基于金纳米粒子团聚机理快速比色测定甲基硫菌灵

[目的]基于金纳米粒子(gold nanoparticle,AuNPs)的团聚机理,建立一种直接、快速、可视化的甲基硫菌灵农药检测方法.[方法]在酸性条件下,甲基硫菌灵分子上的=O键和=S键质子化,形成-OH和-SH,甲基硫菌灵通过Au-S键连接到AuNPs表面,再通过分子间的氢键相互作用,使甲基硫菌灵分子间相互连接,...     

甲基磺酸盐镀锡添加剂研究进展

综述了甲基磺酸盐酸性镀锡的发展过程及优点,介绍了不同添加剂(如表面活性剂、抗氧化剂、光亮剂等)在甲基磺酸盐酸性镀锡中的作用,探讨了添加剂在电沉积中作用的机理,对添加剂的应用进行了展望.     

乙醇丙酮体系的广义二维相关近红外光谱分析

利用近红外及二维相关光谱进行了丙酮乙醇两种试剂体系的结构分析。首先检测30~50℃范围内(每隔2℃)的近红外光谱,结合近红外光谱、二维相关光谱及相关文献,对乙醇丙酮体系的分子结构(特别是氢键)进行了分析。近红外光谱的特征峰在一维图上变化不明显,借助于二维相关分析,提高了分辨率和可解释性。特别是分析了两种氢键羟基的存在,发现了烯醇羟基形成氢键及甲基与羰基形成氢键的证据,确定了不同分子结构之间的变化先后顺序,并进行了本体系近红外峰的归属。研究结果将有利于更深刻地理解该类试剂,为其进一步研究和使用提供参考。     

新型聚天冬氨酸酯聚脲的合成、结构与性能研究

通过二步法:(1) 4,4'-二氨基环己基甲烷(PACM)或3,3'-二甲基-4,4'-二氨基环己基甲烷(Laromin C260)与马来酸二乙酯的Michael加成反应,(2) 反应(1)产物与E-51环氧树脂的加成反应,合成了新型聚天冬氨酸酯(PAEs).与现有Michael加成法相比,二步法能明显缩短合成反应时间,更适合工业化生产.进一步通过PAEs与4,4'-二环已基甲烷二异氰酸酯(H12MDI)/聚四亚甲基二醇(PTMG)预聚物反应,常温合成了2种PAEs聚脲.采用FT-IR、1H-NMR和GPC等表征了PAEs,并采用FT-IR和DMA考察了PAEs聚脲的结构形态、反应活性和力学性质.研究结果表明,聚脲硬段氨基氢键化程度高,氢键键长为3.04 ?;脲羰基的氢键化程度分别为74.4%和73.2%,提高固化温度,有助于脲羰基氢键的形成.PAEs聚脲呈现微相分离的形态,是低活性、高强度的弹性体涂层材料.     

毛细管气相色谱法测定[bmmim][NTf_2]中的无限稀释活度系数

采用毛细管气相色谱法,应用3根不同膜厚的1-丁基-2,3-二甲基咪唑双(三氟甲烷磺酰)亚胺盐([bmmim][NTf2],1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide)离子液体壁涂毛细管柱,分别在40、50和60℃下测定了60种有机物的保留时间。使用改进方程计算得到了60种有机物在[bmmim][NTf2]中的无限稀释活度系数,并通过无限稀释活度系数计算得到了无限稀释选择性系数、容量因子等热力学参数。通过线性拟合求得[bmmim][NTf2]的LSER模型关联参数,发现最显著的作用力是偶极/极化作用和氢键碱性,且[NTf2]?的氢键碱性小于[dca]?,与[PF6]?相近,同时验证了咪唑阳离子的2位H被甲基取代后,氢键酸性明显降低。此外,探讨了将[bmmim][NTf2]用于乙腈-乙醇、丙酮-环己烷、苯-环己烷、甲苯-甲基环己烷等难分离体系分离的可行性。     

甲基效应对二水合甘氨酸复合体性质的影响

采用B3LYP/6-31++G(d,p)方法研究二水合丙氨酸中性复合体转化为两性复合体的质子迁移过程以及两性离子复合体间的氢键迁移过程,与二水合甘氨酸复合体中相应过程作比较,探讨甲基效应。结果发现:(1)甲基诱导效应使二水合甘氨酸两性复合体的分子内氢键增长超过0.0024 nm,对分子间氢键影响很小;(2)甲基效应使两性体系更稳定(结合能增加3.59 k J·mol-1以上);(3)甲基效应对氢键迁移的能垒影响不大;但是有利于质子迁移(能垒降低3.1 k J·mol-1)。     

G-四联体结构在生物传感器中的应用进展

G-四联体结构是由多聚鸟嘌呤序列通过Hoogsteen氢键配对形成的笼式结构.该结构具有独特的化学性质,如可以特异性地与N-甲基卟啉二丙酸Ⅸ(NMM)化合物结合,产生荧光以及具有过氧化物酶活性等.据此科学家开发了一些生物传感器,并取得了丰硕的成果.此类传感器大多是通过被检物质引起DNA结构的变化,进而引起荧光信号和过氧化物酶活性变化,最终达到检测的目的.对基于G-四联体结构开发的生物传感器检测金属离子、有机大分子、核酸和生物酶等物质的研究进展进行了综述.     

酸性离子液体催化合成N，N’-亚甲基双丙烯酰胺

以N-甲基咪唑、2-氯乙基苯、硫酸氢钾合成1-甲基-3-[α-甲基-(4-磺酸苄基)]咪唑硫酸氢盐酸性离子液体.考察了酸性离子液体在甲醛和丙烯腈的反应中的催化性能,确定了最佳反应条件:n(甲醛):n(丙烯腈)=1.2:1.0,酸性离子液体用量为丙烯腈质量的8.0%,反应温度70℃,反应时间2.0h.在该条件下N,N'-亚甲基双丙烯酰胺的收率大于92%,纯度为98%以上,且反应结束后产物易于分离,酸性离子液体循环使用5次以上.     

溶剂对磺胺甲基嘧啶溶剂化合物形成的影响

采用悬浮转化法对磺胺甲基嘧啶溶剂化合物在醇类、酯类和酰胺类等17种溶剂中进行了筛选研究,采用粉末 X 射线衍射、热重分析、扫描电镜和傅里叶红外光谱对磺胺甲基嘧啶溶剂化合物进行了表征,成功制备出磺胺甲基嘧啶与N,N-二甲基甲酰胺、N,N-二甲基乙酰胺、N-甲基吡咯烷酮溶剂化物和二甲基亚砜的4种溶剂化合物。热重结果表明它们均属于化学计量比为1∶1的溶剂化合物;扫描电镜分析发现在溶剂化合物形成过程中,晶体的形态由接近正方体的块状晶体变为片状与棒状晶体;傅里叶红外表征分析证实了溶剂化合物中溶剂与溶质分子形成分子间氢键。分析所用的17种溶剂的分子结构、氢键供体和受体能力等性质,确定了磺胺甲基嘧啶容易与氢键受体能力强的溶剂形成相应溶剂化合物。对比分析了晶体中分子的堆积效率,进一步证实了磺胺甲基嘧啶形成氢键溶剂化合物。根据磺胺甲基嘧啶和溶剂化合物的单晶结构,分析氢键溶剂化合物形成前后分子堆积、结构合成子和氢键网络的变化,磺胺甲基嘧啶晶型Ⅱ及其溶剂化合物的四种结构中均形成一维的椅子形氢键网络,对于三种溶剂化合物,除了磺胺甲基嘧啶分子间形成的氢键网络,磺胺甲基嘧啶分子氨基中另一个氢原子与溶剂分子的氧原子相连形成分子间N—H…O氢键。结果表明氢键在溶质与溶剂间的超分子自组装过程中起决定作用,是影响溶剂化合物形成的关键因素。     

热塑性聚氨酯弹性体中的氢键作用-II.红外热分析

应用定量的红外热分析 ,研究了三种由聚四氢呋喃 ( Mn=2 0 0 0 )、4,4’-二苯基甲烷二异氰酸酯、N-甲基二乙醇胺或 1 ,4-丁二醇合成的 TPU中氢键化程度及其温度依赖性。并通过Van't Hoff作图 ,求出氢键解离的热焓和熵变化。     

Hyperbranched polyesters with internal and exo‐presented hydrogen‐bond acidic sensor groups for surface acoustic wave sensors

Three hyperbranched aromatic polyesters carrying both internal and exo‐presented hydrogen‐bond acidic phenol, carboxylic acid, or mixed phenol/acetoxy groups were coated onto 500 MHz surface acoustic wave (SAW) sensor platforms, and sensor responses to the nerve agent simulant dimethyl methylphosphonate (DMMP) and the explosives simulant dinitrotoluene (DNT) were studied. All three hyperbranched polyesters gave strong responses to DMMP, and the hyperbranched polyester carrying carboxylic acid groups gave a particularly strong response. The hyperbranched polyester carrying phenol groups gave the best response to DNT of the three polymers studied. The DMMP and DNT responses of the three hyperbranched polyesters were also compared with hyperbranched SAW sensor polymers carrying exo‐presented phenolic sensor groups only, and also with linear SAW sensor polymers carrying phenolic sensor groups. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A surface acoustic wave sensor study of polyimide thin film surface treatments - effect on water uptake

The effects of surface treatments on the water uptake in thin (1 μm) polyimide (PI) films were studied using a surface acoustic wave (SAW) sensor, X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ERIR) spectroscopy, and contact angle measurements. Surface modification of PI films can affect film properties such as water uptake and adhesion. These properties, in turn, affect the performance and reliability of the devices in which these films are used. The ability to nondestructively study the results of various surface modification techniques in situ, prior to deposition of a metal layer for example, would be of particular benefit in the fabrication process. The results of this work indicate that the SAW sensor can measure extremely small amounts (< 0.003 μg) of water uptake in thin (1.2 μm) PI films. Also, that the water uptake of PI films, as measured by the SAW sensor, is particularly sensitive to sputter cleaning, sputtering/ KOH, and Teflon AF surface treatment. The SAW, XPS, ERIR, and contact angle studies of the Teflon AF treated PI indicate that the concentration of Teflon AF is very high in the surface region of the PI and decreases into the bulk of the film. This work suggests utility of the SAW sensor as a nondestructive and in situ method for monitoring the surface properties of thin polymers in process control applications.     

New macromolecular silane coupling agents synthesized by living anionic polymerization; grafting of these polymers onto inorganic particles and metals

New macromolecular silane coupling agents, which are end-triethoxysilylated poly(styrene) and poly(tert-butylmethacrylate), were investigated as possible inorganic particle and metal surface treatment agents. These polymers containing poly(styrene) and poly(tert-butylmethacrylate) as the main chain, were prepared by living anionic polymerization. Grafting of the polymers onto inorganic particles and metals was performed via the hydrolysis of the triethoxysilyl group using either acidic or basic catalyst. n-Butylphosphate was used as the catalyst for grafting onto inorganic substances having an acidic surface such as silica. However, in the case of grafting onto inorganic substances having a basic surface, tetrabutylammoniumhydroxide was employed as the catalyst. Contrary to expectations, grafting onto titania was successful even in the absence of a catalyst. Particles grafted with these polymers showed excellent dispersibility in organic medium, in which the polymers are soluble. This phenomenon is in contrast to that for particles treated with polymers possessing triethoxysilyl groups at random positions of the chain or those treated with trimethylsilyl groups. Surface tension measurements of metal substrates coated with the grafted polymers, were found to be identical to the values obtained for the bulk polymers.     

Hydrogen-bond acidic functionalized carbon nanotubes (CNTs) with covalently-bound hexafluoroisopropanol groups

Hydrogen-bond acidic fluoroalcohol groups are directly attached to the backbone of single walled carbon nanotubes (SWCNTs) via carbon-carbon bonds without the introduction of intermediate heteroatoms. Hexafluoroisopropanol functional groups are exceptionally strong hydrogen-bond acids, and are added to the nanotube surface (via the substituted benzene para position) as 2-phenyl-1,1,1,3,3,3-hexafluoro-2-propanol (i.e., -(p-C₆H₄)C(CF₃)₂OH) using the aryl diazonium approach to create hydrogen-bond acidic carbon nanotube (CNT) surfaces. These groups can promote strong hydrogen-bonding interactions with matrix materials in composites or with molecular species to be adsorptively concentrated and sensed. In the latter case, this newly developed material could potentially find useful application in chemical sensors and in CNT-based preconcentrator devices for the detection of hydrogen-bond basic analytes such as chemical warfare agents and explosives, as has been demonstrated for fluoroalcohol-containing polymers.     

The nature of polymer grafts and substrate shape on the surface degradation of poly(l‐lactide)

Surface grafting of functional polymers is an effective method to alter material properties and degradation behavior. Two different substrate shapes of poly(l ‐lactide) (PLLA), i.e., films and microparticles, were surface‐grafted with hydrophilic monomers, and their surface degradation was monitored. Surface grafting with a hydrophilic and acidic polymer graft [acrylic acid (AA)] induced large alterations in the surface morphology and topography of the films. In contrast, hydrophilic and neutral polymer grafts [acrylamide (AAm)] had no significant effect on the surface degradation behavior, while the PLLA reference and co‐monomeric (AA/AAm) polymer‐grafted samples exhibited intermediate surface degradation rates. The grafted PAA chains induced a local acidic environment on the surface of the substrates, which in turn catalyzed the surface degradation process. This effect was more pronounced in the films than in the microparticles. Thus, the nature of the grafted chains and substrate geometry were shown to affect the surface degradation behavior of PLLA substrates. © 2015 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42736.     

Polymer structure formed in radiation-induced graft polymerization

Methacrylic acid (MAA) and methyl methacrylate (MMA) were grafted onto nylon 6, cellulose triacetate, cotton, viscose rayon, and polyester fibers, and the stereoregularities of the grafted polymers were determined. The graft polymerization was carried out with preirradiation techniques using γ-rays from a Co 60 source. The grafted copolymers were then separated from the homopolymers by Soxhlet extraction. The grafted (branch) polymers were isolated from the trunk polymers by acid hydrolysis and their stereoregularity was determined with a 100 MHz NMR spectrometer. The stereo-regularity of PMAA or PMMA grafted onto viscose rayon or cotton fiber was different from that of the polymers formed in ordinary radical polymerization.     

A novel gas sensor from crystalline polymer-grafted carbon black: responsibility of electric resistance of composite from crystalline polymer-grafted carbon black against solvent vapor

Summary Crystalline polymers, such as poly(ɛ-caprolactone) (PCL), poly(ethylene adipate) (PEA), and polyethylene (PE), were successfully grafted onto carbon black surface by direct condensation of terminal groups of these polymers with carboxyl groups on the surface using N,N'-dicyclohexylcarbodiimide as a condensing agent. The electric resistance of a composite prepared from these crystalline polymer-grafted carbon black drastically increased to 10⁴–10⁵ times of initial resistance in good solvent vapor of grafted polymer and returned to initial resistance when it was transferred into dry air. However, the change of electric resistance of the composite hardly observed in poor solvent vapor. These results suggest that these composite can be applied as a novel gas sensor. Received: 18 February 1999/Accepted: 25 March 1999     

Polymer structure formed in radiation-induced graft polymerization. II

Methyl methacrylate was grafted onto viscose rayon, wood pulp, cellophane, and poly(vinyl alcohol) with preirradiation techniques using γ-rays from a Co-60 source, and the stereoregularities of the grafted polymers separated from the trunk polymers and homopolymers were determined. The stereoregularity of the polymers grafted onto rayons is different from that of the polymers grafted onto wood pulp, mercerized wood pulp, cellophane, and poly(vinyl alcohol), confirming our previous results.     

基于点击化学和可逆加成-断裂链转移自由基聚合合成极性链接枝聚丁二烯

以1-硫代甘油作为改性剂、聚丁二烯为主链,通过热引发和光引发合成了侧基含有羟基的聚丁二烯,以S-1-十二烷基-S′（α-α′-二甲基-α′′乙酸）-三硫代碳酸酯作为可逆加成-断裂链转移自由基聚合试剂、偶氮二异丁腈为引发剂,合成了端羧基聚N,N-二甲基丙烯酰胺,然后将两种官能化的聚合物进行酯化反应制得聚N,N-二甲基丙烯酰胺接枝聚丁二烯。结果表明,采用光引发可以显著提高点击化学的反应效率。用核磁共振氢谱证实了产物含羟基聚丁二烯和端羧基聚N,N-二甲基丙烯酰胺以及接枝聚合物的结构,并显示通过这种方法所制备接枝聚合物的接枝链数目和长度均可控。     

声表面波传感器温度频率特性的数值分析

利用ANSYS软件对声表面波传感器进行温度频率特性的数值模拟研究。分析了在一定压力情况下,基于氮化铝压电薄膜铝叉指换能器的延迟型传感器结构内部的温度有限元分布情况。结果表明外界自然对流对传感器内部的温度场及应力场分布影响很小。并模拟计算出温度与输出串联谐振频率变化的关系,通过数据拟合得出,SAW传感器的输出谐振频率与环境温度变化呈良好的线性关系,因此可应用于温度的精确测试。