Pickering乳液聚合法制备复合防晒微球体

设计了一种表面负载物理防晒剂TiO2、内部包埋化学防晒剂阿伏苯宗(AVB)的PMMA微球体(TiO2@PMMA-AVB),并以TiO2纳米粒子为Pickering乳化剂,利用Pickering乳液聚合法,在无表面活性剂的条件下一步法制备了TiO2@PMMA-AVB复合防晒微球体.紫外光透过率、光稳定性、体外透皮以及感官...     

W/O微乳液技术与纳米粒子的控制合成

分析了W／O微乳液的形成机理、结构特征以及用W／O微乳液法合成纳米粒子的基本原理。讨论了制备条件如水与表面活性剂的比值,反应物、表面活性剂、助表面活性剂的浓度以及焙烧条件对纳米粒子特征的影响。指出应该加强对纳米粒子生成反应动力学的研究,加强微乳液法与其它纳米粒子制备技术的耦合研究,并注意改善非极性溶剂和表面活性剂的回收率以降低制备成本。     

苯乙烯无皂乳液聚合接枝纳米TiO2的研究

采用无皂乳液聚合法，使苯乙烯单体（St）在烷基化预处理的纳米TiO2粒子的表面进行接枝聚合，得到了稳定的以纳米TiO2粒子为核、接枝聚苯乙烯为壳的复合颗粒（TiO2-g-PS）。研究了烷基化预处理以及聚合条件（单体浓度、引发剂浓度、反应时间）对TiO2表面接枝改性的影响，并对其聚合机理进行了探讨。结果表明：PS以化学键成功地接到纳米TiO2的表面，并且可以通过改变接枝聚合的条件来调节粒子上所接聚苯乙烯的结构，为进一步优化纳米粒子填充聚合物复合材料的结构和性能之间的关系建立基础。     

纳米级TiO2粒子改性及其填充聚丙烯的研究

分别用油酸钠、氯化聚丙烯及甲基丙烯酸甲酯对纳米级TiO2粒子进行表面处理或表面接枝改性。通过熔融共混工艺制备了PP／纳米TiO2复合材料,并进行了力学测试和结构表征。结果表明,经过表面处理的纳米TiO2粒子可以较均匀地分散在聚丙烯中,粒子与基体界面结合良好,填充聚丙烯形成的复合材料的拉伸强度、冲击强度都有所提高。     

反胶束法纳米TiO_2的UV-vis和TEM研究

用石油醚为溶剂的反胶束体系溶胶-凝胶法合成了纳米TiO2,采用UV-vis光谱跟踪纳米TiO2粒子粒径的变化,研究了影响纳米TiO2溶胶粒子大小的因素,采用TEM表征了纳米TiO2的粒子大小及其粒径分布。结果表明,合成的反胶束纳米TiO2的UV-vis光谱吸收边λonset为344.8~363.2 nm,与锐钛型纳米TiO2的吸收边λonset=385 nm相比,紫外可见光谱发生“蓝移”,反胶束纳米TiO2粒子的半径为5~6.5 nm;TEM表明,纳米TiO2粒子的粒径为15~55 nm,粒径分布较窄,粒径分布指数SD I为1.19~1.29;FTIR谱图表明,TiO2粒子为表面具有一定数量钛羟基的水合TiO2。     

纳米TiO2作为润滑油添加剂的制备及结构表征

利用液相沉积法制备了十二烷基三甲氧基硅烷(DTMS)修饰的油溶性纳米TiO2粒子,研究了修饰温度、修饰时间和修饰剂用量对TiO2油溶性以及在基础油中分散稳定性的影响,并采用红外光谱仪(FT-IR)、透射电子显微镜(TEM)进行了结构表征。结果表明,修饰温度为40℃,修饰时间为12 h,修饰剂与TiO2的摩尔比为2∶1时,所得粒子具有最佳亲油化度和分散稳定性。结构表征表明,纳米TiO2粒子表面的DTMS修饰膜有效控制了粒径的过度增长,避免粒子间的团聚,增强了纳米TiO2在基础油中的分散稳定性。     

TiO2纳米粒子的制备及表征

利用溶胶-凝胶法制备了TiO2纳米粒子,并利用透射电子显微镜、扫描电子显微镜、紫外-可见吸收光谱仪和傅立叶转换红外光谱仪对TiO2纳米粒子的形貌、结构和尺寸进行了表征。结果表明:TiO2纳米粒子为近球形,粒径为12~15nm左右的锐钛矿型纳米晶;TiO2溶胶薄膜中粒子均匀分散,有较好的均一性;TiO2纳米粒子表面富氧,含有较多的TiOH基团;TiO2纳米粒子尺寸对反应体系的pH值很敏感;不同尺寸的纳米粒子在紫外区均有较强吸收,并表现出吸收带边蓝移效应。     

丙烯酸丁酯原位乳液接枝纳米TiO2的研究

为了提高纳米二氧化钛（TiO2）粒予在聚合物基复合材料中的分散性,需要对粒子的表面进行改性。实验采用无皂乳液聚合法,使丙烯酸丁酯单体（BA）在偶联剂KH-570烷基化预处理的纳米TiO2粒子的表面进行接枝聚合,研究了偶联剂用量对烷基化预处理程度的影响,以及聚合条件对TiO2表面接枝效果的影响,并对其聚合机理进行了探讨。结果表明,PBA以化学键成功地接到纳米TiO2的表面,并且可以通过改变接枝聚合条件来调节粒子上所接聚丙烯酸丁酯的结构,为进一步优化纳米粒子填充聚合物复合材料的结构和性能之间的关系建立基础。     

利用工业钛液制备纳米二氧化钛

本文以工业钛液及尿素为原料,采用均匀沉淀法制备出高纯的球状单分散纳米TiO2超细粉。考察了制备工艺流程中的主要影响因素硫酸氧钛浓度、尿素配比、反应温度、表面活性剂等对粒径的影响,并利用TEM、XRD等手段对颗粒进行表征,得出了最佳制备条件。将前驱体微波干燥10min,在550℃下煅烧1h,得到平均粒径为26nm的锐钛矿型纳米二氧化钛。     

原位聚合法表面改性TiO2研究

用阴离子表面活性剂十二烷基苯磺酸钠(LAS)处理TiO2粉体,后以原位聚合的方法得到了TiO2的无机有机复合粒子,并对复合粒子进行了必要的表征,探索了复合粒子的形成机理,研究了聚合条件对复合粒子形成过程的影响。结果表明TiO2复合粒子的表面性质已由亲水转变为亲油,可以认为表面包覆了St-BA共聚物的TiO2复合粒子。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.