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11.
A facile synthesis of catechol‐functionalized poly(ethylene oxide) block and random copolymers 下载免费PDF全文
Kaila M. Mattson Allegra A. Latimer Alaina J. McGrath Nathaniel A. Lynd Pontus Lundberg Zachary M. Hudson Craig J. Hawker 《Journal of polymer science. Part A, Polymer chemistry》2015,53(23):2685-2692
Herein we develop a facile synthetic strategy for the functionalization of well‐defined polyether copolymers with control over the number and location of catechol groups. Previously, the functionalization of polyethylene oxide (PEO)‐based polymers with catechols has been limited to functionalization of the chain ends only, hampering the synthesis of adhesive and antifouling materials based on this platform. To address this challenge, we describe an efficient and high‐yielding route to catechol‐functionalized polyethers, which could allow the effects of polymer architecture, molecular weight, and catechol incorporation on the adhesive properties of surface‐anchored PEO to be studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2685–2692 相似文献
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Hojjatie MM Abrams DE Parham TM Balthrop J Beine R Dickinson V Hartshorn J Herald S Latimer G Padmore J Pleasants S Riter K Roser R Schmunck G Sensmeier R Smith V Taylor L Volgas G 《Journal of AOAC International》2004,87(2):346-351
Water soluble urea-formaldehyde (UF) fertilizers, manufactured by complex reaction of urea and formaldehyde, typically contain varying amounts of unreacted urea. A liquid chromatography method for the analysis of urea in these products, and in aqueous urea solutions, was collaboratively studied. An amine chromatography column was used to separate the unreacted urea from numerous UF reaction products present in these liquid fertilizers. Unreacted urea was determined by using external urea standards with UV detection at 195 nm. The standards and test samples were prepared in the mobile phase of 85% (v/v) acetonitrile in water. Ten laboratories analyzed 5 different UF-based commercial products containing unreacted urea in the range of 6 to 17% by weight, and 5 different concentrations of urea in water equivalent to commercial products of that nature. The aqueous urea solutions contained 2-20% urea (w/w). The range of s(R) values for the 5 UF-based commercial fertilizers was 0.49-1.02 and the %RSD(R) was 1.94-6.14. The s(R) range for the 5 urea solutions was 0.10 to 0.79 and the %RSD(R) range was 2.54 to 4.88. The average recovery of urea from the aqueous urea solutions was 96-103%. Therefore, this method is capable of monitoring urea nitrogen manufacturers' label claims and total nitrogen claims in those cases where urea is the sole source of plant food nitrogen. Based on the collaborative study data, the authors recommend this method be approved for AOAC Official First Action status. 相似文献
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Revisiting thiol-yne chemistry: Selective and efficient monoaddition for block and graft copolymer formation 下载免费PDF全文
Johannes K. Sprafke Jason M. Spruell Kaila M. Mattson Damien Montarnal Alaina J. McGrath Robert Pötzsch Daigo Miyajima Jerry Hu Allegra A. Latimer Brigitte I. Voit Takuzo Aida Craig J. Hawker 《Journal of polymer science. Part A, Polymer chemistry》2015,53(2):319-326
The untapped potential of radical thiol-yne mono-addition chemistry is exploited to overcome the known limitations of thiol-ene chemistry in polymer coupling and block copolymer formation. By careful choice of alkyne, the reaction can selectively lead to the mono-addition product with efficiencies surpassing those achieved by traditional thiol-ene chemistry. This improvement is illustrated by the nearly quantitative synthesis of a variety of diblock and graft copolymers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 319–326 相似文献
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Ethylenediaminetetra-acetic acid (EDTA) and nitrilotri-acetic acid (NTA) can be differentiated and determined by titration with metal ions to visual metallochromic dye end-points. EDTA can be determined without interference from NTA, either by titrating with copper(II) at pH 5 using PAN indicator, or by titrating with iron(III) at pH 6 and 70 degrees using Tiron indicator. The total chelating power (EDTA + NTA) can be determined either by titrating with lead(II) at pH 4.4 using dithizone indicator, or by titrating with iron(III) at pH 3.5 using Tiron indicator ; NTA is determined by difference. The lowest concentration at which NTA can be determined in EDTA by titration to the iron(III)-Tiron end-point is about 1 wt.%. The apparent stability constants of the iron(III)-Tiron complexes under the conditions of the titration at pH 3.5 and pH 6 have been determined using the method of continuous variations. 相似文献
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Thomas Boucher CJ Carey Melinda Darby Dyar Sridhar Mahadevan Samuel Clegg Roger Wiens 《Journal of Chemometrics》2015,29(9):484-491
Laser‐induced breakdown spectroscopy (LIBS) is currently being used onboard the Mars Science Laboratory rover Curiosity to predict elemental abundances in dust, rocks, and soils using a partial least squares regression model developed by the ChemCam team. Accuracy of that model is constrained by the number of samples needed in the calibration, which grows exponentially with the dimensionality of the data, a phenomenon known as the curse of dimensionality. LIBS data are very high dimensional, and the number of ground‐truth samples (i.e., standards) recorded with the ChemCam before departing for Mars was small compared with the dimensionality, so strategies to optimize prediction accuracy are needed. In this study, we first use an existing machine learning algorithm, locally linear embedding (LLE), to combat the curse of dimensionality by embedding the data into a low‐dimensional manifold subspace before regressing. LLE constructs its embedding by maintaining local neighborhood distances and discarding large global geodesic distances between samples, in an attempt to preserve the underlying geometric structure of the data. We also introduce a novel supervised version, LLE for regression (LLER), which takes into account the known chemical composition of the training data when embedding. LLER is shown to outperform traditional LLE when predicting most major elements. We show the effectiveness of both algorithms using three different LIBS datasets recorded under Mars‐like conditions. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Gon Namkoong Patrick Boland Si‐Young Bae Jae‐Phil Shim Dong‐Seon Lee Seong‐Ran Jeon Kurniawan Foe Kevin Latimer W. Alan Doolittle 《固体物理学:研究快报》2011,5(2):86-88
We performed detailed studies of the effect of polarization on III‐nitride solar cells. Spontaneous and piezoelectric polarizations were assessed to determine their impacts upon the open circuit voltages (VOC) in p–i(InGaN)–n and multi‐quantum well (MQW) solar cells. We found that the spontaneous polarization in Ga‐polar p–i–n solar cells strongly modifies energy band structures and corresponding electric fields in a way that degrades VOC compared to non‐polar p–i–n structures. In contrast, we found that piezoelectric polarization in Ga‐polar MQW structures does not have a large influence on VOC compared to non‐polar MQW structures. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The absorption characteristics of elastic framed absorbers in combination with impervious films has been investigated. The effect of bonding the film to the absorber and the absorbers to their rear surface was examined. The results have been modelled using established methods for predicting the absorption of elastic framed porous materials. The absorption of a foam with a film bonded to its top surface was most sensitive to the rear surface bonding condition. Plain foams and foams with loose-laid surface films were less sensitive to the rear surface bonding condition. The results demonstrate that test data used to predict absorption performance need to reflect the absorber mounting conditions. 相似文献