Degradation of epoxy polymers: Part 1—Products of thermal degradation of bisphenol-A diglycidyl ether

The principal characteristics and products of thermal degradation of a commercial epoxy resin prepared by reaction of 2,2-bis(4′-hydroxy phenyl)propane (bisphenol-A) with 1-chloro-2,3-epoxy propane (epichlorhydrin) have been studied. The principal volatile products, acrolein, acetone and allyl alcohol, are formed at 280°C and, although cross-linking is detectable at 220°C, it only becomes significant at 320°C when the residual resin is brittle and insoluble. Decomposition of the cross-linked resin occurs above 340°C when phenolic compounds appear together with more complex products with higher molecular weights whose structures have been speculated upon from examination of their mass spectral characteristics.     

Degradation of epoxy polymers: 2—Mechanism of thermal degradation of bisphenol-A diglycidyl ether

In a previous paper, some 15 compounds were positively identified among the products of thermal degradation of bisphenol-A diglycidyl ether. The structures of an additional 22 compounds, all aromatic, were speculated upon on the basis of mass spectral analysis. In the present paper, mechanisms are proposed to account for all these products and the characteristics of their formation in the overall degradation process.     

Synthesis and 1H NMR study of 3,4-di ethyl-1,2,3,3a,4,5-hexahydro-canthinone-6

The racemic mixtures of the two epimers of 3,4-diethyl-l,2,3,3a,4,5-hexahydro-canthinone-6 (3,4-diethyl-2,3,3a,4,5,6-hexahydro-6-oxo-1H-indolo-(3,2,1 ,de) (1,5)naphtyridine) have been prepared. They were separated by crystallization of one of the synthesis intermediates. Identification of the configuration was possible by 1h NMR spectroscopy after running a 2D J-resolved spectrum of the “cis”-isomer.     

Development of a Chitosan/Nickel Phthalocyanine Composite Based Conductometric Micro-sensor for Methanol Detection

Thin-film composite of chitosan/nickel phthalocyanine (NiPc) was electrochemically deposited on the fingers of interdigitated gold electrodes, applying chronoamperometric polymerization technique. The presence of crystallized NiPc in the chitosan was confirmed by EDX and FTIR analysis. Acetone, ethanol, and methanol gas-sensing properties of the films prepared at optimum conditions were studied at atmospheric temperature, through differential measurements at an optimized frequency of 10 kHz, using a lock-in amplifier. The conductometric sensor presents the highest sensitivity of 60.2 μS.cm⁻¹(v/v) for methanol and 700 ppm as the limit of detection. For validation, the methanol content of a commercial rubbing alcohol was determined.     

Synthesis of Redox-Active Photochromic Phenanthrene Derivatives

A phenanthrene unit has been functionalized by several methylthiophene units in order to bring it a photochromic behavior. These compounds were characterized by NMR, absorption and emission spectroscopies, theoretical calculations as well as cyclic voltammetry. The association of a phenanthrene group with a photochromic center could open the door to a new generation of organic field-effect transistors.     

Detrimental Ni(0) transfer in Kumada catalyst transfer polycondensation of benzo[2,1‐b:3,4‐b']dithiophene

This article deals with the Kumada Catalyst Transfer Polycondensation (KCTP) of 4,7‐dioctylbenzo[2,1‐b:3,4‐b']dithiophene ( BDP‐Oct ) using Ni(II) catalyst or In/cat combination. A combination of MALDI MS, GPC, and ³¹P NMR spectroscopy is used to reveal the failure of the KCTP of this particular monomer. Intermolecular transfer reactions to monomer appeared to prevent the formation of polymer. This result is remarkable, since isomeric benzo[1,2‐b:4,5‐b']dithiophene polymerizes in a controlled way. The presence of a “non‐aromatic double bond” in annulated monomers is discussed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1706–1712     

Computational Fluid Dynamic Design of Jet Stirred Reactors for Measuring Intrinsic Kinetics of Gas‐Phase and Gas‐Solid Reactions

Nonreactive and reactive computational fluid dynamic simulations were applied to optimize the design of a laboratory scale jet stirred reactor for measuring intrinsic kinetics of gas‐phase and gas‐solid reactions, i.e. kinetics determined by chemical steps only and not by heat or mass transfer. In the past these reactors were designed and tested based on empirical design criteria and residence time distribution experiments. This work shows that these do not always capture important local effects that are vital for kinetic studies. First the degree of macro–mixing was evaluated for three different geometries (down case, 45° case and 90° case) by performing in silico residence time distribution experiments at 900 K, showing that with these type of experiments only minor differences are observed. However, the ethane steam cracking simulations revealed major differences, with the 45° case being the most uniform in terms of temperature and the 90° case being by far the worst. The species nonuniformity in all geometries was acceptable and was in some cases even partly masked by important shortcut streams such as those observed in the 90° case. The existing gradients on the substrate surface are sufficiently small to be neglected in modeling efforts. As temperature is the major parameter determining the rate of the surface reactions, the 45° case is suggested as the best geometry for measuring intrinsic kinetics.