Oligomer and Polymer Formation in Hexamethylcyclotrisiloxane (D<Subscript>3</Subscript>) – Hydrosilane Systems Under Catalysis by tris(pentafluorophenyl)borane

Summary Reactions of hexamethylcyclotrisiloxane, D₃, with 1,1,3,3-tetramethyldisiloxane, ^HMM^H, 1,1,1,3,3-pentamethyldisiloxane, ^HMM, phenyldimethylsilane and phenylmethylsilane catalyzed by tris(pentafluorophenyl)borane were studied. These reactions lead to ring opening of D₃ by the SiH reactant producing open chain oligomers with hydrosilane functionality at one or both chain ends. The reactivity of the hydrosilanes toward D₃ decreases in the series: PhMeSiH₂ > ^HMM^H > PhMe₂SiH > ^HMM. Competitive self-oligomerization of ^HMM^H and ^HMM also occurs. Primary products of these processes are able to enter into reactions with the SiH and D₃ reactants; some also undergo cyclization. Thus, consecutive and competitive processes lead to a series of various oligohomologues. Gas chromatography in conjunction with chemical ionization mass spectroscopy permitted identification of structure and determination of the basic directions of these oligomerization processes. Polysiloxanes of higher molecular weight may be also formed in some of these systems. The reactions, which occur in the systems studied, are rationalized on the basis of the mechanism involving the hydride transfer from silicon to trivalent boron. This includes the transient formation of tertiary trisilyloxonium borate which decomposes by the hydride transfer to one of the silicon atoms of the trisilyloxonium center. Footnote: This paper is dedicated to Professor Ian Manners in recognition of his significant contributions to the field of organometallic polymers.     

Studies of cyclic and linear poly(dimethyl siloxanes): 12. Observation of diffusion behaviour by quasielastic neutron scattering

High resolution neutron scattering experiments have been used to observe the diffusive motion of low molecular weight linear and cyclic poly(dimethyl siloxane) molecules in dilute solution in deuterated benzene. Diffusion coefficients (D) and hydrodynamic radii (R_H) have been compared with values obtained by light scattering for higher molecular weight samples and with radii of gyration (R_g) obtained by small-angle neutron scattering. While the ratio $\text{D}{}_{\mathrm{<mtext>ring</mtext>}}\text{D}{}_{\mathrm{<mtext>chain</mtext>}}$ is close to the predicted value of 0.85, the ratio $\text{R}{}_{\mathrm{g}}\text{R}{}_{\mathrm{<mtext>H</mtext>}}$ falls below the theoretical value for both ring and chain molecules. The scattering curves show effects arising from both centre of mass diffusion and internal molecular motion, and the observed inverse correlation times are compared with calculated behaviour as a function of scattering vector, Q.     

含二苯甲酮基的有机硅光引发体系

在UV照射下,用含巯基的有机硅化合物与聚甲基乙烯基硅氧烷加成硫化虽有专利报道,但该反应体系是以二苯甲酮类化合物作为光敏剂。当我们进行这方面研究时,发现二苯甲酮与有机硅氧烷预聚物相容性差,从而影响光加成反应的速度。为了改善光敏剂与有机硅预聚物的相容性,本文合成了具二苯甲酮基团的环状有机硅氧烷及其高聚物作为光敏剂。我们的合成路线是用硅氢加成反应,制备了文献没有报道的具二苯甲酮侧基的环状硅氧烷,然后将其与八甲基环四硅氧烷一起进行开环聚合,得到了具有二苯甲酮侧基的聚有机硅氧烷,其反应过程如下:     

二苯并（2，3，2＇，3＇，bg）－1H，6H，1，4，6，9－四氮－5－钛螺环［4，4］－5，5－二氯化物

ｏ－苯二胺与四氯化钛反应合成聚合物的模型化合物钛杂咪唑啉。该化合物经元素分析、红外光谱、质谱测试。     

建筑防水涂料用硅丙乳液的制备与性能

介绍了有机无机复合建筑防水涂料用硅丙乳液的研制背景、制备方法及主要性能。所制备的硅丙乳液有机硅含量达12％，其与水泥和细砂集料混合均匀后形成的有机无机复合防水涂料对常用建筑材料粘接力强，形成的弹性胶膜吸水率低、防水性好、耐老化性高、产品性能稳定。     

亲水性聚醚/氨基硅烷乳液成膜形貌及应用

利用透射电子显微镜(TEM)、纳米粒度仪、扫描电镜(SEM)仪等仪器,对亲水性聚醚氨基硅(HPEAS)乳液的粒径及其分布、在纤维表面的成膜形态进行了表征.结果表明:亲水性聚醚氨基硅乳液的平均粒径为30 nm,Zeta电位为+25.5 mV,其在纤维表面包裹有一层树脂膜,能导致纤维表面的条纹状沟壑消失,使纤维表面相对光滑.当硅乳用量为4~5 g/L时,经整理的织物弯曲刚度明显降低,白度基本不变,静态吸水时间仅为2.16 s,保持纤维原有的风格.     

Conformational changes of Mal d 2, a thaumatin-like apple allergen,induced by food processing

Mal d 2, a thaumatin-like protein from apple was previously described to react to almost 75% of the apple allergic patient sera. Based on the molecular structure of this protein, the present study focused on the conformational stability of Mal d 2 in relation to in vitro IgE-binding under different physico-chemical conditions and proteolysis. The structural integrity of Mal d 2 was monitored using SDS–PAGE, Western blotting using polyclonal antibodies and human sera, fluorescence spectrometry and circular dichroism. Results confirmed the stability of Mal d 2. However, Mal d 2 was reactive to human serum IgEs mainly after reduction of disulphide bridges fixing the α-helical domain II. Contrary to previous assumptions, the current findings suggest that the allergenic epitopes of Mal d 2 are hidden inside the protein structure and none of the rigorous conditions applied in industrial juice processing or digestive proteolysis enhance or reduce the binding to IgE molecules.     

反应性氨基硅乳整理剂的制备及应用

用数均摩尔质量为２６４０ｇ／ｍｏｌ的含Ｎ－β－氨乙基－γ－氨丙基的硅油与０．８％（相对于硅油的质量分数,下同）的甲基三乙氧基硅烷或０．６％的γ－（２,３－环氧丙氧基）丙基三甲氧基硅烷在９０～１１０℃反应１～４ｈ;再分别用脂肪醇聚氧乙烯醚、乙二醇单丁醚和消也化,可制得反应性氨基硅乳ＲＡＳ－、和ＲＡＳ－２,将其用于聚酯／胶粘共混纤维织物的整理,轧余率约７０％,织物经１００℃烘干,１８０℃固化３０ｓ,可     

Efficacy of ethylene‐diamine‐tetra‐acetic acid associated with chlorhexidine on intracanal medication removal: A scanning electron microscopy study

The aim of this study was to evaluate the effectiveness of 17% ethylene‐diamine‐tetra‐acetic acid (EDTA) used alone or associated with 2% chlorhexidine gel (CHX) on intracanal medications (ICM) removal. Sixty single‐rooted human teeth with fully formed apex were selected. The cervical and middle thirds of each canal were prepared with Gates Glidden drills and rotary files. The apical third was shaped with hand files. The specimens were randomly divided into two groups depending on the ICM used after instrumentation: calcium hydroxide Ca(OH)₂+CHX or Ca(OH)₂+sterile saline (SS). After seven days, each group was divided into subgroups according to the protocol used for ICM removal: instrumentation and irrigation either with EDTA, CHX+EDTA, or SS (control groups). All specimens were sectioned and processed for observation of the apical thirds by using scanning electron microscopy. Two calibrated evaluators attributed scores to each specimen. The differences between the protocols for ICM removal were analyzed with Kruskal‐Wallis and Mann‐Whitney U tests. Friedman and Wilcoxon signed rank tests were used for comparison between the score of debris obtained in each root canal third. Remains of Ca(OH)₂ were found in all specimens independently of the protocol and ICM used (P > 0.05). Seventeen percent EDTA showed the best results in removing ICM when used alone (P < 0.05), particularly in those associated with CHX. It was concluded that the chelating agent 17% EDTA significantly improved the removal of ICM when used alone. Furthermore, the type of the vehicle associated with Ca(OH)₂ also plays a role in the ICM removal. Microsc. Res. Tech. 77:735–739, 2014. © 2014 Wiley Periodicals, Inc.     

Factors Influencing Destruction of Triacetone Triperoxide (TATP)

Acid catalyzes the formation of triacetone triperoxide (TATP) from acetone and hydrogen peroxide, but acid also destroys TATP, and, under certain conditions, converts TATP to diacetone diperoxide (DADP). Addition of strong acids to TATP can cause an explosive reaction, while reaction with dilute acid reduces the decomposition rate so drastically that gentle destruction of TATP is impractical. However, combined use of dilute acid with slightly solvated TATP made gentle destruction of TATP feasible. Variables including acid type, concentration, solvent and ratios thereof have been explored, along with kinetics, in an attempt to provide a field‐safe technique for gently destroying this homemade primary explosive. The preferred method is moistening TATP with an alcoholic solution (aqueous methanol, ethanol, or iso‐propanol) followed by addition of 36 wt‐% hydrochloric acid. Preliminary experiments have shown the technique to be safe and effective for destruction of hexamethylene triperoxide diamine (HMTD), as well.