Phase behavior, rheological property, and transmutation of vesicles in fluorocarbon and hydrocarbon surfactant mixtures

We present a detailed study of a salt-free cationic/anionic (catanionic) surfactant system where a strongly alkaline cationic surfactant (tetradecyltrimethylammonium hydroxide, TTAOH) was mixed with a single-chain fluorocarbon acid (nonadecafluorodecanoic acid, NFDA) and a hyperbranched hydrocarbon acid [di-(2-ethylhexyl)phosphoric acid, DEHPA] in water. Typically the concentration of TTAOH is fixed while the total concentration and mixing molar ratio of NFDA and DEHPA is varied. In the absence of DEHPA and at a TTAOH concentration of 80 mmol·L(-1), an isotropic L(1) phase, an L(1)/L(α) two-phase region, and a single L(α) phase were observed successively with increasing mixing molar ratio of NFDA to TTAOH (n(NFDA)/n(TTAOH)). In the NFDA-rich region (n(NFDA)/n(TTAOH) > 1), a small amount of excess NFDA can be solubilized into the L(α) phase while a large excess of NFDA eventually leads to phase separation. When NFDA is replaced gradually by DEHPA, the mixed system of TTAOH/NFDA/DEHPA/H(2)O follows the same phase sequence as that of the TTAOH/NFDA/H(2)O system and the phase boundaries remain almost unchanged. However, the viscoelasticity of the samples in the single L(α) phase region becomes higher at the same total surfactant concentration as characterized by rheological measurements. Cryo-transmission electron microscopic (cryo-TEM) observations revealed a microstructural evolution from unilamellar vesicles to multilamellar ones and finally to gaint onions. The size of the vesicle and number of lamella can be controlled by adjusting the molar ratio of NFDA to DEHPA. The dynamic properties of the vesicular solutions have also been investigated. It is found that the yield stress and the storage modulus are time-dependent after a static mixing process between the two different types of vesicle solutions, indicating the occurrence of a dynamic fusion between the two types of vesicles. The microenvironmental changes induced by aggregate transitions were probed by (19)F NMR as well as (31)P NMR measurements. Upon replacement of NFDA by DEHPA, the signal from the (19)F atoms adjacent to the hydrophilic headgroup disappears and that from the (19)F atoms on the main chain becomes sharper. This could be interpreted as an increase of microfluidity in the mixed vesicle bilayers at higher content of DEHPA, whose alkyl chains are expected to have a lower chain melting point. Our results provide basic knowledge on vesicle formation and their structural evolution in salt-free catanionic surfactant systems containing mixed ion pairs, which may contribute to a deeper understanding of the rules governing the formation and properties of surfactant self-assembly.     

聚合物胶束结合靶向在肿瘤化疗中的研究进展

肿瘤研究的一个主要方向是开发高效无毒副作用的药物载体系统。聚合物胶束由内部可装载难溶性药物的疏水内核,外部能提高体内运输作用的亲水外壳组成,粒径一般为10～100nm左右。这种粒径范围的载药体系既能逃脱肾脏的排泄清除,又能躲避内皮网状系统的吞噬,延长药物在血液中的循环时间。聚合物胶束结合肿瘤靶向在化疗方面的应用,能够有效改善化疗药物的水溶性,提高化疗药物的利用率和抗肿瘤活性,降低对机体正常细胞组织的毒副作用,克服多药耐药性问题,进而极大地提高了肿瘤化疗效果和促进了肿瘤化疗的发展进步。本文着重综述聚合物胶束在化疗药物载药与靶向策略方面的研究现状与进展。     

研究简报聚苯乙烯接枝TiO2有机无机杂化超疏水涂层的制备

采用自由基聚合的方法,在经乙烯基三乙氧基硅烷(VTEOS)修饰的纳米TiO2表面上接枝聚苯乙烯(PS),而后制得PS-g-TiO2有机无机纳米杂化超疏水薄膜。利用场发射扫描电子显微镜和傅里叶变换红外光谱仪对PS-g-TiO2进行了形貌和结构表征,并探讨了VTEOS修饰对TiO2纳米粉体表面浸润性能的影响。测试结果表明,纳米TiO2经VTEOS改性后所制备的PS-g-TiO2薄膜和仅用硅烷偶联剂修饰的TiO2薄膜都具有良好的超疏水性能,水滴在薄膜上的最大静态接触角分别为160°和154°,滑动角分别为3°和4°。     

The amount effect of catalyst on the urethane reaction of o-hydroxybenzyl alcohol

The urethane reaction of o-hydroxybenzyl alcohol with phenyl isocyanate was monitored with in situ FT-IR.Dibutyltin dilaurate was used as catalyst and its amount effect was investigated.It was found that there was an obvious induction period before reaction began.It was interesting that the time of induction period climbed up and then declined with the increase of dibutyltin dilaurate. When the concentration of dibutyltin dilaurate reached 9.58×10^-5 mol/L,the induction period disappeared completely and hereafter did not appear any more.Furthermore,the urethane reaction kinetics was studied.When the concentration of dibutyltin dilaurate increased,the reaction rate of phenolic group（k₁） increased sharply,but the reaction rate of alcoholic group（k₂） appeared of little change on the whole.k₁ increased about 20-fold,yet k₂ increased about 2-fold when the concentration of dibutyltin dilaurate varied from 9.58×10^-6 mol/L to 1.92×10⁴ mol/L,which made the value of k₁/k₂ enlarge.     

Production of high-quality agarwood in Aquilaria sinensis trees via whole-tree agarwood-induction technology

We used whole-tree agarwood-induction technology to produce agarwood from Aquilaria sinensis trees within 20 months,and evaluated the quality of this agarwood.The results showed its characteristics were similar to those of high-grade wild agarwood in terms of texture,chemical constituents,essential oil content,and ethanol-soluble extract content,with the lattermost quality far surpassing the requirement of traditional Chinese medicine agarwood,as indicated in Chinese Pharmacopoeia 2010.To the best of our knowledge,this is first study to show that high-quality agarwood can be produced in whole A.sinensis trees via a chemically induced technology.     

一种Gemini表面活性剂合成及其在薄膜中的应用

通过硬脂酸乙酯、甲酸乙酯、1,2-二溴乙烷、无水乙醇、金属钠、二聚甘油等原料合成非离子Gemini表面活性剂-Gemini硬脂酸二聚甘油酯(PGGE)。利用红外光谱、核磁共振氢谱对其进行了结构表征。测试了其性能,并与单硬脂酸二聚甘油酯(PGME)进行了比较。结果表明,该PGGE表面活性剂γcmc为31.1 mN.m-1,cmc为0.0039 mmol.L-1。将其用在农用塑料薄膜上,考察了其防雾滴性能,应用实验表明,该表面活性剂是一种性能优良的塑料薄膜防雾滴剂。     

Photoluminescence of Nanoporous GaN Films Prepared by Electrochemical Etching

Nanoporous （NP） CaN is prepared by electrochemical etching on a CaN epilayer grown on a sapphire substrate by metal-organic chemical vapor deposition. Scanning electron microscopy reveals that the average pore diameter and inter-pore spacing are approximately 25 and 45 nm, respectively. The photoluminescence （PL） spectra show that in contrast to the initial as-grown CaN epilayer, the NP CaN exhibits a high near-band-edge UV intensity, significant relaxation of compressive strain, and a lower yellow luminescence intensity. Both the line shape and line width of the PL spectra are almost the same for these two samples. The high quality of the NP CaN can be explained by the enhancement of the PL extraction efficiency and the decrease of impurity and defect density after etching.     

Preparation of hollow silica nanospheres in O/W microemulsion system by hydrothermal temperature changes

Hollow silica nanospheres with wrinkled or smooth surfaces were successfully fabricated through a hydrothermal method. In this method, oil-in-water microemulsion (composed of cyclohexane, water, ethanol, and cetyltrimethylammonium bromide), and polyvinylpyrrolidone were utilized as template and capping agent, respectively. In such a facile synthesis, we can well realize the morphological transformation of spheres with radially oriented mesochannels to hollow structures of silica nanoparticle only by regulating the hydrothermal temperature from 100 °C to 200 °C. Synthesized samples with different mesostructures were then used as supports to immobilize Candida rugosa lipase (CRL). The immobilized CRL was employed as a new biocatalyst for biodiesel production through the esterification of heptanoic acid with ethanol. The conversion ratio of heptanoic acid with ethanol catalyzed by the immobilized CRL was also evaluated. Results of this study suggest that the prepared samples have potential applications in biocatalysis.     

Theoretical studies on the mechanism of chlorination reaction of trichlorogermyl acrylic acid

The mechanism of the chlorination reaction of trichlorogermyl acrylic acid has been studied systematically using quantum chemistry methods. Geometries of reactants, transition states and products have been optimized at the B3LYP/6-311G(d,p) level. Vibrational frequencies, IR intensities and relative energies for various stationary points have been determined. The reaction pathways have been identified by intrinsic reaction coordinate (IRC) calculations. Theoretical analysis provides conclusive evidence that the process proceeds through two and three pathways for the first and second reaction steps, respectively.     

Design of Energetic Materials Based on Asymmetric Oxadiazole

A new family of asymmetric oxadiazole based energetic compounds were designed. Their electronic structures, heats of formation, detonation properties and stabilities were investigated by density functional theory. The results show that all the designed compounds have high positive heats of formation ranging from 115.4 to 2122.2 kJ mol⁻¹. −N− bridge/−N₃ groups played an important role in improving heats of formation while −O− bridge/−NF₂ group made more contributions to the densities of the designed compounds. Detonation properties show that some compounds have equal or higher detonation velocities than RDX, while some other have higher detonation pressures than RDX. All the designed compounds have better impact sensitivities than those of RDX and HMX and meet the criterion of thermal stability. Finally, some of the compounds were screened as the candidates of high energy density compounds with superior detonation properties and stabilities to that of HMX and their electronic properties were investigated.