Isobutylene‐rich macromonomers: Dynamics and yields of peroxide‐initiated crosslinking

New isobutylene‐rich elastomers bearing multiple pendant styrenic, acrylic, maleimidic, vinylic, and allylic functional groups have been prepared and examined in the context of peroxide‐initiated crosslinking. Halide displacement from brominated poly(isobutylene‐co‐isoprene) (BIIR) by the requisite carboxylate nucleophiles in homogeneous toluene solutions provide the desired esters in quantitative yield without complications from dehydrohalogenation or premature crosslinking. Heating the resulting macromonomers with dicumyl peroxide to 160 °C under solvent‐free conditions gives thermoset derivatives, with reaction rates and yields depending markedly on functional group structure. In general, high cure extents can only be achieved using highly reactive pendant functional groups, owing to the competitive balance between crosslinking through C?C oligomerization, and degradation through β‐scission of backbone macroradical intermediates. Independent control of crosslinking rates and cure extents is gained through the use of nitroxyl radical traps bearing acrylate functionality. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 123–132     

Spectral deep learning for prediction and prospective validation of functional groups

State-of-the-art identification of the functional groups present in an unknown chemical entity requires the expertise of a skilled spectroscopist to analyse and interpret Fourier transform infra-red (FTIR), mass spectroscopy (MS) and/or nuclear magnetic resonance (NMR) data. This process can be time-consuming and error-prone, especially for complex chemical entities that are poorly characterised in the literature, or inefficient to use with synthetic robots producing molecules at an accelerated rate. Herein, we introduce a fast, multi-label deep neural network for accurately identifying all the functional groups of unknown compounds using a combination of FTIR and MS spectra. We do not use any database, pre-established rules, procedures, or peak-matching methods. Our trained neural network reveals patterns typically used by human chemists to identify standard groups. Finally, we experimentally validated our neural network, trained on single compounds, to predict functional groups in compound mixtures. Our methodology showcases practical utility for future use in autonomous analytical detection.

A new multi-label deep neural network architecture is used to combine Infrared and mass spectra, trained on single compounds to predict functional groups, and experimentally validated on complex mixtures.     

Development and validation of a sensitive and high‐throughput LC‐MS/MS method for the simultaneous determination of esomeprazole and naproxen in human plasma

A sensitive and high‐throughput LC‐MS/MS method has been developed and validated for the combined determination of esomeprazole and naproxen in human plasma with ibuprofen as internal standard. Solid‐phase extraction was used to extract both analytes and internal standard from human plasma. Chromatographic separation was achieved in 4.0 min on XBridge C₁₈ column using acetonitrile–25 mM ammonium formate (70:30, v/v) as mobile phase. Mass detection was achieved by ESI/MS/MS in negative ion mode, monitoring at m/z 344.19 → 194.12, 229.12 → 169.05 and 205.13 → 161.07 for esomeprazole, naproxen and IS, respectively. The calibration curves were linear from 3.00 to 700.02 ng/mL for esomeprazole and 0.50 to 150.08 ng/mL for naproxen. The intra‐ and inter‐batch precision and accuracy across four quality control levels met established criteria of US Food and Drug Administration guidelines. The assay is suitable for measuring accurate esomeprazole and naproxen plasma concentrations in human bioequivalence study following combined administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Mixed convection in non-Newtonian fluids along nonisothermal horizontal surfaces in porous media

A nonsimilar boundary layer analysis is presented for the problem of mixed convection in power-law type non-Newtonian fluids along horizontal surfaces with variable wall temperature distribution. The mixed convection regime is divided into two regions, namely, the forced convection dominated regime and the free convection dominated regime. The two solutions are matched. Numerical results are presented for the details of the velocity and temperature fields. A discussion is provided for the effect of viscosity index on the surface heat transfer rate. Received on 11 March 1997     

Nonsimilar Solutions for Mixed Convection in Non-Newtonian Fluids Along Horizontal Surfaces in Porous Media

A nonsimilar boundary layer analysis is presented for the problem of mixed convection in power-law type non-Newtonian fluids along horizontal surfaces with variable heat flux distribution. The mixed convection regime is divided into two regions, namely, the forced convection dominated regime and the free convection dominated regime. The two solutions are matched. Numerical results are presented for the details of the velocity and temperature fields. A discussion is provided for the effect of viscosity index on the surface heat transfer rate.     

Optical,thermal and mechanical characterization of Al(III)/Sb(III)-doped tris(thiourea)zinc(II) sulphate crystals

The influence of Al(III)/Sb(III)-doping on the properties of tris(thiourea)zinc(II) sulphate (ZTS) crystals grown by slow evaporation solution growth technique is reported. The as-grown crystals belong to orthorhombic system and cell parameters are, a = 7.77 Å, b = 11.13 Å, c = 15.47 Å, V = 1338 Å³ (Al(III)-doped) and a = 11.1996 Å, b = 7.770 Å, c = 15.5598 Å, V = 1368.3 Å³ (Sb(III)-doped). The structure and the crystallinity of the materials are further confirmed by powder X-ray diffraction analysis. The modes of vibrations of different functional groups present are identified by Fourier transform infrared studies. Thermogravimetric/differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. Surface morphological changes due to doping are observed by scanning electron microscopy. Microhardness study was carried out to elucidate the mechanistic behavior microhardness studies were carried out to elucidate the mechanistic behavior. Second harmonic generation activity is much better in the case of Sb(III)-doping. The specimen is also characterized by dielectric studies.     

Octahedral oligomeric silsesquioxane (OAPS and OG) - Polyimide hybrid nanocomposite films: Thermo-mechanical,dielectric and morphology properties

Abstract

The nano-sized SQS based polyimides have been successfully synthesized with different oxide groups such as phosphineoxide, sulfone and siloxane as in the backbone of polymer. The SQS-Polyimide nanocomposites prepared through the condensation process using amine and epoxy functionalized SQS as precursor. The presence of SQS in the resulting polyimide nanocomposites was confirmed by FTIR and XRD analyses. The presence of SQS and greatly enhances the char yield to an extent of 16% when compared to that of neat polyimide. The incorporation of SQS into polyimide lowered the value of dielectric constant from 3.31 to 2.09 at 1?MHz and the value of thermal expansion coefficient from 56.6 to 42.7?ppm/K. The composites sample prepared using 20?wt% SQS possess the lowest value of dielectric constant and CTE value. The hydrophobic nature of SQS contributes to lower the water uptake of composites from a value of 2.76 (neat polyimide) to 2.42 for POS-PI containing 20?wt% SQS. Further, the SQS polyimide composite systems possess the enhanced values of thermal stability and glass transition temperatures according their percentage weight. Data obtained from different studies, it is suggested that these hybrid composites can be used as an effective insulation materials for high performance microelectronics applications.