TY - JOUR A1 - Sötebier, Carina A. A1 - Weidner, Steffen A1 - Jakubowski, Norbert A1 - Panne, Ulrich A1 - Bettmer, J. T1 - Separation and quantification of silver nanoparticles and silver ions using reversed phase high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry in combination with isotope dilution analysis N2 - A reversed phase high performance liquid chromatography coupled to an inductively coupled Plasma mass spectrometer (HPLC–ICP-MS) approach in combination with isotope dilution analysis (IDA) for the separation and parallel quantification of nanostructured and ionic silver (Ag) is presented. The main Focus of this work was the determination of the ionic Ag concentration. For a sufficient stabilization of the Ions without dissolving the nanoparticles (NPs), the eluent had to be initially optimized. The determined Ag ion concentration was in a good agreement with results obtained using ultrafiltration. Further, the mechanism of the NP separation in the HPLC column was investigated. Typical size exclusion effects were found by comparing results from columns with different pore sizes. Since the recovery rates decreased with increasing Ag NP size and large Ag NPs did not elute from the column, additional interactions of the particles with the stationary phase were assumed. Our results reveal that the presented method is not only applicable to Ag NPs, but also to gold and polystyrene NPs. Finally, IDA-HPLC-ICP-MS experiments in single particle mode were performed to determine the particle cut-off size. The comparison with conventional spICP-MS experiments resulted in a similar diameter and particle size distribution. KW - ICP-MS KW - Silver nanoparticles KW - Speciation KW - High performance liquid chromatography KW - Isotope dilution analysis PY - 2016 DO - https://doi.org/10.1016/j.chroma.2016.09.028 SN - 0021-9673 VL - 1468 SP - 102 EP - 108 AN - OPUS4-37652 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, Hans A1 - Weidner, Steffen T1 - High molar mass cyclic poly(L-lactide) via ring-expansion polymerizationwith cyclic dibutyltin bisphenoxides N2 - Two new catalysts (SnNa and SnBi) were prepared from dibutyltin oxide and 2,2′-dihydroxybiphenyl or2,2′dihydroxy(1,1′-binaphtyl). These catalysts enabled rapid polymerizations of L-lactide at 160 or 180 °C in bulk, whereby almost exclusively cyclic polylactides were formed. These polymerizations were free of racemization and yielded pol(L-lactide)s having weight average molecular weights (Mw's) up to 140 000 g mol−1. The Mw's varied little with the Lac/Cat ratio as expected for a ring expansion polymerization (REP). Polymerizations performed in bulk at 140, 120 and 102 °C yielded cyclic polylactides with lower molecular weights. At 102 °C a strong predominance of even-numbered cycles was found with SnNa as catalyst. SnNa can also catalyze alcohol-initiated ROPs yielding linear poly(L-lactide) free of cyclics. KW - MALDI-TOF MS KW - Polylactide KW - Ring-opening Polymerization KW - Cyclization KW - Catalysts PY - 2018 DO - https://doi.org/10.1016/j.eurpolymj.2018.05.036 SN - 0014-3057 SN - 1873-1945 VL - 105 SP - 158 EP - 166 PB - Elsevier Ltd. AN - OPUS4-45439 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Billing, Mark A1 - Gräfe, Christine A1 - Saal, Adrian A1 - Biehl, Philip A1 - Clement, Joachim A1 - Dutz, silvio A1 - Weidner, Steffen A1 - Schacher, Felix T1 - Zwitterionic Iron Oxide (γ-Fe2O3) Nanoparticles Based on P(2VP-grad-AA) Copolymers N2 - This study presents the synthesis and characterization of zwitterionic core–shell hybrid nanoparticles consisting of a core of iron oxide multicore nanoparticles (MCNPs, γ-Fe2O3) and a shell of sultonated poly(2-vinylpyridine-grad-acrylic acid) copolymers. The gradient copolymers are prepared by reversible addition fragmentation chain transfer polymerization of 2-vinylpyridine (2VP), followed by the addition of tert-butyl acrylate and subsequent hydrolysis. Grafting of P(2VP-grad-AA) onto MCNP results in P(2VP-grad-AA)@MCNP, followed by quaternization using 1,3-propanesultone-leading to P(2VPS-grad-AA)@MCNP with a zwitterionic shell. The resulting particles are characterized by transmission electron microscopy, dynamic light scattering, and thermogravimetric analysis measurements, showing particle diameters of ≈70–90 nm and an overall content of the copolymer shell of ≈10%. Turbidity measurements indicate increased stability toward secondary aggregation after coating if compared to the pristine MCNP and additional cytotoxicity tests do not reveal any significant influence on cell viability. KW - Blockcopolymer KW - Controlled radical polymerization KW - Hybrid nanoparticles KW - Iron oxide nanoparticles KW - Sulfobetaines PY - 2017 DO - https://doi.org/10.1002/marc.201600637 SN - 1022-1336 SN - 1521-3927 VL - 38 IS - 4 SP - 1600637-1 EP - 1600637-8 PB - Wiley-VCH AN - OPUS4-39339 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mechichi, R. A1 - Chabbah, T. A1 - Chatti, S. A1 - Jlalia, I. A1 - Sanglar, Corinne A1 - Casablanca, H. A1 - Vulliet, E. A1 - Marestin, C. A1 - Mercier, R. A1 - Weidner, Steffen A1 - Errachid, A. A1 - Hammani, M. A1 - Jaffrezic-Renault, N. A1 - Abderrazak, H. T1 - Semi‑interpenetrating Network‑Coated Silica Gel Based on Green Resources for the Efcient Adsorption of Aromatic Pollutants from Waters N2 - In the framework of the development of green analytical chemistry, a silica gel (SG) coated with a semi-penetrating network based on the partially biosourced poly(ethersulfone) is studied for a greener extraction process of aromatic organic pollutants. An optimized composition of the semi-penetrating network (80% of the linear polymer (LP): isosorbide-based poly(ethersulfone) and 20% cross-linking agent (XP) type bismaleimide) leads to a total adsorption of the selected aromatic pollutants, whatever their hydrophilicity. Adsorption characteristic, kinetics and isotherms of the SG-semi-INP LP80/XP20 for p-hydroxybenzoic acid and for toluic acid were studied. Langmuir model led to a better ftting of the adsorption isotherms; the adsorption of toluic acid is easier than that of p-hydroxybenzoic acid. 1/n values of benzoic acid was lower for SGsemi-INP LP80/XP20 compared to biochar and to cross-linked methacrylate resin, showing a higher adsorption efciency. KW - Isosorbide KW - Semi-interpenetrating networks KW - Silica gel modification KW - Aromatic pollutants KW - Adsorption PY - 2022 DO - https://doi.org/10.1007/s42250-022-00463 SN - 2522-5758 SP - 1 EP - 18 PB - Springer AN - OPUS4-55720 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, Hans R. A1 - Weidner, Steffen T1 - Ring-expansion polymerization of meso-lactide catalyzed by dibutyltin derivatives N2 - Meso-Lactide was polymerized in bulk at 60, 80, and 100 °C by means of three different types of catalysts: dibutyltinsulfides (2,2-dibutyl-2-stanna-1,3-dithiolane and 2,20-dibutyl-2-stanna-1,3-dithiane), dibutyltin derivatives of substituted cate-chols (BuCa, CyCa, and BzCa), and dibutyltin derivatives of2,2 dihydroxybiphenyl (SnBi) and 2,2-dihydroxy-1,10-binaphthyl(SnNa. Only the latter two catalysts were active at 60 °C. The architecture of the resulting polylactides depends very much on the structure of the catalyst and on the temperature. At the lowest temperature (60 °C), SnBi and SnNa mainly yielded even-numbered linear chains, but SnNa also yielded even-numbered cycles at 100 °C and short reaction times. In contrast,BuCa, CyCa, and BzCa mainly yielded odd-numbered cycles, although the same catalysts yielded even-numbered linear chains when benzylalcohol was added. KW - MALDI-TOF MS KW - Cyclisation KW - Catalysts KW - Polyester KW - Polymerization PY - 2018 DO - https://doi.org/10.1002/pola.28948 SN - 1099-0518 SN - 0022-3832 VL - 56 IS - 7 SP - 749 EP - 759 PB - Wiley Periodicals Inc. AN - OPUS4-44278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Kricheldorf, H. T1 - Transesterification in alcohol-initiated ROPs of l- and meso-lactide catalyzed by Sn(II) and Sn(IV) compounds at low temperatures N2 - The purpose of this study is to shed more light on the transesterification processes in alcohol-initiated and tin(II) 2-ethylhexanoate (SnOct2)-catalyzed polymerizations of lactides at low or moderate temperatures. Ethanol-initiated polymerizations are conducted in concentrated solutions at 80 °C and a strong dependence of even/odd equilibration on the alcohol/Sn ratio. Around or above 120 °C cyclization of poly(l-lactide) via “backbiting” occurs as a third mechanism. However, poly(m-lactide) shows a higher cyclization tendency and yields cyclics even at 100 °C. Combinations of ethanol and certain cyclic dibutyltin(IV) catalysts also yield cyclic oligomers of l-lactide at 80 °C. Reaction conditions allowing for a total suppression of all transesterification reactions are not found, but even-numbered poly(m-lactide)s with a purity >95% are obtained at 70 or 60 °C. KW - Cyclization KW - MALDI-TOF MS KW - Polyester KW - Polylactide KW - Transesterification PY - 2018 DO - https://doi.org/10.1002/macp.201800445 SN - 1022-1352 SN - 1521-3935 VL - 219 IS - 24 SP - 1800445, 1 EP - 10 PB - Wiley-VCH CY - Weinheim AN - OPUS4-46705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen T1 - Cyclic poly(L-lactide)s via simultaneous ROP and polycondensation (ROPPOC) catalyzed by dibutyltin phenoxides N2 - Starting from dibutyltin oxide, four catalysts were synthesized, namely the dibutyltin bisphenoxides of Phenol (SnPh), 4-chlorophenol (SnCP), 4-hydroxybenzonitrile (SnCN) and pentafluorophenol (SnOPF). With the first three catalysts polymerizations of L-lactide at 160 °C in bulk yielded large fraction of linear chains having phenylester end groups at short reaction times. At longer times the fraction of cycles considerably increased at the expense of the linear chains, when SnCN was used as catalyst. With SnOPF only cyclic polylactides were obtained at low Lac/Cat ratios (< 400) with weight average molecular weights (Mw) up to 90 000 Da, whereas for high Lac/Cat ratios mixtures of cyclic and linear chains were found. Polymerizations in solution enabled variation of the molecular weight. Polymerizations of meso-lactide at temperatures down to 60 °C mainly yielded even-numbered linear chains supporting the postulated ROPPOC mechanism. KW - Cyclization KW - MALDI-TOF MS KW - Polycondensation KW - Ring-opening Polymerization KW - Polylactide PY - 2018 DO - https://doi.org/10.1016/j.eurpolymj.2018.10.005 SN - 0014-3057 IS - 109 SP - 360 EP - 366 PB - Elsevier AN - OPUS4-46263 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weidner, Steffen T1 - MALDI-MS zur Aufklärung des Mechanismus der homogen katalysierten Polymerisation flüssigkristalliner Seitengruppenmethacrylate T2 - III. BAM-Kolloquium zu "Anwendung von MALDI-MS zur Charakterisierung von synthetischen Polymeren" CY - Berlin, Germany DA - 1999-05-17 PY - 1999 AN - OPUS4-11301 LA - deu 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 - CONF A1 - Falkenhagen, Jana A1 - Krüger, Ralph-Peter A1 - Schulz, Günter A1 - Weidner, Steffen T1 - Polymer characterization by LC / MALDI-MS coupling T2 - Bayreuther Polymer Symposium 2001 CY - Bayreuth, Germany DA - 2001-09-16 PY - 2001 CY - Bayreuth AN - OPUS4-2256 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weidner, Steffen T1 - Erste Untersuchungen zur Infrarot-MALDI-MS von Polymeren T2 - II. BAM-Kolloquium zu "Anwendung von MALDI-MS zur Charakterisierung von synthetischen Polymeren" CY - Berlin, Germany DA - 1998-05-04 PY - 1998 AN - OPUS4-11281 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -