Microstructural study of a nitroxide-mediated poly(ethylene oxide)/polystyrene block copolymer (PEO- b PS) by electrospray tandem mass spectrometry (original) (raw)
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Rapid Communications in Mass Spectrometry, 2009
Different cationic adducts of poly(ethylene oxide)/polystyrene block co-oligomers could be produced by adjusting the salt concentration in the mobile phase using a coupling between liquid chromatography at critical conditions and electrospray ionization mass spectrometry. Formation of doubly lithiated adducts was observed at high LiCl concentration (1 mM) while lowering the salt concentration down to 0.1 mM allowed co-oligomers to be ionized with both a proton and a lithium. The fragmentation pathways observed to occur upon collision-induced dissociation of ionized copolymers were shown to be highly dependent on the nature of the cationic adducts. As a result, complementary structural information could be reached by performing MS/MS experiments on different ionic forms of the same co-oligomer molecule. On one hand, release of the nitroxide end-group as a radical from [M+2Li]2+ was followed by a complete depolymerization of the polystyrene block, allowing both this end-group and the polystyrene segment size to be determined. On the other hand, [M+H+Li]2+ precursor ions mainly dissociated via reactions involving bond cleavages within the nitroxide moiety, yielding useful structural information on this end-group. Copyright © 2009 John Wiley & Sons, Ltd.
Macromolecules, 2012
Separation of functional poly(ethylene oxide) PEO and PEO block copolymers was investigated using liquid chromatography under critical conditions (LCCC) with a mixture of organic solvents as eluent. The optimum eluent is a mixture of 58.05% chloroform, 6.45% methanol, and 35.50% n-heptane (v/v/v) using a reverse phase (C 8) column. Unlike what was expected, the elution mechanism is governed by the interaction of a polar endgroup with the column. In these conditions, poly(ethylene oxide) (PEO) functionalized with either an acrylate or alkoxyamine moieties were separated. This allows us to investigate the efficiency of the synthesis of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) and polystyrene-b-poly(ethylene oxide) b-polystyrene (PS-b-PEO-b-PS) block copolymers prepared via the combination of 1,2 radical intermolecular addition followed by the nitroxide-mediated polymerization NMP of styrene. Amphiphilic diblock PEO-b-PS and triblock PS-b-PEO-b-PS copolymers were also separated from PEO homopolymers using the same experimental conditions. We showed that the PEO block is then invisible, and the calibration curve obtained using PS homopolymer standards could be used to determine the whole molar mass of the PS block in block copolymers with PS and PEO segments, with a weak influence of the architecture.
Rapid Communications in Mass Spectrometry, 1998
A poly(amino)ester dendrimer, bearing tert-butyl ester terminations and used as the precursor of an acid-terminating poly(amino)ester dendrimer, was studied by electrospray ionization tandem mass spectrometry to establish its fragmentation rules upon collision-induced dissociation. Mechanisms for dissociation reactions experienced by protonated molecules were proposed and supported by accurate mass measurements. The release of 2-methylprop-1-ene was observed as many times as tert-butyl groups were available. Each of these steps was followed by elimination of carbon dioxide and ethylene within the so-deprotected branches. Detachment of an entire arm, released as a neutral or as a protonated molecule, was found to be a useful complementary process but it mainly proceeded from the singly charged precursor. Three targeted dendritic impurities were structurally characterized by monitoring the occurrence of these reactions together with any deviation from the reference behavior. Detection of these compounds in the precursor sample could account for the presence of defective molecules previously characterized in the acid-terminating poly(amino)ester dendrimer sample.
N+ion–target interactions in PPO polymer: A structural characterization
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1999
N ion beam induced eects on the spin coated amorphous poly(2,6-dimethyl phenylene oxide) (PPO) ®lms in terms of chemical structure and electronic and vibrational properties were investigated using Fourier Transform Infrared spectroscopy (FTIR) and Ultraviolet±Visible (UV±VIS) spectroscopy. Both techniques revealed that the stability of PPO was very weak towards 100 keV N ions revealing the threshold¯uence to be 10 14 ions/cm 2 for fragmentation of the polymer. FTIR analysis showed disappearance of all characteristic IR bands at a total¯uence of 10 14 ions/cm 2 except for the band C¸C at 1608 cm À1 which was found to shift to a lower wave number along with an enhancement in the full width half maximum (FWHM) value with increasing¯uence. A new bond appeared due to oxidation as a shoulder at 1680 cm À1 in FTIR spectra indicating the presence of C¸O type bond as a result of N implantation on PPO ®lms. The optical band gap (E g) deduced from absorption spectra, was observed to decrease from 4.4 to 0.5 eV with¯uence. The implantation induced carbonaceous clusters, determined using RobertsonÕs formula for the optical band gap, were found to consist of $160 fused hexagonal aromatic rings at the maximum energy¯uence. An enhanced absorption coecient as a function of¯uence indicated incorporation of either much larger concentration of charge carriers or their mobility than that of the pristine sample. Calculated band tail width from Urbach band tail region for the implanted samples pointed the band edge sharpness to be strongly dependent on¯uence indicating an increased disorder with increasing¯uence.
Macromolecules, 2008
The strategy developed in this report consisted of synthesizing polystyrene (PS) blocks by nitroxidemediated controlled radical polymerization from poly(ethylene oxide) (PEO) macroinitiators. Difunctional macroinitiators were first prepared in a two-step procedure by reacting PEO (M n ranging from 1450 to 35000 g/mol) with MONAMS, an alkoxyamine based on N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)nitroxide, called SG1. A series of polystyrene-block-poly(ethylene oxide)-block-polystyrene (PS-b-PEO-b-PS) triblock copolymers was then synthesized with various chain dimensions and PEO block mass fractions from 0.13 to 0.65. Precise insight into the prepared triblock copolymer structure in terms of molecular weight, block length, and polydispersity index was obtained using complementary characterization techniques such as 1 H NMR spectroscopy and size exclusion chromatography (SEC). These data were completed by two-dimensional chromatography, a combination of liquid chromatography at the critical conditions and SEC, to check purity (homo-PS formation) and composition homogeneity. Well-defined PS-b-PEO-b-PS triblock copolymers having a large range of chain dimensions (M n of block copolymers ranging from 5000 to 200000 g/mol) and block lengths (M n of PS blocks between 2000 and 83000 g/mol) with a low polydispersity index (1.1-1.3) were prepared using this new route.
Journal of Polymer Science Part B: Polymer Physics, 2010
The microphase structure of a series of polystyrene-bpolyethylene oxide-b-polystyrene (SEOS) triblock copolymers with different compositions and molecular weights has been studied by solid-state NMR, DSC, wide and small angle X-ray scattering (WAXS and SAXS). WAXS and DSC measurements were used to detect the presence of crystalline domains of polyethyleneoxide (PEO) blocks at room temperature as a function of the copolymer chemical composition. Furthermore, DSC experiments allowed the determination of the melting temperatures of the crystalline part of the PEO blocks. SAXS measurements, performed above and below the melting temperature of the PEO blocks, revealed the formation of periodic structures, but the absence or the weakness of high order reflections peaks did not allow a clear assessment of the morphological structure of the copolymers. This information was inferred by combining the results obtained by SAXS and 1 H NMR spin diffusion experiments, which also provided an estimation of the size of the dispersed phases of the nanostructured copolymers. V C 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 55-64, 2010
European Polymer Journal, 1977
Conductivity studies were carried out on block copolymers of composition K +, -(EO),-~MeSt-(St)~-~MeSt-(EO)~-, K +, where n = 1-5 or 20, in THF. The conductivity of the solutions exhibits a strong tendency to increase as n is raised up to 3, and to change only slightly on further extension of the polyether chain. An equilibrium between ion pairs and free ions is established in the solution only when n is 1 or 2; for n >/3, ion triplets are formed also. The dissociation constants for the ion pairs and the ion triplets and their temperature dependence were determined. The formation of ion triplets, as well as the changes in dissociation of the ion species on extending the polyether block, are explained by solvation of the counter-ion by the polyether chain.
Journal of Polymer Science Part A-polymer Chemistry, 2005
Amphiphilic poly(ethylene oxide)-block-poly(isoprene) (PEO-b-PI) diblock copolymers were prepared by nitroxide-mediated polymerization of isoprene from alkoxyamine-terminal poly(ethylene oxide) (PEO). PEO monomethyl ether (Mn ≈ 5200 g/mol) was functionalized by esterification with 2-bromopropionyl bromide with subsequent copper-mediated replacement of the terminal bromine with 2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide. The resulting PEO-alkoxyamine macroinitiator was used to initiate polymerization of isoprene in bulk and in solution at 125 °C to yield PEO-b-PI block copolymers with narrow molecular weight distributions (Mw/Mn ≤ 1.1). Polymerizations were first order in isoprene through 35% conversion. Micellar aggregates of PEO-b-PI in aqueous solution were crosslinked by treatment with a water-soluble redox initiating system, and persistent micellar structures were observed in the dry state by AFM. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2977–2984, 2005