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81.
Lin W Ma X Qian J Abdelrahman AI Halupa A Baranov V Pich A Winnik MA 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):7265-7275
This article describes the synthesis and characterization of two series of functional polyelectrolyte copolymer microgels intended for bioassays based upon mass cytometry, a technique that detects metals by inductively coupled plasma mass spectrometry (ICP-MS). The microgels were loaded with Eu(III) ions, which were then converted in situ to EuF(3) nanoparticles (NPs). Both types of microgels are based upon copolymers of N-isopropylacrylamide (NIPAm) and methacrylic acid (MAA), poly(NIPAm/VCL/MAA) (VCL = N-vinylcaprolactam, V series), and poly(NIPAm/MAA/PEGMA) (PEGMA = poly(ethylene glycol)methacrylate, PG series). Very specific conditions (full neutralization of the MAA groups) were required to confine the EuF(3) NPs to the core of the microgels. We used mass cytometry to measure the number and the particle-to-particle variation of Eu ions per microgel. By controlling the amount of EuCl(3) added to the neutralized microgels. we could vary the atomic content of individual microgels from ca. 10(6) to 10(7) Eu atoms, either in the form of Eu(3+) ions or EuF(3) NPs. Leaching profiles of Eu ions from the hybrid microgels were measured by traditional ICP-MS. 相似文献
82.
P Cao L Tong Y Hou G Zhao G Guerin MA Winnik M Nitz 《Langmuir : the ACS journal of surfaces and colloids》2012,28(35):12861-12870
The range of properties available in the lanthanide series has inspired research into the use of lanthanide nanoparticles for numerous applications. We aim to use NaLnF(4) nanoparticles for isotopic tags in mass cytometry. This application requires nanoparticles of narrow size distribution, diameters preferably less than 15 nm, and robust surface chemistry to avoid nonspecific interactions and to facilitate bioconjugation. Nanoparticles (NaHoF(4), NaEuF(4), NaGdF(4), and NaTbF(4)) were synthesized with diameters from 9 to 11 nm with oleic acid surface stabilization. The surface ligands were replaced by a series of mono-, di-, and tetraphosphonate PEG ligands, whose synthesis is reported here. The colloidal stability of the resulting particles was monitored over a range of pH values and in phosphate containing solutions. All of the PEG-phosphonate ligands were found to produce non-aggregated colloidally stable suspensions of the nanoparticles in water as judged by DLS and TEM measurements. However, in more aggressive solutions, at high pH and in phosphate buffers, the mono- and diphosphonate PEG ligands did not stabilize the particles and aggregation as well as flocculation was observed. However, the tetraphosphonate ligand was able to stabilize the particles at high pH and in phosphate buffers for extended periods of time. 相似文献
83.
If two good solvents become poor for a polymer when mixed, the solvent pair is called a cononsolvent pair. The sharp reentrant coil-to-globule-to-coil transition of a poly(N-isopropylacrylamide) chain observed in the mixed solvent of water and methanol is shown to be caused by the competitive hydrogen bonding by water and methanol molecules onto the polymer chain. On the basis of a new statistical-mechanical model for competitive hydrogen bonds, the mean square end-to-end distance is theoretically calculated and compared with experiment. The chain sharply collapses at the molar fraction xm approximately 0.2 of methanol, stays collapsed up to xm approximately 0.4, and finally recovers the swollen state at xm approximately 0.6. Such a reentrant coil-globule transition takes place because the total number of hydrogen bonds along the chain exhibits a similar square-well-type depression as a result of the competition. 相似文献
84.
Sébastien Gouin M. Victoria Valencia Grayeb Françoise M. Winnik 《Macromolecular Symposia》2002,186(1):105-110
We have prepared new hyaluronan (HA) gadolinium diethylenetriaminepentaacetic acid (DTPA) conjugates that have potential as tumor specific contrast agents for magnetic resonance imaging. Conjugates were synthesized, starting with a high molecular weight HA or with HA oligomers, by an efficient 2-step procedure involving first, reaction of ethylenediamine with HA carboxylic acid groups and, second, covalent linkage of DTPA to aminated HA. The final polymers were compared in terms of molar masses and DTPA content. Tapping mode atomic force microscopy has been used to examine the morphology of the polymers in aqueous solution. 相似文献
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88.
Roger W. Binkley Glen W. Dillow Thomas W. Flechtner Witold Winnik Michael J. S. Tevesz 《Journal of mass spectrometry : JMS》1994,29(9):491-495
Low-energy collisionally activated dissociation of O-deprotonated dihydroxybenzenes (catechol, resorcinol, hydroquinone) in the gas phase causes both fragmentation to form [C6H4O2]– ions by loss of the remaining oxygen-bound hydrogen atom and intramolecular hydrogen atom migration from O to C. The rearranged anions then undergo ring-cleavage reactions which are different in each case. Both catechol and hydroquinone produce fragments which are the result of the loss of two carbon atoms and both oxygen atoms but the proposed mechanisms are different. Resorcinol also produces a fragment which derives from the loss of carbon dioxide. For this process a mechanism is proposed which involves a 6-methylpyranone anion intermediate. 相似文献
89.
Jung Kwon Oh Jun Wu Mitchell A. Winnik Gary P. Craun Jude Rademacher Rajeev Farwaha 《Journal of polymer science. Part A, Polymer chemistry》2002,40(10):1594-1607
This article describes our first experiments for preparing dye‐labeled latex particles by the emulsion copolymerization of a 4/1 (w/w) mixture of vinyl acetate‐butylacrylate (VAc‐BA). We discuss the synthesis of acrylate derivatives of phenanthrene, anthracene, and pyrene [9‐acryloxymethyl phenanthrene ( 7 ), 9‐acryloxymethyl‐10‐methyl anthracene ( 8 ), and 1‐acryloxymethyl pyrene ( 10 )] and an allyl ether derivative of anthracene [9‐allyoxymethyl‐10‐methyl anthracene ( 9 )]. Although the phenanthrene derivative 7 gave latex particles with high monomer conversion and good dye incorporation, the pyrene acrylate and both anthracene comonomers strongly inhibited the free‐radical reaction. To assist our search for a dye that would serve as a useful energy acceptor for phenanthrene and without suppressing VAc‐BA polymerization, we also examined batch emulsion polymerization in the presence of a variety of dye derivatives—substituted anthracenes, acridines, a coumarin, and two benzophenone derivatives. All of the anthracene derivatives, as well as acridine, strongly inhibited monomer polymerization. The coumarin dye 7‐hydroxy‐4‐methyl coumarin ( 22 ) that had only limited solubility allowed more than 90% monomer conversion. Most promising were 2‐hydroxy‐5‐methyl benzophenone ( 23 ) and 4‐N,N‐dimethylamino benzophenone ( 24 ) that at 1 mol % in the monomer mixture permitted virtually quantitative monomer conversion to latex. 4′‐Dimethylamino‐2‐acryloxy‐5‐methyl benzophenone ( 25 ) copolymerized well with the VAc‐BA mixture, yielding latex particles in high yield and with a narrow size distribution. These dyes appear to be useful acceptor dyes for energy‐transfer experiments with phenanthrene. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1594–1607, 2002 相似文献
90.
Raez J Zhang Y Cao L Petrov S Erlacher K Wiesner U Manners I Winnik MA 《Journal of the American Chemical Society》2003,125(20):6010-6011
We report that an asymmetric diblock copolymer, poly(ferrocenyldimethylsilane-b-dimethylsiloxane) (PFS90-b-PDMS900, PDI = 1.01, volume fraction PFS = 0.20), self-assembles in the bulk state to form a hexagonal periodic structure with a remarkable morphology. Part of the major component forms the core of concentric cylinders with a mean diameter of 35.5 nm surrounded by a 7 nm thick shell of PFS. The remaining PDMS fills the interstitial spaces. The morphology was elucidated by small-angle X-ray scattering, as well as by scanning and conventional transmission electron microscopy. 相似文献