Synthesis of Macrocyclic Arsinous Acid Estcrs

MacrocyclicarsinousacidestersareusuallypreparedbycondensationofdichloroalkylarsinesRAsCI,Iwithdidsinthepresenceoforganicalkali].ThemethoddescribedhereinvolvesthetransformationofintermediatefromItohis(dimethylamino)alkylarsineRAs(NMe,),2andthereactionof2withdidsindryTHFtoleadtotheformationoftitlecompounds.2canreactsmoothlywithdidsintheabsenceoforganicalkalitogeneratecorrespondingmacrocyclicarsinousacidesters4anddimethylaminewhichescapesfromthereactingsystemasagasinreflux.Althoughonemoreste…     

Dynamic mechanical properties of aluminum nitride/cyanate ester composites for high performance electronic packaging

Viscoelastic ature is one of the key features of polymeric composites. A series of cyanate ester (CE)‐based composites with different aluminum nitride (AlN) contents for high performance electronic packaging, coded as AlN/CE, were developed; the viscoelastic nature of AlN/CE composites was intensively investigated by employing dynamic mechanical analysis (DMA). Results show that the AlN content has a great effect on dynamic mechanical properties of AlN/CE composites. The storage modulus in the glassy region increases linearly with the addition of AlN as well as the increase of AlN content. Meanwhile, all composites also exhibit notably higher loss modulus than cured CE resin due to the appearance of new energy dissipation forms. In addition, the incorporation of AlN has a significant effect on damping factor peak. All reasons leading to these phenomena are analyzed from the view of structure–property relationship. Copyright © 2009 John Wiley & Sons, Ltd.     

Variation of anions in layered double hydroxides: Effects on dispersion and fire properties

Layered double hydroxides (LDHs) are interesting materials for nanocomposite formation because one can vary the identity of the metals, the anions and the stoichiometry to see the effect of these on the ability of the nano-material to disperse in a polymer and to see what effect dispersion has on the properties of the polymer. In this study, the anions 2-ethylhexyl sulfate (SEHS), bis(2-ethylhexyl) phosphate (HDEHP) and dodecyl benzenesulfonate (SDBS) have been utilized as the charge balancing anions to synthesize organo-LDHs. Nanocomposites of poly(methyl methacrylate) (PMMA) and polystyrene (PS) with organo-LDHs were prepared both by melt blending and bulk polymerization. X-ray diffraction and transmission electron microscopy were used to characterize the morphology of the nanocomposites while the thermal stability and fire properties of nanocomposites were studied by thermogravimetric analysis and cone calorimetry; the mechanical properties are also investigated. In general, it is easier to disperse these organo-LDHs in PMMA than in PS, but the sulfate cannot be dispersed at the nanometer level in either material. The addition of these organo-LDHs does not affect the mechanical properties. The best fire properties are obtained with the sulfonate LDH, SDBS; the reduction in the peak heat release rate is almost 50% for both polymers.     

盐酸催化合成α-萘乙酸甲酯

以α-萘乙酸、甲醇为原料,以浓盐酸为催化剂,通过酯化反应合成了植物生长调节剂萘乙酸甲酯。通过正交设计讨论了醇酸摩尔比、催化剂用量、反应时间等因素对酯化产率的影响。在α-萘乙酸50mmol,n(甲醇)：n(α-萘乙酸)=25,催化剂用量为α-萘乙酸质量的17％,反应时间2．0h,酯化温度65℃～69℃的最佳反应工艺条件下,产率97．4％。     

Structure Characterization and Thermal Properties of PMMA／Montmorillonite Nanocomposites via Emulsion Polymerization

Montmorillonite(MMT) modified with sodium silicate can change the arrangement of its layers fromedge-face and edge-edge to face-face. With the fine dispersion of the modified MMT in water, the cation-ex-change reaction was carried out with cetyltrimethyl ammonium bromide (CTAB) to obtain organo-montmoril-lonite (OMMT). As OMMT was uniformly dispersed in methyl methacrylate (MMA) monomer, PMMA/OMMT nanocomposites were formed via a common emulsion polymerization. The products were extractedwith hot acetone and characterized by FTIR, molecular weight, X-ray diffraction(XRD), transmission elec-tron microscopy(TEM), DSC and TGA. These results show that most of the OMMT layers have been exfo-liated, while the thermal stability is increased obviously. By means of FTIR spectral analysis, the ratios ofthe macromolecular radicals‘ termination of disproportionation patterns to combination are increased with theaddition of OMMT. This result further confirms the increase of the thermal degradation temperatures andglass transition temperatures of the PMMA/OMMT nanocomposites.     

Synthesis and MALDI-TOF-MS of PS-PMA and PMA-PS block copolymers

The synthesis of well-defined block copolymers from styrene and methyl acrylate via ATRP is discussed in this contribution. Kinetic studies on these block copolymerizations as well as characterization studies were performed to investigate the monomer composition in the respective PS and PMA blocks. MALDI-TOF-MS was performed to clarify the exact number of repeating units of each block and the total number of units in the block copolymer. Block copolymers up to 22 kDa could be analyzed by MALDI-TOF-MS, whereby polymers with PMA as first block showed a large second distribution corresponding to PMA homopolymers. However, SEC demonstrated that only a small amount of homopolymer was present indicating that care needs to be taken with interpreting MALDI-TOF-MS data, which is a qualitative rather than a quantitative technique.     

Synthesis of 2-arylacrylic esters from aryl methyl ketones via Wittig reaction/singlet oxygen ene reaction

An efficient synthetic method has been developed for the synthesis of 2-arylacrylic esters from the corresponding aryl methyl ketones via Wittig reaction and singlet oxygen ene reaction. Wittig reaction to aryl methyl ketones with (methoxymethyl)triphenylphosphonium chloride in basic condition afforded the methyl enol ethers, and then 2-arylacrylic esters were obtained by singlet oxygen ene reaction, followed by tosylation and elimination in one-pot to the methyl enol ethers in good yields.     

Synthesis of Poly(methyl methacrylate) Nanosize Particles by Differential Microemulsion Polymerization

Poly(methyl methacrylate) nanosize particles were synthesized by a differential microemulsion polymerization process. Sodium dodecylsulfate and ammonium persulfate were used as the surfactant and initiator, respectively. The effects of reaction conditions on the particle size have been investigated. A particle size of less than 20 nm in diameter has been achieved with surfactant/monomer and surfactant/water weight ratios of 1:18 and 1:120, i.e. much milder conditions than those previously reported in the literature.

TEM image of nanoparticles prepared via differential microemulsion polymerization.     

Efficient Method for Demethylation of Aryl Methyl Ether Using Aliquat-336

A rapid method for selective cleavage of aryl methylethers can be achieved in the presence of a protic acid and a catalytic amount of phase-transfer catalyst (Aliquat-336). Aliquat-336 accelerates the rate of reaction and affords the corresponding phenols in excellent to good yields on a wide variety of substrates.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

A series of mono and diesters of itaconic acid: Synthesis and structural determination

Summary A series of mono and diesters of itaconic acid containing alkoxy and sulfide side chains of variable lengths has been synthesized. Their structures have been established on the basis of their spectral data.

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Eine Serie von Mono- und Diestern von Itaconsäure: Synthese und Strukturbestimmung

Zusammenfassung Es wurde eine Serie von Mono- und Diestern von Itaconsäure mit Alkoxy- und Sulfidseitenketten variabler Länge synthetisiert. Die Strukturaufklärung erfolgte mittels spektroskopischer Daten.