The flocculation behavior of ultrafine kaolinite suspension was investigated through settlement tests and FTIR method was employed to probe the adsorption mechanism of flocculant on kaolinite. The results show that the maximum settling rate of kaolinite occurs at pH value of 3.33,which is close to the point of zero charge(PZC) of kaolinite (3.5). This result is in good agreement with the double electric layer theory. Kaolinite suspension reaches the largest settling rate at a low concentration of 39 g/t for poly diallyl-dimethyl-ammonium chloride(PDADMA) flocculant,whereas for polyacrylamides(PAM) the dosage is required to be 500 g/t. When macromolecule polymer is adsorbed on surface,kaolinite particles may be flocculant due to the bridging effect. There are cation flocculant characteristic bands on the spectrum of kaolinite but no obvious shifting. Thus,the adsorption of poly diallyl-dimethyl-ammonium chloride on kaolinite surface is physical adsorption.

Mechanism of separating muscovite and quartz by flotation

Flotation experiments were performed to investigate the separation of muscovite and quartz in the presence of dodecylamine(DDA), tallow amine(TTA) and dodecyltrimethylammonium bromide(DTAC). The adsorption mechanisms of these three kinds of amines on muscovite and quartz were studied by FT-IR spectrum analysis, contact angle measurement and molecular dynamics(MD) simulation. The results reveal that the separation of muscovite from quartz is feasible at strong acid pulp condition using amine collectors. TTA and DTAC show poorer collecting ability for flotation of the two minerals compared with DDA. Physical adsorption is found to be the main adsorption module of amine collectors on muscovite and quartz by FT-IR analysis. MD simulation results show a strong physical adsorption ability of DDA+ cation on muscovite and quartz(muscovite(001):-117.31 kJ/mol, quartz(100):-89.43 kJ/mol), while neutral DDA molecular can hardly absorb onto the surface of these two minerals. These findings provide a novel explanation for the flotation mechanism from the perspective of MD simulation.

Repeated-batch Cultivation of Encapsulated Monascus purpureus by Polyelectrolyte Complex for Natural Pigment Production

In general,productions of natural pigment in submerged microorganism culture were much less than that in solid-state fermentation,because the solid-state culture can provide a support carrier for the mycelium. To improve natural pigment production,the cultivation of Monascus purpureus in submerged encapsulated cell was investigated. Monascus purpureus immobilized in polyelectrolyte complex(PEC) microcapsules,which were pre-pared by sodium cellulose sulphate(NaCS) and poly-dimethyl-diallyl-ammonium chloride(PDMDAAC),was a good substitute for submerged cell culture because it mimicked the solid-state environment. The repeated-batch process with encapsulated cells was studied in flasks and a bubble column. The results indicated that the bubble column was more suitable for the encapsulation culture than the shaking flasks because of its good mass transfer performance and minor shear stress on cells. Owing to the protection of the microcapsule's membrane,Monascus purpureus in microcapsules increased approximately three times over that in free cell culture with negligible cell leakage to the medium. The pigment production in the bubble column finally reached 3.82(OD500) ,which was two times higher than in free cell culture. In addition,the duration of each batch was shortened to 15% of that in free cell culture.

Kinetic Rate Constant of Liquid Drainage from Colloidal Gas Aphrons

A kinetic model fitted by the empirical equation has been proposed to describe the liquid drainage behavior. Rate constants （kd） of liquid drainage equation could be obtained from the above empirical equation. In this paper, the stability of the colloidal gas aphrons （CGAs）, the effect of concentrations of sodium dodecyl benzene sulphate （SDBS）, dodecyl trimethylammonium bromide （HTAB） and polyoxyethylene sorbitol anhydride monolaurate（Tween-20）, temperature, stirring speed, stirring time, and various kinds of salts on the kd of liquid drainage are further investigated. The results show that the Arrhenius equation can be successfully used to describe the relation between kd arid absolute temperature （T）, and concentrations of surfactants, stirring speed, stirring time and salinities also have great effect on the kd. At last, the CGAs drainage mechanism is explained from analysis of the rate of liquid drainage as a function of time.

Preparation of composite abrasives by electrostatic self-assembly method and its polishing properties in Cu CMP

The adsorption characteristics of cationic polyelectrolyte poly dimethyl diallyl ammonium chloride （PDADMAC） and anionic polyelectrolyte poly （sodium-p-styrenesulfonate） （PSS） on benzoguanamine formal- dehyde （BGF） particles are investigated. The charging characteristics of BGF particles are changed and con- trolled using electrostatic self-assembly method. A variety of PE,-BGF/SiO2 composite abrasives are obtained. The as-prepared samples are analyzed by zeta potential analysis, transmission electron microscope （TEM） and thermogravimetric （TG） analysis. The composite abrasive slurries are prepared for copper polishing. The poli- shing results indicate that it is SiO2 abrasives, not only coated SiO2 abrasive on polymer particles but also free SiO2 abrasive in slurry, that offer the polishing action. The material removal rates of copper polishing are 264 nm/min, 348 nm/min and 476 nm/min using single SiO2 abrasive slurry, PE0-BGF/SiO2 mixed abrasive slur- ry and PE3-BGF/SiO2 composite abrasive slurry, respectively. The surface roughness Ra of copper wafer （with 5μm×5μm district） is decreased from 0.166 μm to 3.7 nm, 2.6 nm and 1.5 nm, and the surface peak-valley values Rrv are less than 20 nm, 14 nm and 10 nm using these kinds of slurries, respectively. Key words ： chemico-mechanical polishing; polishing slurry; composite abrasives ; polyelectrolyte ; copper

Synthesis and High Electrocatalytic Performance of Hexagram Shaped Gold Particles Having an Open Surface Structure with Kinks

Hexagram shaped gold particles and their analogues enclosed by high index facets with kinks have been successfully synthesized by reducing HAuCl4 with ascorbic acid （AA） in the presence of poly（diallyldimethylammonium chloride） at room temperature. By using electron microscopy, the surfaces of the hexagram shaped Au particle were found to be {541} planes, which contain high-density steps and kinks. In addition, it was found that hexagonal shield-like and other kind of particles present in the product were analogues of the hexagram shaped Au particles structure, in that they had the same surface structure. In order to confirm the surface structure of all the prepared particles, surface structure sensitive underpotential deposition of Pb was carried out, and the cyclic voltammetric profile was in accordance with the proposed {541} surface. Finally, structure-property relationships of the Au hexagrams were experimentally analyzed by employing the electrocatalytic oxidation of AA as a probe reaction. The electrocatalytic reactions of gold cubes with low-index {100} facets and gold trioctahedra with {221} facets were studied as references. The experimental results showed that the hexagram shaped Au particles and their analogues with exposed {541} facets have the highest catalytic activity among the three kinds of gold particles, owing to the high density of kink atoms. This study should motivate us to further explore methods for the preparation of other well-defined polyhedral metal nanocrystals enclosed by high index surfaces.

Complexation of DNA with cationic surfactants as studied by small-angle X-ray scattering

The phase behaviors of the complex formed by didodecyldimethylammonium bromide（DDAB）and cetyltrimethylammonium bromide（CTAB）interacting with three different types of DNAs,salmon testes DNA（~2000 bp）,21-bp double-stranded oligonucleotides（oligo-ds DNA）,and 21-nt single-stranded oligonucleotides（oligo-ss DNA）were studied by synchrotron small-angle X-ray scattering.It was found that the DNA length and flexibility,together with the positive/negative charge ratio,determined the final structure.At higher charge ratios,the DNA length exhibited negligible effect.Both oligo-ds DNA and salmon DNA formed inverted hexagonal packing of cylinders with CTAB,as well as bilayered lamella with DDAB.However,at lower charge ratios,oligo-ds DNA formed a distorted hexagonal phase with CTAB and a new structure with DDAB,which was different from the behaviors of salmon DNA.The flexible oligo-ss DNA formed rich structures that were subject to environmental disturbance.Kinetic study also indicated that the structures of the complex formed by oligo-ss DNA took much longer to mature than the structures formed by oligo-ds DNA.We attributed this result to the conformational adjustment of oligo-ss DNA in the complex.

Synthesis of dimethyl adipate from cyclopentanone and dimethyl carbonate over solid base catalysts

A facile route for the synthesis of dimethyl adipate （DAP） from cyclopentanone and dimethyl carbonate （DMC） in the pres- ence of solid base catalysts has been developed. It was found that the intermediate carbomethoxycyclopentanone （CMCP） was produced from cyclopentanone with DMC in the first step, and then CMCP was further converted to DAP by reacting with a methoxide group. The role of the basic catalysts can be mainly ascribed to the activation of cyclopentanone via the abstraction of a proton in the a-position by base sites, and solid bases with moderate strength, such as MgO, favor the formation of DAP.