Characterization of mixtures of biocidal oligoguanidines by capillary electrophoresis and high-performance liquid chromatography coupled to mass spectrometry

The polycondensation of guanidine hydrochloride and 2,2′-(ethylenedioxy)bis(ethylamine) leads to various types of oligomeric guanidines exhibiting a broad spectrum of biocidal activities. In the present work a reversed-phase high-performance liquid chromatographic method with a gradient consisting of aqueous 0.1% trifluoroacetic acid and acetonitrile as mobile phase has been developed to separate these oligoguanidines according to type and chain length. The combination with electrospray mass spectrometry allowed the identification of the various compounds. By this technique, some structures already suggested in the literature could be confirmed, and several additional oligoguanidines not yet reported could be identified. As a complementary technique, capillary zone electrophoresis was investigated. Best results were obtained with carrier electrolytes consisting of phosphoric acid in water/acetonitrile mixtures. Although the number of peaks that could be separated by the electrophoretic method was considerably lower than in case of the chromatographic method, capillary electrophoresis in combination with UV detection at 195 nm may still be a fast method suitable for quantitation of some of the major compounds and for monitoring the reaction rate during the polycondensation reaction.     

Processable polyisoimide polymer blends for application as thermally stable adhesives for composites and advanced metal alloys

Polyimides are effective thermally stable bonding agents for substrates including titanium, aluminum alloys, steel alloys, metal matrix composites, and polymer/fiber composites with good tolerance toward elevated temperature and humidity. Problems associated with polyimide adhesives, including high processing temperatures and pressures and high melt viscosity, can be partially or totally alleviated by use of blends of polyisoimides. During thermal processing, the polyisoimides are isomerized to their polyimide modifications.     

表面活性剂与叶酸的相互作用及其对光氧化降解的影响

表面活性剂与有机小分子作用不仅能提高表面活性剂的聚集能力,还能提高小分子的溶解度、稳定性等应用性能,因此研究二者之间的相互作用机理对于促进表面活性剂的发展和实际应用具有重要意义。本工作提出了一种利用功能有机小分子调控表面活性剂聚集行为,进而提高不稳定小分子自身稳定性的新策略。利用表面张力、紫外可见吸收光谱、荧光光谱、动态光散射、等温滴定量热和核磁共振技术研究了在p H为7.0时,叶酸分别与十二烷基硫酸钠(SDS)、十二烷基三甲基溴化铵(DTAB)、季铵盐Gemini 12-6-12和季铵盐线性三聚12-3-12-3-12四种表面活性剂之间的相互作用及其导致的叶酸光氧化降解性能的变化,结果表明,阴离子表面活性剂SDS抑制叶酸光氧化降解的效率较低,而阳离子表面活性剂都能够显著抑制叶酸的光氧化降解,且随着表面活性剂寡聚度的增加,抑制效果增强,所需表面活性剂的浓度显著降低,寡聚表面活性剂12-3-12-3-12的抑制效率高达96%。     

低聚芴及其衍生物吸收和发射光谱性质的量子化学研究

用DFT/B3LYP方法对低聚物(PF)_2n和(PFDBO)_n(n=1-4)体系进行了全优化,计算得到两个系列低聚物的电离能P_I(v,a)、电子亲和势E_A(v,a)、空穴抽取能E_{HP和电子抽取能EEP等相关能量,并用ZINDO和TD-DFT方法计算其吸收光谱,分析了两系列总能量和HOMO-LUMO能隙随n递增的变化规律及对低聚物稳定性和光谱性质的影响,推断高聚物的发光性质.用CIS方法优化低聚物的S1激发态结构并分析其与发射光谱的关系.计算结果表明,这两个系列低聚物激发态结构中都有使所有骨架原子共平面的趋势.由于插入CH2OCH2,使PFDBO的七元环部分发生较大的扭曲(两个苯环间成42.5°±0.5°的二面角),致使有效共轭链被破坏、能带带隙变宽、吸收发射光谱波长变短.}     

Semi-Quantitative Determination of Free Cyclic and Linear Polytetrahydrofurane in Coatings Using Critical Chromatography

Summary Liquid chromatography at critical conditions (LCCC) is being used more frequently, especially for the determination of cyclic structures in a matrix of the parent linear molecules, analyses that cannot be performed easily by other techniques. In practice, analyses are often more complex than separating the linear from the cyclic structures, e.g. in the determination of low concentrations of free (linear and cyclic) polyols like polytetrahydrofurane (pTHF) in functional polymers and coatings. To this end different chromatographic phase systems at the critical conditions for the polyols were investigated to obtain the maximum amount of information. The identification of different oligomeric series was performed by means of an on-line coupling of LCCC with atmospheric pressure chemical ionization – mass spectrometry (APCI-MS). Mass summated chromatograms were introduced to improve the signal to noise ratio of specific oligomeric series. MS cannot be used for quantitative purposes here; therefore the evaporative light scattering detector (ELSD) and the refractive index (RI) detectors were evaluated for routine analyses. Specific tailing problems observed with a drift tube in the ELSD are discussed. Two LCCC systems (reversed phase and normal phase) were compared for best selectivityPresented at: International Symposium on Separation and Characterization of Natural and Synthetic Macromolecules, Amsterdam, The Netherlands, February 5–7, 2003     

无皂乳液聚合

本文综述了无皂乳液聚合的理论研究,如核生成及成长机理、无皂乳液的制备方法、胶乳颗粒的结构及性能以及无皂乳液聚合技术的进展情况。     

Preparation of novel fluoroalkyl end-capped oligomeric nanoparticles-encapsulated hibitane

Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer [R_F-(DOBAA)_n-R_F] reacted with hibitane in methanol at 90 °C to afford R_F-(DOBAA)_n-R_F oligomeric nanoparticles-encapsulated hibitane in good isolated yields. These fluorinated oligomeric particles-encapsulated hibitane were nanometer size-controlled very fine particles, and were found to exhibit a good dispersibility and stability in a wide variety of traditional organic solvents including fluorinated aliphatic solvents. Each dispersed solution with fluorinated nanoparticles afforded transparent colorless solution. These fluorinated nanoparticles were also found to exhibit a good antibacterial activity, and were applied to the surface modification of traditional organic polymers such as poly(methyl methacrylate).     

Catalytic fire retardant nanocomposites

In this paper the chemical activity of carbon nanotubes and polyhedral oligomeric silsesquioxane during thermal degradation and combustion of polymer nanocomposites is addressed. Indeed, polymer-nanofiller systems may exhibit chemical effects capable of thermal stabilisation of polymers as well as reduction of combustion rate and heat released, owing to catalytic effects induced by the nanofillers at high temperature.Carbon nanotubes in the presence of oxygen are shown to promote oxidative dehydrogenation in polyethylene with production of a stable surface layer of carbon char that provides an effective oxygen barrier effect. A similar action is performed by metal-containing polysilsesquioxanes dispersed in polypropylene.With either carbon nanotubes or metal POSS, partial carbonisation of the polymer matrix occurs during combustion, subtracting part of the organic polymer from combustion, targeting one of the major fire retardancy aim.     

The oligomeric approach – the electrochemistry of conducting polymers in the light of recent research

Electrochemical investigations on oligomeric model compounds (β-carotenoids) of polyacetylene varying the chain length in the range between 5 and 23 double bonds provide deeper insights into the redox properties of such systems. Furthermore, cyclic voltammetric studies of α,ω-diphenylpolyenes and phenylenevinylenes give clear evidence that the formation of the radical ions is followed by a rapid reversible dimerization between the oligomeric chains. The thermodynamic and kinetic parameters of the chemical reaction are presented. Applying these results to the properties of conducting polymers opens up new perspectives for interpreting charge storage and conductivity. Received: 27 May 1997 / Accepted: 6 October 1997