Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (178)
- Vortrag (12)
- Beitrag zu einem Sammelband (9)
- Beitrag zu einem Tagungsband (8)
- Posterpräsentation (7)
- Buchkapitel (2)
Sprache
- Englisch (216) (entfernen)
Schlagworte
- MALDI-TOF MS (62)
- Polylactide (45)
- Cyclization (27)
- MALDI (20)
- Ring-opening polymerization (17)
- Polycondensation (15)
- MALDI TOF MS (10)
- Mass spectrometry (9)
- Pollen (8)
- Polymerization (8)
- Transesterification (8)
- Crystallization (7)
- Polymers (7)
- Ring-expansion polymerization (7)
- Catalyst (6)
- Crystalinity (6)
- Ionization (6)
- Polymere (6)
- Catalysts (5)
- Isosorbide (5)
- Lactide (5)
- Polyester (5)
- MALDI Massenspektrometrie (4)
- MALDI-TOF mass spectrometry (4)
- Polyesters (4)
- Polyglycolide (4)
- Polylactides (4)
- Ring opening polymerization (4)
- Biobased polymers (3)
- Bismuth (3)
- Cyclic (3)
- ICP-MS (3)
- Imaging (3)
- Liquid chromatography (3)
- Multivariate statistics (3)
- Polymer (3)
- Polymerisation (3)
- ROPPOC (3)
- SEC (3)
- Silver nanoparticles (3)
- Small-angle X-ray scattering (3)
- Adsorption (2)
- Amphiphiles (2)
- Annealing (2)
- Biodegradable (2)
- Blends (2)
- Block copolymers (2)
- Catechol (2)
- Chromatographie (2)
- Chromatography (2)
- Conductive carbon tape (2)
- Coupling methods (2)
- Crosslinking (2)
- Crystals (2)
- Cyclopolymerization (2)
- Dispersity (2)
- ESI (2)
- Electrospray ionization (2)
- Epsilon-caprolactone (2)
- FTIR (2)
- Field-flow fractionation (2)
- Isotope dilution analysis (2)
- Kopplung (2)
- Liquid adsorption chromatography (2)
- MALDI mass spectrometry (2)
- MALDI-TOF-MS (2)
- MS/MS (2)
- Macrocycles (2)
- Massenspektrometrie (2)
- Matrix-assisted laser desorption/ionization (2)
- Plasma modification (2)
- Polystyrene (2)
- Polyurethane (2)
- Polyurethanes (2)
- Principal component analysis (2)
- Reversible addition fragmentation chain transfer (RAFT) (2)
- Ring-opening Polymerization (2)
- SAXS (2)
- Sample preparation (2)
- Sample pretreatment (2)
- Synthesis (2)
- Thermal degradation (2)
- Tin acetates (2)
- Tin catalysts (2)
- 2-oxazoline (1)
- A4F (1)
- AET (1)
- AFM (1)
- Adhesion promoting interlayers (1)
- Adhesion promotion (1)
- Alternating co-poly(ether pyridine)s (1)
- Amphiphilic polymers (1)
- Application (1)
- Aromatic organic compounds, (1)
- Aromatic pollutants (1)
- Artificial weathering (1)
- Aryl iodides (1)
- Asymmetric flow filed-flow fractionation (1)
- Asymmetrical flow field flow fractionation (AF4) (1)
- Attenuated total reflectance-Fourier transorm infrared spectroscopy (1)
- Biobased (1)
- Biodegradability (1)
- Biodegradable polyesters (1)
- Biopolymers (1)
- Biosourced isosorbide (1)
- Blockcopolymer (1)
- CRM (1)
- Caco-2 cells (1)
- Caesium (1)
- Capillary electrophoresis (1)
- Capillary electrophoresis (CE) (1)
- Carbon capture (1)
- Carbon fiberepoxy resin laminates (1)
- Carboxyl group (1)
- Catalytic ability (1)
- Cationic ring opening polymerization (1)
- Cationization (1)
- Chain scission (1)
- Chemical conversion of functional groups (1)
- Chemical reduction of functional groups (1)
- Classification (1)
- Click chemistry (1)
- Climate change (1)
- Conjugated oligomers (1)
- Controlled radical polymerization (1)
- Conversion (1)
- Copolyester (1)
- Copolymer composition (1)
- Copolymer sequence (1)
- Copolymeranalytik (1)
- Copolymerization (1)
- Copolymers (1)
- Cotton effect (1)
- Coupling (1)
- Coupling techniques (1)
- Cyclics (1)
- Cyclisation (1)
- Cycloaddition (1)
- Cycloparaphenylenes (1)
- DCTB (1)
- Degradation (1)
- Dendrimers (1)
- Dendrons (1)
- Depollution (1)
- Desorption (1)
- Dried droplet (1)
- Droplet (1)
- Dynamic light scattering (1)
- ESI-Massenspektrometrie (1)
- ESI-TOF MS (1)
- Electron paramagnetic resonance study (1)
- Electrospray (1)
- Electrospray ionization (ESI) (1)
- Epsilon-Caprolactone (1)
- Epsilon-caprolactone (e-CL) (1)
- Equilibration (1)
- Europium (1)
- Field flow fractionation (1)
- Foldamers (1)
- Fractionation of polymers (1)
- Fragmentierung (1)
- Friction (1)
- Ft-IR (1)
- Functionalized graphene nanoribbons (1)
- Fundamentals (1)
- Glycodendrimers (1)
- Glycolide (1)
- Gradient chromatography (1)
- Gradient elution (1)
- Gradient elution liquid chromatography (GELC) (1)
- Graphene monomers (1)
- Graphene nanoribbons (1)
- Graphene wires (1)
- Green chemistry (1)
- HPLC (1)
- Hafnium (1)
- Heavy metals (1)
- Hexabenzocoronene (1)
- Hierarchical cluster analysis (1)
- Hierarchical self-assembly (1)
- High performance liquid chromatography (1)
- Host–guest systems (1)
- Humidity (1)
- Hybrid nanoparticles (1)
- Hydrolytic degradation (1)
- Hyperbranched polyesters (1)
- Hyphenated techniques (1)
- Imaging MS (1)
- Imaging techniques (1)
- In situ EXAFS (1)
- In situ SAXS/WAXS (1)
- In vitro digestion (1)
- Inductively coupled plasma-mass spectrometry (1)
- Inlet ionization (1)
- Intrinsic viscosity (1)
- Ion mobility (1)
- Ionization mass spectrometry (1)
- Iron oxide nanoparticles (1)
- Irreversible polycondensation (1)
- Isophthalic acid (1)
- Jacobsen-Stockmayer theory (1)
- Kopplungsmethoden (1)
- L-lactide (1)
- LC-MS coupling (1)
- Lactides (1)
- Lacunary Keggin ion (1)
- Lanthanide ions (1)
- Laser-induced redox reactions (1)
- Layer topography (1)
- Lead ions (1)
- Light scattering (LS) (1)
- Linear (1)
- Liquid adsorption chromatography at critical conditions (1)
- Liquid chromatography at critical conditions (1)
- Liquid chromatography under critical conditions (LCCC) (1)
- Lubricant (1)
- MALDI Imaging MS (1)
- MALDI TOF Massenspektrometrie (1)
- MALDI TOF mass spectrometry (1)
- MALDI-TOF (1)
- MALDI-TOF MS/MS (1)
- MALDI-TOF Mass Spectrometry (1)
- MALDI-ToF MS (1)
- MOF (1)
- Mass Spectrometry (1)
- Mass spectrometry imaging (1)
- Materials Chemistry (1)
- Matrices (1)
- Matrix segregation (1)
- Matrix-assisted ionization ion mobility spectrometry mass spectrometry (1)
- Matrix-assisted laser desorption (1)
- Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) (1)
- Matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (1)
- Mechanism (1)
- Mechanism of polymerization (1)
- Mega-dalton (1)
- Metal ion complexation (1)
- Metal ion-intradendrimer complexes (1)
- Metal triflates (1)
- Metal-polymer interactions (1)
- Metal-polymer systems (1)
- Micro manufacturing (1)
- Microwave (1)
- Moisture (1)
- Molar mass determination (1)
- Molar mass distribution (1)
- Molecular masses (1)
- Molecular recognition (1)
- Morphology (1)
- Multicyclic polymers (1)
- Multiphysics simulations (1)
- Multivariate Statistics (1)
- Multivariate analyses (1)
- N-vinyl pyrrolidone (1)
- Nanolithography (1)
- Nanoparticle (1)
- Nanoparticles (1)
- Nanoparticles separation asymetrical flow field flow fractionation (1)
- Nanoparticles with same nominal diameter (1)
- Networks (1)
- Oligoazobenzene (1)
- Oligospiroketals (1)
- On-surface polymerization (1)
- Organic Chemistry (1)
- Oxygen low-pressure plasma treatment of polymers (1)
- PCA (1)
- PET (1)
- Partial least square discriminant analysis (PLS-DA) (1)
- Peel strength (1)
- Pentafluoropyridine (1)
- Phenolic acid (1)
- Phenolic compounds (1)
- Phenyleneethynylenes (1)
- Phosphonate esters (1)
- Photoligation (1)
- Photooxidation (1)
- Photoswitchable (1)
- Plasma (1)
- Plasma polymers with functional groups (1)
- Pollen grains (1)
- Poly(ether-phosphoramide)s sulfides (1)
- Poly(ethylene glycol) (1)
- Poly(ethylene terephthalate) (1)
- Poly(lactide) (1)
- Polyaddition (1)
- Polycaprolactone (1)
- Polycarbonate-co-dimethylsiloxane copolymer (1)
- Polycondensations (1)
- Polyelectrolytes (1)
- Polyethylene (1)
- Polyethylene oxide (1)
- Polyforamidine (1)
- Polykondensation (1)
- Polymer MALDI (1)
- Polymer blends (1)
- Polymer chromatography (1)
- Polymer film (1)
- Polymer mass spectrometry (1)
- Polymer reference materials (1)
- Polymerization mechanisms (1)
- Polymers and Plastics (1)
- Polyoxometalates (1)
- Polypropylene (1)
- Polysarcosine (1)
- Principal component analysis (PCA) (1)
- Quantification (1)
- ROMP (1)
- Raman (1)
- Renewable resources (1)
- Reversible addition/fragmentation chain transfer (RAFT) (1)
- Ring opening polymerization (ROP) (1)
- Ring-opening Polymerisation (1)
- Ring-opening polymerizations (1)
- Salicylate (1)
- Sample loss (1)
- Self-assembly (1)
- Semi-interpenetrating networks (1)
- Silica gel modification (1)
- Size exclusion chromatography (1)
- Size exclusion chromatography (SEC) (1)
- Size-exclusion chromatography (1)
- Sn catalysts (1)
- Soft ionization mass spectrometry (ESI, MALDI) (1)
- Software (1)
- Solvent-free (1)
- Sonoga (1)
- Sorption isotherm (1)
- Sorption mechanism (1)
- Spacers (1)
- Speciation (1)
- Spirocyclic (1)
- Stereocomplex (1)
- Succinic acid (1)
- Sulfobetaines (1)
- Supramolecular chemistry (1)
- Surface analysis (1)
- Surface coating (1)
- TPU (1)
- Tandem MS (1)
- Target plate material (1)
- Telechelic polyesters (1)
- Thermo-desorption (1)
- Thermochemistry (1)
- Thin polymer layers (1)
- Time of flight (1)
- Tin(II)octanoate (1)
- Toxicity (1)
- Toxicology (1)
- Triazenes (1)
- Two-dimensional off-line coupling (1)
- Two-dimensional-liquid chromatography (2D-LC) (1)
- UPLC (1)
- UV degradation (1)
- UV radiation (1)
- Ultraschallfalle (1)
- Universal calibration (1)
- Vacuum ionization (1)
- WMRIF (1)
- Water-soluble polymers (1)
- X-ray photoelectron spectroscopy (1)
- Zinc catalyst (1)
- a2 + b3 polycondensation (1)
- cyclization (1)
- dispersity (1)
- mass spectra (1)
- mass spectrometry (1)
- polycondensation (1)
- polyesters (1)
- polyionic liquids (1)
- r.f. pulsed plasma (1)
- reversible addition fragmentation chain transfer (RAFT) polymerization (1)
- ring-expansion polymerization (1)
- surface modification (1)
Organisationseinheit der BAM
- 6 Materialchemie (84)
- 6.3 Strukturanalytik (84)
- 1 Analytische Chemie; Referenzmaterialien (5)
- 1.2 Biophotonik (2)
- 1.7 Organische Spuren- und Lebensmittelanalytik (2)
- 6.6 Physik und chemische Analytik der Polymere (2)
- 7 Bauwerkssicherheit (2)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (2)
- 1.0 Abteilungsleitung und andere (1)
- 1.3 Instrumentelle Analytik (1)
- 1.4 Prozessanalytik (1)
- 4 Material und Umwelt (1)
- 4.3 Schadstofftransfer und Umwelttechnologien (1)
- 5 Werkstofftechnik (1)
- 5.6 Glas (1)
- 6.0 Abteilungsleitung und andere (1)
- 8 Zerstörungsfreie Prüfung (1)
- 8.5 Röntgenbildgebung (1)
- 9 Komponentensicherheit (1)
- 9.5 Tribologie und Verschleißschutz (1)
Eingeladener Vortrag
- nein (12)
The adhesion of poly(methyl methacrylate) (PMMA) and polystyrene (PS) films, whose surface has been previously structured by dynamic plowing lithography (DPL), has been measured by means of forcedisplacement curves. The different adhesion of modified and unmodified PS leads to the assumption that polymer chains are broken during DPL. After measuring the energy dissipated by the tip during DPL, in order to check that the transferred energy is sufficient to break covalent bonds, the polymer chain scission caused by the lithographic process has been definitely confirmed by size exclusion chromatography measurements of the lithographed films.
Phase Behaviour of Copolymers Containing Cholesterol and 4,4' Methoxybiphenyl as Mesogenic Group
(1996)
The influence of electric field strength and emitter temperature on dehydrogenation and CC cleavage in field desorption (FD) mass spectrometry of polyethylene (PE) oligomers of average molecular weights ranging from 500 to 2000 is examined. Low mass oligomers yield molecular weight (MW) distributions that are basically in accordance with results from gel-permeation chromatography. For these materials, dehydrogenation can be greatly reduced by reduction of the emitter potential. Furthermore, the influence of emitter potential on MW distributions indicates the occurrence of field-induced CC cleavages. Reliable MW distributions are more difficult to obtain from higher mass oligomers by FD-MS because of the need for higher field strength and higher emitter temperatures to effect their desorption/ionization. Experiments reveal that the application of FD-MS to PE oligomers is limited not only by field-induced but also by thermally-induced fragmentations. Even then, FD mass spectra contain valuable information on mass range and homogeneity of PE samples up to about m/z 3600.
Alkyl polyglycosides today represent the most important sugar surfactant. Nonionic sugar surfactants produced via different synthetic routes are mixtures of alkyl homologues, oligomers, anomers and isomers. Alkyl homologues and oligomers of alkyl mono- and diglucosides were separated by reversed-phase high-performance liquid chromatography (HPLC) with methanolwater as the mobile phase using a gradient elution. The gradient was optimized in respect to a simultaneous separation of alkyl glycosides according to their alkyl chain length and alkyl polyoxyethylene glucosides with regard to their length of the polyoxyethylene spacer. The separation of alkyl glycosides into ?- and ?-anomers was carried out by normal-phase HPLC with isooctaneethyl acetate (60:40, v/v)2-propanol in the gradient mode. Light scattering detection was used. Matrix-assisted laser desorption ionization time-of-flight mass spectra of alkyl glucosides and dodecyl glucosides with oxyethylene spacer groups are presented.
A family of rigid rod like 2,5-dodecanoxy-phenyleneethynylene oligomers having 3, 5, 7, and 9 repeating units was selectively synthesized by a bi-directional iterative divergent-convergent approach. Starting from a central 1,4-bis(dodecanoxy)-2,5-diiodobenzene monomer, only two repetitive reactions were involved with each cycle of oligomerization: a Pd/Cu cross-coupling with the bifunctional monomer 1-(3,3-diethyltriazene)-2,5-bis(dodecanoxy)-4-(ethynyl)benzene, generating oligomers with terminal triazene groups, followed by a further nucleophilic substitution with iodine.
Influence of Chirality on Phase Behaviour of Copolymers Containing Cholesterol as Mesogenic Group
(1996)
The chemical and morphological stabilities of polymer segments in the near-surface layer were investigated by spectroscopic methods such as X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. Model studies were undertaken with LangmuirBlodgett films, self-assembled monolayers and oligomer films. For thin polymer layers (30 to 500 nm), the changes in molecular-weight distributions of some polymers were investigated systematically by size exclusion chromatography, matrix-assisted laser desorption/ionizationtime-of-flight mass spectrometry and thermal-field flow fractionation for oxygen- and helium-plasma exposures. The polymer surfaces were found to be relatively stable at exposure to an oxygen low-pressure plasma up to ca. 2 s. This is important information to get maximum adhesion to metals in composites. In correlation to their redox potentials, potassium, aluminium and chromium react with oxygen functional groups at the polymer/metal interface. In a dedicated study, chromium was found to attack aromatic rings and form different reaction products.
Polymer surfaces can be finished with functional groups upon exposure to a plasma. Species of the plasma gas are attached at surface carbon atoms, forming functional groups of different composition. To produce a modified polymer surface with a high density and homogeneity of hydroxyl groups only, the oxygen-plasma-formed oxygen functional groups were chemically reduced by diborane and LiAlH4 with yields of 10 to 11 OH groups per 100 carbon atoms in the 3 to 5 nm near-surface layer as detected by X-ray photoelectron spectroscopy (XPS). The identification of hydroxyl groups was performed by means of attenuated total reflectanceFourier transform infrared spectroscopy and XPS.
The influence of different types of low and atmospheric pressure plasma on poly(ethylene terephthalate) (PET) has been studied in terms of changes in molar mass and molar mass distribution. Apart from a variation of plasma gases (oxygen, helium) different types of plasma (microwave, radio frequency, corona discharge) were used for the plasma surface modification. The changes in molar mass and types of functional end groups of lower molar mass products were investigated by means of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOFMS), whereas the high-molar mass fraction was analyzed by means of size-exclusion chromatography (SEC). The formation of crosslinked products during exposure to a helium plasma, which emits preponderately energy-rich and intense ultraviolet radiation, was proved by means of thermal field-flow fractionation (ThFFF). This method combined with a multiangle laser light scattering (MALLS) detector allows detection of weakly crosslinked polymers and microgels. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1639-1648, 1998
Modelling plasma-induced reactions on polymer surfaces using aliphatic self-assembling and LB layers
(1998)
The detection limits of matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) by semi-online coupling with chromatography were investigated using various mixtures of polyethylene oxides (PEOs) with different end groups. In contrast to the common dried-droplet sample preparation technique, which results in an inhomogeneous sample-to-matrix ratio within the MALDI spot, the used coupling technique offers a very high reproducibility combined with surpassing sensitivity of a few femtograms over a broad range of sample-to-matrix ratios. These results are in correlation with the results of the recently established solvent-free MALDI-TOFMS method utilising the grinding approach and are also of assistance towards the more theoretical aspect of MALDI that suggests that there is no necessity for an analyte incorporation into a matrix crystal for excellent matrix-assistance.
Polybutadienes (PB) and polyisoprenes (PI) with various molecular weights and polydispersities were epoxidized applying two different synthetic routes. The degree of epoxidation was determined by means of matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). It has been found that the degree of functionalization of polybutadiene is generally lower than that for polyisoprenes. Additionally, PB shows lower degrees of epoxidation at higher masses, whereas the level of functionalization of PI was unaffected by the molar mass. Coupling of gel permeation chromatography (GPC) with MALDI-TOF mass spectrometry was successfully used for the investigation of epoxidized polymers with higher masses. Using mass spectra of single fractions, the degree of epoxidation could be determined and applied for a calibration of GPC.
A solvent-free homogenization/transfer matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) method is described for the preparation and precise transfer of up to 100 samples simultaneously on a single MALDI plate. This method is demonstrated using a poly(ethylene oxide) (PEO) mixture consisting of different molecular weights (500-6000) and end groups (PEO, dimethoxy-PEO, monomethoxy monomethacrylate-PEO, and dimethacrylate-PEO) that was fractionated using liquid adsorption chromatography at critical conditions. Off-line fractionation is performed prior to the on-target homogenization/transfer solvent-free sample preparation and MALDI mass analysis. The miniaturization of the solvent-free MALDI approach allowed analysis of less than 2 g per PEO component per fraction corresponding to ~200 pmol for PEO 6000. The amounts of polymer sample used for LC separation and the quality of the MS results are equivalent to the "dry spray" method; however, three times more fractions were collected and analyzed with the newly developed hyphenated approach. The off-line method eliminates optimization of, for example, spray conditions or spreading of organic solvents on the MALDI plate that occurs with droplet deposition methods. The widespread applications of MALDI make this solvent-free, multisample method particularly important as it expands the capabilities for obtaining mass measurements with great efficiencies in areas with increased sample numbers. In addition, the solvent-free method is well suited for automated MALDI analysis as it virtually eliminates the "dead-spot" phenomenon.
Two-dimensional polymer characterization is used for a simultaneous analysis of molar masses and chemical heterogeneities (e.g., end groups, copolymer composition, etc.). This principle is based on coupling of two different chromatographic modes. Liquid adsorption chromatography at critical conditions (LACCC) is applied for a separation according to the chemical heterogeneity, whereas in the second-dimension fractions are analyzed with regard to their molar mass distribution by means of size exclusion chromatography (SEC). Because appropriate standards for a calibration of the SEC are seldom available, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) was used to substitute the SEC. The LACCC-MALDI MS coupling enables acquiring additional structural information on copolymer composition, which can considerably enhance the performance of this coupled method.
The results of copolymer characterization by coupling of chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) techniques and subsequent calculation of copolymer composition using a novel software tool MassChrom2D are presented. For high-resolution mass analysis copolymer samples were fractionated by means of liquid adsorption chromatography (LAC). These fractions were investigated off-line by MALDI-TOF MS. Various mono-n-butyl ethers of polyethylene oxide-polypropylene oxide copolymers (PEO-co-PPO) were investigated. As well as the copolymer composition presented in two-dimensional plots, the applied approach can give additional hints on specific structure-dependent separation conditions in chromatography.
New amphiphilic block copolymers consisting of N-vinyl pyrrolidone and vinyl acetate were synthesized via controlled radical polymerization using a reversible addition/fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) system. The synthesis was carried out in 1,4-dioxane as process solvent. In order to get conclusions on the mechanism of the polymerization the molecular structure of formed copolymers was analysed by means of different analytical techniques. 13C NMR spectroscopy was used for the determination of the monomer ratios. End groups were analysed by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This technique was also used to determine possible fragmentations of the RAFT end groups. By means of a combination of size exclusion chromatography, 13C NMR and static light scattering molar mass distributions and absolute molar masses could be analysed. The results clearly show a non-ideal RAFT mechanism.
Two decades after the introduction of matrix assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI), soft ionization mass spectrometry represents a powerful toolset for the structural investigation of synthetic polymers. The present review highlights the current state-of-the-art, covering the latest developments of novel techniques, enabling instrumentation as well as the important applications of soft ionization MS from the beginning of 2008. Special attention is paid to the role that soft ionization MS has played in the mechanistic investigation of radical polymerization processes since 2005.
The dispersed iron oxide nanoparticles of ferrofluids in aqueous solution are difficult to characterize due to their protective polymer coatings. We report on the bimodal size distribution of superparamagnetic iron oxide nanoparticles found in the MRI contrast agent Resovist, which is a representative example of commercial nanoparticle-based pharmaceutical formulations. The radii of the majority of the nanoparticles (>99%) range from 4 to 13 nm (less than 1% of the particles display radii up to 21 nm). The maxima of the size distributions are at 5.0 and 9.9 nm. The analysis was performed with in situ characterization of Resovist via online coupling of asymmetrical flow field-flow fractionation (A4F) with small-angle X-ray scattering (SAXS) using a standard copper X-ray tube as a radiation source. The outlet of the A4F was directly coupled to a flow capillary on the SAXS instrument. SAXS curves of nanoparticle fractions were recorded at 1-min time intervals. We recommend using the A4F-SAXS coupling as a routine method for analysis of dispersed nanoparticles with sizes in the range of 1-100 nm. It allows a fast and quantitative comparison of different batches without the need for sample preparation.
We report on a hyphenated polymer analysis method consisting of asymmetrical flow field-flow fractionation (A4F) coupled online with small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS). A mixture of six poly(styrene sulfonate)s with molar masses in the range of 6.5 × 103 to 1.0 × 106 g mol-1 was used as a model system for polyelectrolytes in aqueous solutions with a broad molar mass distribution. A complete polymer separation and analysis was performed in 60 min. Detailed information for all polymer fractions are available on i) the radii of gyration, which were determined from the SAXS data interpretation in terms of the Debye model (Gaussian chains), and ii) the diffusion coefficients (from DLS). We recommend using the A4F-SAXS-DLS coupling as a possible new reference method for the detailed analysis of complex polymer mixtures. Advantages of the use of SAXS are seen in comparison to static light scattering for polymers with radii of gyration smaller then 15 nm, for which only SAXS produces precise analytical results on the size of the polymers in solution.
Chemical heterogeneities and molecular weight distributions of poly(ethylene oxide) (PEO)-co-polymethylene (PM) model oligomers, which are relevant to the synthesis of commonly used tensides, were investigated. For analytical characterization, the well-known principle of liquid adsorption chromatography at 'critical conditions' (LACCC) was modified. Near the critical conditions of adsorption of the PEO unit, e.g., at slight adsorption conditions of PM, the copolymers could be separated according to their PM chain length. The eluates were separated and single fractions of each peak were continuously transferred onto the MALDI target by means of a commercially available device. Simultaneously, the MALDI matrix solution was continuously added with a second pump. This procedure offers the possibility of the formation of homogeneous matrix-polymer textures. By MALDI-MS a complete characterization of the chemical composition (PEO and PM chain length) of each peak could be achieved. The obtained MALDI mass spectra of the eluates at different retention times could be used for the molecular weight calibration of the LAC system. In this way, an additional application of SEC, as in conventional 2D-chromatography, was avoided by using the MALDI method as quasi chromatographic separation
Liquid chromatography (LC) at critical conditions of adsorption was used to separate various poly(ethylene oxides), poly(propylene oxides) and their copolymers. For the first time, the determination of the critical conditions by means of Ultra Performance Liquid Chromatography (UPLC) coupled to Electrospray Ionization Time-of-flight Mass Spectrometry (ESI-TOF MS) is reported. In contrast to established, mostly laborious routines to find suitable chromatographic separation conditions, this coupling enables a very fast adjustment of parameters. Similar to LC Matrix-assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (LC/MALDI MS) coupling, a two-dimensional analysis of homo- and copolymers regarding its functionality type and molecular weight distribution, as well as copolymer composition, can be performed simultaneously. Furthermore, there is no need for using polymer standards for the determination of critical conditions or Size Exclusion Chromatography calibration.
The localization of polymeric composition in samples prepared for matrix-assisted laser desorption/ionization (MALDI) analysis has been investigated by imaging mass spectrometry. Various matrices and solvents were used for sample spot preparation of a polybutyleneglycol (PBG 1000). It was shown that in visibly homogeneous spots, prepared using the dried droplet method, separation between matrix and polymer takes place. Moreover, using -cyano-4-hydroxycinnamic acid (CCA) as matrix and methanol as solvent molecular mass separation of the polymer homologues in the spots was detectable. In contrast to manually spotted samples, dry spray deposition results in homogeneous layers showing no separation effects.