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101.
Using controlled radical polymerization to confirm the lower critical solution temperature of an N‐(alkoxyalkyl) acrylamide polymer in aqueous solution 下载免费PDF全文
Xeniya Savelyeva Lucia Li Milan Marić 《Journal of polymer science. Part A, Polymer chemistry》2015,53(1):59-67
N‐(3‐Methoxypropyl) acrylamide (MPAM) was polymerized by controlled radical polymerization (CRP) methods such as nitroxide‐mediated polymerization (NMP) and reversible addition–fragmentation chain‐transfer polymerization (RAFT). CRP was expected to yield well‐defined polymers with sharp lower critical solution temperature (LCST) transitions. NMP with the BlocBuilder (2‐([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino]oxy)‐2‐methylpropanoic acid) and SG1 ([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino] oxidanyl) initiating system revealed low yields and lack of control (high dispersity, ? ~ 1.5–1.6, and inhibition of chain growth). However, RAFT was far more effective, with linear number average molecular weight, , versus conversion, X, plots, low ? ~ 1.2–1.4 and the ability to form block copolymers using N,N‐diethylacrylamide (DEAAM) as the second monomer. Poly(MPAM) (with = 13.7–25.3 kg mol?1) thermoresponsive behavior in aqueous media revealed cloud point temperatures (CPT)s between 73 and 92 °C depending on solution concentration (ranging from 1 to 3 wt %). The and the molecular weight distribution were the key factors determining the CPT and the sharpness of the response, respectively. Poly(MPAM)‐b‐poly(DEAAM) block copolymer ( = 22.3 kg mol?1, ? = 1.41, molar composition FDEAAM = 0.38) revealed dual LCSTs with both segments revealing distinctive CPTs (at 75 and 37 °C for poly(MPAM) and poly(DEAAM) blocks, respectively) by both UV–Vis and dynamic light scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 59–67 相似文献
102.
Current status of the TwinMic beamline at Elettra: a soft X‐ray transmission and emission microscopy station 下载免费PDF全文
Alessandra Gianoncelli George Kourousias Lucia Merolle Matteo Altissimo Anna Bianco 《Journal of synchrotron radiation》2016,23(6):1526-1537
The current status of the TwinMic beamline at Elettra synchrotron light source, that hosts the European twin X‐ray microscopy station, is reported. The X‐ray source, provided by a short hybrid undulator with source size and divergence intermediate between bending magnets and conventional undulators, is energy‐tailored using a collimated plane‐grating monochromator. The TwinMic spectromicroscopy experimental station combines scanning and full‐field imaging in a single instrument, with contrast modes such as absorption, differential phase, interference and darkfield. The implementation of coherent diffractive imaging modalities and ptychography is ongoing. Typically, scanning transmission X‐ray microscopy images are simultaneously collected in transmission and differential phase contrast and can be complemented by chemical and elemental analysis using across‐absorption‐edge imaging, X‐ray absorption near‐edge structure or low‐energy X‐ray fluorescence. The lateral resolutions depend on the particular imaging and contrast mode chosen. The TwinMic range of applications covers diverse research fields such as biology, biochemistry, medicine, pharmacology, environment, geochemistry, food, agriculture and materials science. They will be illustrated in the paper with representative results. 相似文献
103.
Organocatalytic,Asymmetric Eliminative [4+2] Cycloaddition of Allylidene Malononitriles with Enals: Rapid Entry to Cyclohexadiene‐Embedding Linear and Angular Polycycles 下载免费PDF全文
Dr. Nicoletta Brindani Dr. Gloria Rassu Dr. Luca Dell'Amico Dr. Vincenzo Zambrano Dr. Luigi Pinna Dr. Claudio Curti Dr. Andrea Sartori Prof. Dr. Lucia Battistini Prof. Dr. Giovanni Casiraghi Prof. Dr. Giorgio Pelosi Dr. Daniela Greco Prof. Dr. Franca Zanardi 《Angewandte Chemie (International ed. in English)》2015,54(25):7386-7390
A direct aminocatalytic synthesis has been developed for the chemo‐, regio‐, diastereo‐, and enantioselective construction of densely substituted polycyclic carbaldehydes containing fused cyclohexadiene rings. The chemistry utilizes, for the first time, remotely enolizable π‐extended allylidenemalononitriles as electron‐rich 1,3‐diene precursors in a direct eliminative [4+2] cycloaddition with both aromatic and aliphatic α,β‐unsaturated aldehydes. The generality of the process is demonstrated by approaching 6,6‐, 5,6‐, 7,6‐, 6,6,6‐, and 6,5,6‐fused ring systems, as well as biorelevant steroid‐like 6,6,6,6,5‐ and 6,6,6,5,6‐rings. A stepwise reaction mechanism for the key [4+2] addition is proposed as a domino bis‐vinylogous Michael/Michael/retro‐Michael reaction cascade. The utility of the malononitrile moiety as traceless activating group of the dicyano nucleophilic substrates is demonstrated. 相似文献
104.
Frank C. De Lucia Jr. Jennifer L. Gottfried Chase A. Munson Andrzej W. Miziolek 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1399-1404
Detecting trace explosive residues at standoff distances in real-time is a difficult problem. One method ideally suited for real-time standoff detection is laser-induced breakdown spectroscopy (LIBS). However, atmospheric oxygen and nitrogen contributes to the LIBS signal from the oxygen- and nitrogen-containing explosive compounds, complicating the discrimination of explosives from other organic materials. While bathing the sample in an inert gas will remove atmospheric oxygen and nitrogen interference, it cannot practically be applied for standoff LIBS. Alternatively, we have investigated the potential of double pulse LIBS to improve the discrimination of explosives by diminishing the contribution of atmospheric oxygen and nitrogen to the LIBS signal. These initial studies compare the close-contact (< 1 m) LIBS spectra of explosives using single pulse LIBS in argon with double pulse LIBS in atmosphere. We have demonstrated improved discrimination of an explosive and an organic interferent using double pulse LIBS to reduce the air entrained in the analytical plasma. 相似文献
105.
Sebastian Dresen Merja Gergov Lucia Politi Claudia Halter Wolfgang Weinmann 《Analytical and bioanalytical chemistry》2009,395(8):2521-2526
An electrospray ionization tandem mass spectrometry (ESI-MS/MS) library which contains over 5,600 spectra of 1,253 compounds
relevant in clinical and forensic toxicology has been developed using a hybrid tandem mass spectrometer with a linear ion
trap. Pure compound solutions—in some cases solutions made of tablets—were prepared and 1 to 2,000 ng of each compound were
injected into the system using standard reversed-phase analytical columns with gradient elution. To obtain maximum mass spectral
information enhanced product ion spectra were acquired with positive and/or negative ionization at low, medium, and high collision
energies and additionally applying collision energy spread. In this mode, all product ions generated by the different collision
energies are trapped in the linear ion trap prior to their detection. The applicability of the library for other types of
hybrid tandem mass spectrometers with a linear ion trap of the same manufacturer as well as a standard triple-quadrupole tandem
mass spectrometer has been investigated with a selection of compounds. The spectra of the developed library can be used to
create methods for target analysis, either screening methods or quantitative procedures by generating transitions for multiple
reaction monitoring. For those procedures, suitable transitions and convenient collision energies are selected from the library.
It also has been utilized to identify compounds with a multi target screening approach for clinical and forensic toxicology
with a standardized and automated system. The novel aspects compared to our former library produced with a standard triple-quadrupole
mass spectrometer are the enlargement of the ESI-MS/MS library and the additional acquisition of spectra with collision energy
spread. 相似文献
106.
Constable EC Handel RW Housecroft CE Farràn Morales A Ventura B Flamigni L Barigelletti F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(13):4024-4034
A new series of V-shaped trinuclear metallorods and X-shaped pentanuclear metallostars has been prepared by the reaction of metal complexes bearing pendant phenolic functionalities with complexes containing electrophilic ligands. Specifically, {M(tpy)2} motifs (M=Ru or Os; tpy=2,2':6',2'-terpyridine) bearing one or two pendant 3,5-dihydroxyphenyl substituents at the 4-position of the central ring of the tpy have been reacted with the complexes [Ru(tpy)(Xtpy)]2+ (X=Cl or Br) to form new ether-linked species. The energy transfer from ruthenium to osmium in these complexes has been investigated in detail and the efficiency of transfer shown to be highly temperature dependent; the energy transfer is highly efficient at low temperature, whereas at room temperature nonradiative and nontransfer deactivation of the excited {Ru(tpy)2}* domains is most significant. 相似文献
107.
Bartolo Gabriele Lucia Veltri Pierluigi Plastina Mirco Costa 《Tetrahedron letters》2010,51(13):1663-1786
A novel and convenient approach to furan-3-carboxylic esters 2 is presented, based on palladium-catalyzed direct oxidative carbonylation of readily available 3-yne-1,2-diols 1. The process, corresponding to a sequential combination between a 5-endo-dig heterocyclodehydration step and an oxidative alkoxycarbonylation stage, is catalyzed by PdI2 in conjunction with an excess of KI under relatively mild conditions (100 °C in ROH under 40 atm of a 4:1 mixture of CO-air). 相似文献
108.
In this paper, we propose a mathematical model with time delay to describe the process of diffusion of a new technology. This model is suitable for modeling diffusion processes of all those technologies that require great initial investments and public subsidies, such as technologies used for producing renewable energy. We consider external factors, such as the government policy and the production costs, that influence the decision of adoption of the new technology. We also consider the internal influence from adopters. The adoption process is described by a delay differential equation. The time delay represents the evaluation stage at which the potential consumers decide whether to adopt the new technology or not. A qualitative analysis is carried out in order to assess the stability of the equilibrium for certain parameters and to find the final level of adopters. 相似文献
109.
Braga D Maini L Polito M Mirolo L Grepioni F 《Chemical communications (Cambridge, England)》2002,(24):2960-2961
Solvent-free reactions with molecular systems have been exploited to prepare hybrid organic-organometallic solids: grinding of the complex [Fe(eta 5-C5H4COOH)2] with solid bases B generates quantitatively the corresponding hydrogen bonded salts [Fe(eta 5-C5H4COOH)(eta 5-C5H4COO)][HB] (B = 1,4-diazabicyclo[2.2.2]octane, 1,4-phenylenediamine); gas-solid reactions are also possible with volatile bases. 相似文献
110.
Hans-Jürgen?BuschmannEmail author Lucia?Mutihac Eckhard?Schollmeyer 《Journal of inclusion phenomena and macrocyclic chemistry》2005,51(1-2):53-57
The formation of complexes between α-cyclodextrin and n-alkylamines and their hydrochlorides has been studied in aqueous solution using calorimetric titrations. All alkylamines form stronger complexes than the corresponding hydrochlorides. The values of the reaction enthalpies are smaller for the alkylamine hydrochlorides compared with the alkylamines. By increasing the number of methylene groups, these differences become smaller. In addition, the reaction enthalpies for protonation of the alkylamines and their complexes with α-cyclodextrin have been measured. The heat of protonation of these complexes is always smaller compared with the alkylamines. Due to the protonation and the formation of a strong solvation shell around the ammonium group the interactions with α-cyclodextrins are weakened. From a thermodynamic cycle using all measured reactions, it can be concluded that the aggregation of the alkylamines with long alkyl chains (heptyl-, octyl-, and nonylamine) has an influence on the values of the reaction enthalpies and entropies for the protonated form only.This revised version was published online in July 2005 with a corrected issue number. 相似文献