TY - JOUR A1 - Lauer, Franziska A1 - Diehn, Sabrina A1 - Seifert, Stephan A1 - Kneipp, Janina A1 - Sauerland, V. A1 - Barahona, C. A1 - Weidner, Steffen T1 - Multivariate analysis of MALDI imaging mass spectrometry data of mixtures of single pollen grains N2 - Mixtures of pollen grains of three different species (Corylus avellana, Alnus cordata, and Pinus sylvestris) were investigated by matrixassisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF imaging MS). The amount of pollen grains was reduced stepwise from > 10 to single pollen grains. For sample pretreatment, we modified a previously applied approach, where any additional extraction steps were omitted. Our results show that characteristic pollen MALDI mass spectra can be obtained from a single pollen grain, which is the prerequisite for a reliable pollen classification in practical applications. MALDI imaging of laterally resolved pollen grains provides additional information by reducing the complexity of the MS spectra of mixtures, where frequently peak discrimination is observed. Combined with multivariate statistical analyses, such as principal component analysis (PCA), our approach offers the chance for a fast and reliable identification of individual pollen grains by mass spectrometry. KW - MALDI Imaging MS KW - Pollen grains KW - Multivariate Statistics KW - Hierarchical cluster analysis KW - Principal component analysis PY - 2018 DO - https://doi.org/10.1007/s13361-018-2036-5 SN - 1044-0305 SN - 1879-1123 VL - 29 IS - 11 SP - 2237 EP - 2247 PB - Springer AN - OPUS4-45607 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scholz, Philipp A1 - Wachtendorf, Volker A1 - Panne, Ulrich A1 - Weidner, Steffen ED - Scholz, Philipp T1 - Degradation of MDI-based polyether and polyester-polyurethanes in various environments - Effects on molecular mass and crosslinking N2 - Size-exclusion chromatography (SEC) was used to monitor changes of the molecular masses of thermoplastic polyether – and polyester urethane (TPU) exposed to thermal, hydrolytic, and photo-oxidative (UV) Degradation conditions for several days. The thermal treatment was performed at elevated temperatures (100–200 °C) under oxidative (air) as well as non-oxidative (nitrogen) conditions to evaluate the specific influence of oxygen on the degradation. At higher temperatures (≥175 °C) a fast decrease of the molecular masses of both PU accompanied by a high degree of crosslinking was found. At lower temperatures (≤150 °C) the polymers remained widely unaffected by thermal degradation within the investigated degradation interval of up to two weeks. Surprisingly, the influence of oxygen (air) was found to be less distinct. In contrast to that, UV treatment at 25 °C at less than 10% rel. humidity (RH) resulted in a fast crosslinking, whereas the molecular masses of both PU decreased slower than for thermal treatments. The depth of penetration of the UV radiation was estimated using 3D printed PU samples with different thicknesses. Hydrolysis based degradation effects were less significant. Only slight molecular mass changes were detected at temperatures ≤80 °C within a time span of 14 days, while no crosslinking could be measured. Considering the degradation results at the investigated exposure parameters, it could be shown that esterbased PU in general exhibits a significant higher stability compared to ether-based materials. KW - Polyurethane KW - Thermal degradation KW - UV degradation KW - Molecular masses KW - Crosslinking PY - 2019 UR - https://www.sciencedirect.com/science/article/pii/S0142941819302363 DO - https://doi.org/10.1016/j.polymertesting.2019.04.028 SN - 0142-9418 VL - 77 SP - 105881, 1 EP - 12 PB - Elsevier CY - Amsterdam AN - OPUS4-48619 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Weidner, Steffen T1 - High Tg copolyesters of lactide, isosorbide and isophthalic acid N2 - Using SnCl2, ZnCl2, Zn-lactate or Zr-acetylacetonate as catalysts ʟ-lactide was oligomerized in bulk with isosorbide as initiator. The ratio isosorbide/lactide was varied from 8/2 to 2/8. The resulting oligomers were in situ polycondensed with isophthaloyl chloride in various aromatic solvents. In chlorobenzene homogeneous reaction mixtures were obtained, whereas molten copolyesters precipitated from toluene and xylene. The obtained average molecular weights indicated high polydispersities. According to MALDI-TOF MS the low molar mass reaction products (<4 kDa) almost exclusively consisted of cyclics with a composition depending on the feed ratio. The glass-transition temperatures (Tg) varied between the values of poly(ʟ-lactide (64 °C) and poly(isosorbide isophthalate) (180 °C). Four polyesters prepared from 5-tert-butyl isophthalic acid displayed higher Tg values. Differential thermoanalysis evidenced that the thermostability decreases with higher fractions of lactide, but processing from the melt seems to be feasible up to temperatures of 260 °C without risking degradation. KW - Lactide KW - Isosorbide KW - Ring-opening polymerization KW - Polycondensation KW - Cyclization PY - 2013 DO - https://doi.org/10.1016/j.eurpolymj.2013.05.007 SN - 0014-3057 SN - 1873-1945 VL - 49 IS - 8 SP - 2293 EP - 2302 PB - Elsevier CY - Oxford AN - OPUS4-29014 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Weidner, Steffen T1 - Copolyesters of lactide, isosorbide, and terephthalic acid-biobased, biodegradable, high-Tg engineering plastics N2 - Various copolyesters of lactide, isosorbide, and terephthalic acid are prepared by a two-step process performed in a 'one-pot' procedure, beginning with an isosorbide-initiated oligomerization of L-lactide followed by polycondensation with terephthaloyl chloride using SnCl2 as a catalyst for both steps. The SEC data show the formation of random copolyesters with high polydispersities as a consequence of the relatively high fraction of cyclics proved by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The glass-transition temperatures (89–180 °C) obey an almost linear trend with the molar composition. The thermostability decreases with increasing lactide content. The successful incorporation of phenyl phosphate results in copolyesters of lower inflammability. KW - Biodegradability KW - Cyclization KW - Isosorbide KW - Polycondensation KW - Ring-opening polymerization PY - 2013 DO - https://doi.org/10.1002/macp.201200612 SN - 1022-1352 SN - 1521-3935 VL - 214 IS - 6 SP - 726 EP - 733 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-28171 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Holländer, A. A1 - Kühn, Gerhard T1 - Matrix-assisted Laser Desorption/Ionization Mass Spectrometry of C36- Alkane degradated by Vacuum Ultraviolet Radiation PY - 1997 SN - 0951-4198 SN - 1097-0231 VL - 11 SP - 447 EP - 450 PB - Wiley CY - Chichester AN - OPUS4-11095 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Falkenhagen, Jana A1 - Friedrich, Jörg Florian A1 - Schulz, Günter A1 - Krüger, Ralph-Peter A1 - Much, Helmut A1 - Weidner, Steffen T1 - Liquid Adsorption Chromatography near Critical Conditions of Adsorption coupled with Matrix-assisted Laser Desorption/Ionization Mass Spectrometry N2 - 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 KW - Liquid adsorption chromatography KW - Matrix-assisted laser desorption KW - Ionization mass spectrometry KW - Coupling methods KW - MALDI PY - 2000 DO - https://doi.org/10.1080/10236660008034644 SN - 1023-666X SN - 1563-5341 VL - 5 SP - 549 EP - 562 PB - Gordon and Breach Publ. CY - Amsterdam AN - OPUS4-2168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Kühn, Gerhard A1 - Werthmann, Barbara A1 - Schröder, Hartmut A1 - Just, Ulrich A1 - Borowski, Renate A1 - Decker, Renate A1 - Schwarz, Bärbel A1 - Schmücking, I. A1 - Seifert, Ingetraut T1 - A new approach of characterizing the hydrolytic degradation of poly(ethylene terephthalate) by MALDI-MS N2 - The hydrolytic degradation of technical poly(ethylene terephthalate) (PET) was investigated by means of different methods such as size-exclusion chromatography (SEC), viscometry, light-scattering, thin-layer chromatography, end-group titration, and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The long-term degradation was simulated by exposing PET filament yarns to aqueous neutral conditions at 90°C for up to 18 weeks. By means of MALDI-MS and thin-layer chromatography, the formation of different oligomers was obtained during polymer degradation. As expected, an ester scission process was found generating acid terminated oligomers (H-[GT]m-OH) and T-[GT]m-OH and ethylene glycol terminated oligomers (H-[GT]m-G), where G is an ethylene glycol unit and T is a terephthalic acid unit. Additionally, the scission of the ester bonds during the chemical treatment led to a strong decrease in the number of cyclic oligomers ([GT]m). The occurrence of di-acid terminated species demonstrated a high degree of degradation. PY - 1997 DO - https://doi.org/10.1002/(SICI)1099-0518(199708)35:11<2183::AID-POLA9>3.0.CO;2-Z SN - 0360-6376 SN - 0887-624X VL - 35 IS - 11 SP - 2183 EP - 2192 PB - Wiley CY - Hoboken, NJ AN - OPUS4-11357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Kühn, Gerhard A1 - Friedrich, Jörg Florian A1 - Unger, Wolfgang A1 - Lippitz, Andreas T1 - Plasmaoxidative Degradation of Polymers Studied by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry PY - 1996 SN - 0951-4198 SN - 1097-0231 VL - 10 SP - 727 EP - 732 PB - Wiley CY - Chichester AN - OPUS4-7004 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Trimpin, s. T1 - Mass Spectrometry of Synthetic Polymers KW - Polymere KW - Massenspektrometrie KW - MALDI PY - 2010 DO - https://doi.org/10.1021/ac101080n SN - 0003-2700 SN - 1520-6882 VL - 82 IS - 12 SP - 4811 EP - 4829 PB - American Chemical Society CY - Washington, DC AN - OPUS4-21623 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Soulis, S. A1 - Triantou, D. A1 - Weidner, Steffen A1 - Falkenhagen, Jana A1 - Simitzis, J. T1 - Structural analysis of biodegradable low-molecular mass copolyesters based on glycolic acid, adipic acid and 1,4 butanediol and correlation with their hydrolytic degradation N2 - Copolyesters of glycolic acid combined with adipic acid and 1,4 butanediol were synthesized, their in vitro hydrolytic degradation was studied and correlated with their structure. The hydrolytic degradation of the copolyesters was directly related with the degree of crystallinity and the diameter of the crystallites. It was found that glycolate units disturb the ordering of the butylene adipate units, which results in a decrease of the crystallinity. By comparing the hydrolysis parameters of synthesized copolyesters with those of similar aliphatic copolyesters a hydrolysis mechanism was proposed. According to this mechanism, the degradation takes place not only by the loss of end units, but also through the removal of larger segments. MALDI-TOF MS data showed that the possibility of a copolyester macromolecule forming cyclic structures correlates with the arrangement of ester groups in the macromolecules and the structure of the linear segments. KW - Biodegradable KW - Biopolymers KW - Hydrolytic degradation KW - Ft-IR KW - Matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry KW - MALDI-TOF-MS PY - 2012 DO - https://doi.org/10.1016/j.polymdegradstab.2012.09.002 SN - 0141-3910 SN - 1873-2321 VL - 97 IS - 11 SP - 2091 EP - 2103 PB - Applied Science Publ. CY - London AN - OPUS4-26723 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -