含有稠环侧链的聚硅氧烷的合成及其对加成型高温硫化硅橡胶性能的影响

将含有多乙烯基的聚硅氧烷与菲式环戊二烯酮和苊式环戊二烯酮分别在α-氯萘中进行Diels-Alder反应,生成含有稠环侧链的聚硅氧烷.该聚硅氧烷具有较好的耐热性.将其作为组分制成高温加成型硅橡胶,综合性能达到较高水平(高模量).随着其用量的增加,可使其耐热性能得到较大改善。     

Double hydrophilic block copolymers with switchable secondary structure as additives for crystallization control

The synthesis and folding behavior of two different series of double hydrophilic block copolymers based on polyethyleneglycol and short acidic polypeptide blocks are described. The employment of those species in the crystallization of CaCO₃ and BaSO₄ shows that in contrast to the expectations from biomineral examples, a random conformation of the peptide is more advantageous in mineralization control than an -helical arrangement of the same chain, which is contradictory to the epitaxial adsorption model in biomineralization. Otherwise, the peptide block copolymers support formation of superstructures similar to those already reported, e.g. well-defined spherical, prolate, and dumbbell morphologies are found.     

Explicit and implicit multi‐center integrations

We present truncated expansions of multicenter one‐electron nuclear attraction and two‐electron repulsion integrals over localized basis functions in terms of one‐ and two‐center integrals of “Coulomb,” “exchange,” and “hybrid” type. Two variants are discussed: the “Explicit Multi‐center Integrations” and the “Implicit Multi‐Center Integrations” (abbreviated as “EMCI” and “IMCI”, respectively). While EMCI also deals with individual integrals, the IMCI option is the more appealing one: it enables us to evaluate the entire matrix elements of “Restricted Hartree–Fock”‐type in a very effective and chemically meaningful way. Due to the diatomic nature of our expansions, integrations over “Slater‐Type Orbitals” become well‐feasible, too. © 2012 Wiley Periodicals, Inc.     

[2 + 2]-Cycloreversions

Four-membered rings can be cleaved thermally, Photochemically, or catalytically into two π bonded fragments. Theoretical calculations, kinetic studies, and investigations of stereo- and regioselectivity have been undertaken to clarify the question of whether the reaction involves one or two steps and to permit predictions on its course. [2 + 2]-Cycloreversions have been used to clarify the structure of four-membered rings, to prepare highly reactive π electron-systems and–in combination with a [2 + 2]-cycloaddition–to protect double bonds. The combination of a cycloaddition and-reversion can be used to convert a carbonyl group into an olefin. Starting with compounds containing annelated four-membered rings, compounds with two functional groups or large ring systems can be prepared. [2 + 2]-Cycloreversions have also been discussed in connection with storage of solar energy.     

Oxazepines and thiazepines,XXIV synthesis of optically active 2,3-dihydro-2-methyl-1,5-benzoxazepin-4(5H)-ones

Summary 2,3-Dihydro-2(R)-methyl-1,5-benzoxazepin-4(5H)-one [(R)-3] and its enantiomer (S)-3 have been synthesized via the optical resolution and subsequent chemical transformations of (±)-3-(2-nitrophenoxy)butyric acid (1). Compounds (R)-3 and (S)-3 were converted into optically active 1,5-benzoxazepines (R)-7–(R)-14 and (S)-15–(S)-32.

---

Oxazepine und Thiazepine, XXIV: Darstellung optisch aktiver 2,3-Dihydro-2-methyl-1,5-benzoxazepin-4(5H)-one

Zusammenfassung 2,3-Dihydro-2(R)-methyl-1,5-benzoxazepin-4(5H)-on [(R)-3] und sein Enantiomeres (S)-3 wurden durch Racemattrennung und weitere chemische Umsetzungen von (±)-3-(2-Nitrophenoxy)buttersäure (1) dargestellt. Die Verbindungen (R)-3 und (S)-3 wurden in die optisch aktiven 1,5-Benzoxazepine (R-7 bis (R)-14 und (S)-15 bis (S)-32 übergeführt.

     

Synthesis and Characterization of β‐Diketiminate Aluminum Compounds and Their Use in the Ring‐Opening Polymerization of ε‐Caprolactone

Four aluminum alkyl compounds, [CH{(CH₃)CN‐2,4,6‐MeC₆H₂}₂AlMe₂] ( 1 ), [CH{(CH₃)CN‐2,4,6‐MeC₆H₂}₂AlEt₂] ( 2 ), [CH{(CH₃)CN‐2‐iPrC₆H₄}₂AlMe₂] ( 3 ), and [CH{(CH₃)CN‐2‐iPrC₆H₄}₂AlEt₂] ( 4 ), bearing β‐diketiminate ligands [CH{(Me)CN‐2,4,6‐MeC₆H₂}]₂ (L¹H) and [CH{(Me)CN‐2‐ⁱPrC₆H₄}]₂ (L²H) were obtained from the reactions of trimethylaluminum, triethylaluminum with the corresponding β‐diketiminate, respectively. All compounds were characterized by ¹H NMR and ¹³C NMR spectroscopy, single‐crystal X‐ray structural analysis, and elemental analysis. Compounds 1 – 4 were found to catalyze the ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) with good activity.     

Formation of 3-[amino(aryl)-methylidene]-1,3-dihydro-2H-indol-2-ones involving ring transformation of 2-aryl-5-(2-aminophenyl)-4-hydroxy-1,3-thiazoles

The reaction of 3-bromooxindole with substituted (hetero)aromatic thioamides in acetonitrile was studied. At room temperature the reaction preferably gives products of ring transformation i.e. 2-aryl-5-(2-aminophenyl)-4-hydroxy-1,3-thiazoles (3b-f,h) whereas at elevated temperature products of an Eschenmoser coupling reaction, i.e. 3-[amino(aryl)-methylidene]-1,3-dihydro-2H-indol-2-ones (2b-f), are formed exclusively. There exist only two exceptions (4-methoxy and 2-pyridinthioamide) in which the Eschenmoser coupling reaction always takes place giving 2a and 2g. Also N-methylation of the starting 3-bromooxindole completely prevents formation of thiazoles. The prepared thiazoles 3b-f are unstable in solution and they undergo slow ring transformation to 2b-f. The rate limiting step of this rearrangement involves cleavage of an intermediary thiirane ring, which is slowed down by electron-withdrawing substituents on the thioamide (ρ = ?1.15).     

Synthesis of functionalized 4-nitroanilines by ring transformation of dinitropyridone with enaminones

2-Functionalized 4-nitroanilines were readily synthesized by ring transformation using 3,5-dinitro-2-pyridone and enaminones prepared from 1,3-dicarbonyl compounds and amines. Modification of the amino group and the ortho-position could be achieved by simply changing the enaminones. Using this strategy, functional groups such as acetyl, benzoyl, and ethoxycarbonyl groups could be introduced into the nitroaniline framework.     

Tunable dual wavelength fiber laser incorporating AWG and optical channel selector by controlling the cavity loss

In this paper, we propose and demonstrated a dual wavelength fiber laser (DWFL) based on the use of an erbium doped fiber (EDF) gain medium as well as an 1 × 24 Arrayed Waveguide Grating (AWG) together with two optical channel selectors (OCS) to provide channel spacing tunability. The output power of the two wavelengths is equalized by controlling the cavity loss in the DWFL using two Programmable Optical Attenuators (POAs). The widest spacing obtained from the DWFL is 18.13 nm while the narrowest spacing is 0.8 nm. The DWFL has good stability with only minor power fluctuations of less than 1.5 dB and a Side Mode Suppression Ratio (SMSR) of approximately 69.1 dB with peak fluctuations of less than 2.3 dB.     

A Monte Carlo method for simulating fractal surfaces

A Monte Carlo method is presented for simulating rough surfaces with the fractal behavior. The simulation is based on power-law size distribution of asperity diameter and self-affine property of roughness on surfaces. A probability model based on random number for asperity sizes is developed to generate the surfaces. By iteration, this method can be used to simulate surfaces that exhibit the aforementioned properties. The results indicate that the variation of the surface topography is related to the effects of scaling constant G and the fractal dimension D of the profile of rough surface. The larger value of D or smaller value of G signifies the smoother surface topography. This method may have the potential in prediction of the transport properties (such as friction, wear, lubrication, permeability and thermal or electrical conductivity, etc.) on rough surfaces.