In situ SIMS analysis and reactions of surfaces prepared by soft landing of mass-selected cations and anions using an ion trap mass spectrometer

Mass-selected polyatomic cations and anions, produced by electrosonic spray ionization (ESSI), were deposited onto polycrystalline Au or fluorinated self-assembled monolayer (FSAM) surfaces by soft landing (SL), using a rectilinear ion trap (RIT) mass spectrometer. Protonated and deprotonated molecules, as well as intact cations and anions generated from such molecules as peptides, inorganic catalysts, and fluorescent dyes, were soft-landed onto the surfaces. Analysis of the modified surfaces was performed in situ by Cs⁺ secondary ion mass spectrometry (SIMS) using the same RIT mass analyzer to characterize the sputtered ions as that used to mass select the primary ions for SL. Soft-landing times as short as 30 s provided surfaces that yielded good quality SIMS spectra. Chemical reactions of the surfaces modified by SL were generated in an attached reaction chamber into which the surface was transferred under vacuum. For example, a surface on which protonated triethanolamine had been soft landed was silylated using vapor-phase chlorotrimethylsilane before being returned still under vacuum to the preparation chamber where SIMS analysis revealed the silyloxy functionalization. SL and vapor-phase reactions are complementary methods of surface modification and in situ surface analysis by SIMS is a simple way to characterize the products produced by either technique.     

TDI三聚体的合成研究

以一种碱金属羧酸盐K-1000作为甲苯二异氰酸酯(TDI)三聚反应的催化剂合成了以TDI三聚体为主要成分的多异氰酸酯固化剂。对合成工艺条件进行了探讨。结果表明,将反应温度控制在35℃,催化剂K-1000用量为0.06%时,用苯甲酰氯作为阻聚剂可得到性能基本稳定的TDI三聚体产品。     

含改性松香的丁二醇二缩水甘油醚固化反应动力学研究

设计了含改性松香无苯环的环氧固化体系和无松香的对照体系,分别是无松香体系Ⅰ：丁二醇二缩水甘油醚（BDGE）和甲基六氢苯酐（MeHHPA）;无规体系Ⅱ：丙烯酸松香（AR）、BDGE和MeHHPA;有规体系Ⅲ：丙烯酸松香基环氧树脂（ARE,由AR和BDGE预聚而来）和MeHHPA。对三体系的固化反应应用动态示差扫描量热仪（DSC）进行了研究,利用KAS法求得不同转化率下的表观活化能,通过整个反应过程反应活化能的变化,得到了三体系反应的内在机理,结果发现松香基的引入及引入顺序都对固化反应产生影响。     

Crystal structure of (4α,4aα,8aα)-(±)-octahydro-2-(phenylmethyl)-2H-1,2-benzoxazin-4-ol, 4-methylbenzenesulfonate(ester)

The title compound, a bicyclic tetrahydro-1,2-oxazine, crystallizes in a monoclinic lattice, space group P2₁/c, with a = 12.9809(18)Å, b = 12.920(2)Å, c = 13.631(2)Å, = 110.713(12)°, and Z = 4. The structure found in the solid state for this conformationally mobile molecule shows the tosyl group in an axial position and a benzyl group in an equatorial position of the bicyclic system.     

Molecular dynamics in a miscible polyester blend

The dynamic mechanical and dielectric spectra of a miscible polyester and polycarbonate blend are investigated with emphasis on the latter technique. It was found that relaxation spectra for the blends from both techniques are broader than those of the constituent homopolymers. This is ascribed to greater intermolecular coupling and concentration fluctuations within the blends. The composition at which the greatest coupling occurs is dependent on the relaxation technique used and is skewed towards the component which shows the highest degree of intermolecular coupling. A number of parameters, such as relaxation time of the polymer molecules in the blend and relaxation strength, are compared as a function of reduced temperature (experimental temperature scaled by the glass transition temperature). Whereas blend behavior is generally intermediate between that of the homopolymers, it appears as though mobility of compositions with low polyester content have a greater relaxation time and possess a higher activation energy when compared to a simple, weighted average of the corresponding homopolymer values. © 1996 John Wiley & Sons, Inc.     

Stereochemistry and mechanism of the conversion of 5-aminolaevulinic acid into porphobilinogen catalysed by porphobilinogen synthase

(3R)- and (3S)-Deuteriated forms of 5-aminolaevulinic acid have been synthesized and the (3R)-form shows a significantly larger isotope effect when incubated with porphobilinogen synthase from bovine liver and from Bacillus subtilis; based on this and on available crystal structures, a modified mechanism for the enzymic reaction is proposed.     

Unusual spin transition behavior in 2,6-bis((pyrazol-3-yl)-pyridine) iron(II)-bis-oxalato-platinate(II)

[Fe(bpp)2][Pt(ox)2].H2O (with bpp=2,6-bis(pyrazol-3-yl)-pyridine and ox=oxalate) was prepared, and its spin crossover behavior was characterized. The two-step spin transition behavior changes over several cycles. The original behavior is restored when the sample is allowed to relax for a week. Furthermore, the ST exhibits a strong dependence on the heating and cooling rate. Heating the compound at 1 K/min leads to a spin transition with a third step and a second plateau at gammaHS approximately 0.8. Quenching the sample to 77 K also affects the spin transition behavior. The kinetic relaxation is followed after quenching and after light-induced excited spin state trapping experiments.