L-丙交酯的制备与聚合研究

首先以L-乳酸为原料，合成了L-丙交酯。考察了解聚温度对L-丙交酯产率的影响。结果表明，当解聚温度超过235℃时，丙交酯的构型发生变化，所得产物为现．丙交酯；然后以辛酸亚锡为催化剂，以开环聚合的方法合成了聚L-乳酸，研究了催化剂的用量、聚合时间、聚合温度对聚L-乳酸摩尔质量的影响。     

2-乙基己酸亚锡催化合成丙交酯的合成工艺研究

丙交酯是以乳酸为原料制备高分子量聚乳酸的中间体。研究以2-乙基己酸亚锡为催化剂,以D,L-乳酸为原料,在催化剂存在下通过脱水环化合成D,L-丙交酯。研究了催化剂用量、脱水时间、解聚温度对丙交酯产率的影响。实验结果表明,采用2-乙基己酸亚锡为催化剂,最佳催化剂用量为1.3%,最佳脱水温度为140℃,最佳解聚时间为90 min。用乙醇作为重结晶溶剂,可获得总产率达25.3%的纯D,L-丙交酯。通过熔点、红外光谱(IR)对产品进行了表征。     

低真空条件下D,L-丙交酯的合成研究

为了提高D,L-丙交酯的收率,研究了D,L-乳酸为单体,低真空条件下使乳酸单体先缩聚后解聚制备D,L-丙交酯的工艺条件。考察了制备过程中脱水温度、脱水率、催化剂量、聚合温度和解聚温度对丙交酯产率的影响。结果表明,以ZnO为催化剂,用量为1.2%,在全程低真空条件下,乳酸分别在120~160℃脱水和220~250℃解聚,以无水乙醇和乙酸乙酯作为溶剂改进了粗产品的提纯方法,可得到产率达40.2%的丙交酯。毛细管熔点法测定了产物的熔点,并用红外光谱、差示扫描量热法、X-射线衍射分析对产物进行了分析表征。所得产物为高纯的环状丙交酯。     

有机锡化合物引发D,L-丙交酯的开环聚合

D,L-丙交酯在有机锡化合物四苯基锡(Ph4Sn)、三正丁基醋酸锡(Bu3SnOAc)、辛酸亚锡(SnOct2)等催化剂引发下开环聚合,得到高分子量的聚D,L-乳酸,讨论了聚合单体D,L-丙交酯纯度、聚合温度、聚合时间、聚合体系真空度以及引发剂有机锡催化剂与聚合单体D,L-丙交酯的比例对聚D,L-乳酸合成的影响,通过红外光谱和核磁共振光谱对聚D,L-乳酸的结构进行了表征。实验结果表明,D,L-丙交酯开环聚合反应的较佳工艺路线是:D,L-丙交酯重结晶5次,聚合温度140℃,聚合时间24 h,聚合体系真空度13.3~133.3 Pa,引发剂有机锡催化剂与单体D,L-丙交酯比例0.2‰~0.5‰,此时聚D,L-乳酸的粘均分子量最高,分别达到32.46×104,33.43×104和41.36×104。     

L-丙交酯的合成及其纯化条件优化研究

以L-乳酸为原料、辛酸亚锡为催化剂,经缩聚和解聚两步反应合成了L-丙交酯,研究了催化剂用量、脱水温度、解聚温度等因素对L-丙交酯产率及纯度的影响.利用改进的合成工艺得到粗L-丙交酯,然后采用浓度梯度与交替溶剂相结合的方法进行重结晶,使精制L-丙交酯的总产率和纯度同时得到了提高.通过熔点、比旋光度、红外光谱、核磁共振氢谱等对产物L-丙交酯进行了表征.     

离子液体催化合成丙交酯

丙交酯是合成可降解材料聚乳酸的重要中间体。以D、L-乳酸为原料，在离子液体催化剂存在下脱水环化合成丙交酯，研究了反应过程中离子液体的种类及用量等因素对丙交酯产率的影响，粗产品经重结晶纯化得到高纯度D、L-丙交酯，通过熔点、红外光谱和紫外光谱对产品进行了表征；实验表明，以离子液体为催化剂制备丙交酯具有可行性，体系粘度降低，反应条件温和，有利于丙交酯的生成；确定了[NH(C₂H₅)₃][HSO₄]为催化剂时的适宜工艺条件为催化剂用量5 wt%，缩聚温度110～140℃，解聚温度190～250℃。     

聚乳酸中间体——丙交酯制备工艺

研究了间接法合成聚乳酸用的中间体丙交酯的制备工艺。以工业D,L-乳酸(lacticacid)为原料,丙交酯粗产物的收率为考查指标,通过正交实验得到了最佳制备工艺条件为:以4%(v/v)的辛酸亚锡为催化剂,脱水温度为180℃,解聚温度为285℃,得到粗产物收率为72.4%。粗品丙交酯1次重结晶后收率为59.3%,熔点为95.0～96.2℃;5次重结晶后总收率为50.7%,熔点为125.2～126.5℃。同时采用FTIR与1HNMR对产物进行了结构表征。     

ε-己内酯均聚物及共聚物的合成与表征

分别以D,L-乳酸和L-乳酸为原料制得D,L-丙交酯(D,L-LA)和L-丙交酯(L-LA);以辛酸亚锡为内酯开环聚合引发剂,用ε-己内酯(ε-CL)开环均聚合制备聚ε-己内酯,考察了引发剂用量、聚合时间和温度等对聚合产物特性黏数的影响。由ε-CL与D,L-LA和L-LA共聚合制得聚(ε-己内酯-D,L-丙交酯)和聚(ε-己内酯-L-丙交酯),并用傅里叶变换红外光谱、核磁共振氢谱、差示扫描量热法、X射线衍射等对聚合物的结构进行表征;力学性能测试结果表明,聚(ε-己内酯-L-丙交酯)具有很好的弹性和较高的断裂伸长率。     

开环聚合法合成聚乳酸的研究

采用D,L-乳酸为原料,在丙交酯合成工艺中,以ZnO/Sn(Oct)2为催化剂,用量为反应物总质量的2.0%,同时采用减压气流法,能使丙交酯的收率高达39.2%;在丙交酯开环聚合工艺中,反应温度为160℃,制备出聚乳酸的分子量达到8.9×104。使用微机熔点仪、红外光谱(IR)分别对丙交酯的纯度与聚乳酸的结构进行了表征。     

丙交酯制备过程中几种影响因素的研究

以L-乳酸为原料在催化剂存在的条件下,加热脱水、裂解合成了L-丙交酯。研究了脱水温度、脱水时间、裂化反应温度及催化剂种类对丙交酯产率的影响。通过正交实验确定的最优反应条件为:脱水温度120℃、脱水时间4h、裂化温度240℃、催化剂为辛酸亚锡,并通过工艺的改进,大幅提高了丙交酯的产率,达到56.9%。     

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.     

Sapindaceae,cyanolipids, and bugs

Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA.     

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.     

2008～2009年世界塑料工业进展

收集了2008年7月～2009年6月世界塑料工业的相关资料,介绍了2008～2009年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、环氧树脂、不饱和聚酯树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍。     

ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究

建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。