苯乙烯分散聚合工艺条件对转化率及微球尺寸的影响

以乙醇／水混合液为分散介质，聚乙烯基吡咯烷酮为稳定剂，研究了苯乙烯分散聚合过程中引发剂浓度，单体浓度及分散稳定剂用量对转化率和微球粒径及粒径分布的影响。实验表明，通过反应中期补加引发剂，后期升温的方法，可使聚合反应的转化率达到90％以上，微球粒径增大，粒度均匀。     

胺基双酚钴在合成极性单体与苯乙烯嵌段共聚物中的应用

采用低成本、高活性胺基-双酚钴配合物调控的自由基聚合(CMRP)和催化链转移反应(CCT)对乙酸乙烯酯或丙烯酸叔丁酯与苯乙烯单体进行了共聚反应。以钴配合物为催化剂、偶氮二异丁腈(AIBN)为引发剂、聚乙烯吡咯烷酮(PVP)为分散剂,通过溶液聚合方法得到的聚乙酸乙烯酯和聚丙烯酸叔丁酯作为大分子引发剂,引发苯乙烯的分散聚合,从而获得具有较低分子量分布(～1.93)的丙烯酸叔丁酯和苯乙烯的共聚物及乙酸乙烯酯和苯乙烯的共聚物(PVAc-b-PS和PtBA-b-PS),数均分子量随单体转化率线性增加。运用凝胶渗透色谱、核磁共振波谱、扫描电子显微镜等测试手段对合成的嵌段共聚物进行了表征。     

基于均匀设计的苯乙烯分散聚合反应研究

本文基于均匀设计方法对苯乙烯的分散聚合反应进行了试验设计,并通过回归分析,建立了聚苯乙烯粒子相关性能参数(聚苯乙烯粒子分子量、粒径大小及分布)和各变量(单体浓度、稳定剂用量、引发剂用量和反应介质溶度参数)之间的回归方程。根据回归方程进行了分散聚合反应的配方优化,得到了约束条件下的苯乙烯分散聚合反应配方,实测值与预测值比较结果表明,回归方程的预测值与优化配方制备的PS粒子的各项性能实测值存在一定的偏差(相对偏差在15%以内),但仍对试验配方设计有一定的指导作用。     

油酸/苯乙烯共聚乳液研究

本文以生物质产品油酸(OA)及苯乙烯(ST)为单体,以SDS为乳化剂,APS为引发剂,在N2环境下进行共聚反应,形成油酸/苯乙烯共聚乳液。考查了聚合工艺、引发剂用量、反应温度以及单体配比等因素对单体转化率的影响。研究表明:采用半连续预乳液聚合工艺,单体配比为2:1时,反应温度控制在90℃时可制得转化率相对较高、聚合稳定性好的共聚乳液。     

非极性混合介质中分散聚合法制备聚乙烯基吡咯烷酮

以乙烯基吡咯烷酮(NVP)为单体,环己烷的混合溶剂为分散介质,AIBN为引发剂,SEBS为分散剂,采用分散聚合的方法制备了分散性能好、粒径为1μm左右、热稳定性较好的聚乙烯基吡咯烷酮。考察了单体含量、引发剂用量、分散剂用量对分散聚合反应的影响。结果表明,转化率和分子量均随单体含量增加而增大,随引发剂的量的增大而减小;且在单体含量为30%、AIBN的用量为0.5%,分散剂用量为10%时,所合成的聚合物分子量最大。     

乳液法聚苯乙烯纳米微球的制备

采用十二烷基硫酸钠为乳化剂、过硫酸盐为引发剂、苯乙烯为单体,在低水油比的条件下,采用乳液聚合方法合成了聚苯乙烯纳米微球,探讨了乳化剂用量、乳化时间、反应温度、引发剂用量和反应时间对单体转化率及产物分子量的影响.结果表明:在低水油比条件下,反应参数对苯乙烯的转化率和聚苯乙烯的分子量具有一定的影响.在最优条件下苯乙烯的转化率达到98%、聚苯乙烯的分子量达到32万.激光粒度分布测试结果显示,所得产物为单分散纳米微球.     

异丙醇-水介质中微米级单分散聚(苯乙烯-甲基丙烯酸)微球的制备

以苯乙烯和甲基丙烯酸为单体、PVP为分散剂,AIBN为引发剂,在异丙醇-水介质中,用分散聚合方法制备了微米级单分散的聚(苯乙烯-甲基丙烯酸)[P(St-MAA)]微球。结果表明,采用反应初期低温、中后期升温的聚合工艺可制得单分散的聚合物微球,并提高聚合反应的速率和转化率。P(St-MAA)微球的粒径及其分布可通过改变介质组成来控制。分散介质中异丙醇质量分数降低,聚合反应速率增大,转化率升高,微球的粒径减小。当分散介质中异丙醇的质量分数降低到60％时,聚合反应中有凝胶生成,粒径分布呈多分散性。     

阴离子聚合(Ⅳ)

3.5.共聚反应 3.5.1.无规共聚 丁二烯和苯乙烯单体在烃类溶剂中,用丁基锂引发,很容易进行共聚反应。分析不同转化率的共聚物组成,发现在反应前期,只有很少量的苯乙烯参与共聚反应,其反应速度几乎是丁二烯自聚速度进行。苯乙烯单     

乳聚丁苯橡胶中苯乙烯结合量与单体转化率的Monte Carlo模拟

在乳聚丁苯橡胶的标准单体配方条件下,采用Monte Carlo方法对在体积为10-20m3的微型反应器中只产生1个自由基生成1条链的链增长过程进行了模拟。结果表明,在某一单体转化率下,聚合物中苯乙烯的瞬时结合量是不确定的,但是大致在某一范围内变动,总体趋势是在反应初期随单体转化率升高基本不变,而后随单体转化率的升高而增加,越到反应后期随单体转化率上升而增加得越快;随单体转化率升高,平均结合苯乙烯量上升。在乳聚丁苯橡胶合成过程中的单体转化率介于38%～74%,所合成丁苯橡胶的平均结合苯乙烯质量分数为22.5%～24.5%,符合国家标准的要求。     

水包水聚丙烯酸乳液的合成研究

文章以丙烯酸、丙烯酰胺、甲基丙烯酸为单体,采用分散聚合方式合成了聚丙烯酸共聚物,反应以盐水溶液为介质,在稳定剂及其它助剂的作用下,得到的聚合物为水包水的聚合物乳液,平均粒径为几百微米。研究了引发剂、反应时间、盐的用量等对聚合物特性粘数、单体转化率及产物稳定性的影响。     

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.     

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。     

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.     

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.     

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.