TY - JOUR A1 - Krüger, Ralph-Peter A1 - Much, Helmut A1 - Schulz, Günter A1 - Rikowski, E. T1 - Zur Charakterisierung von Si-Polymeren durch flüssigchromatographische Verfahren in Kopplung mit der MALDI-TOF-MS N2 - Summary. The coupling of the three liquid chromatographic modes with MALDI-TOF mass spectrometry is suitable for the determination of the molecular, functional, and chemical heterogeneities of Si polymers. Silsesquioxanes and siloxanes serve as examples for this method of structure identification. The substance specific construction of the SEC calibration curve by means of MALDI-MS is shown. Zusammenfassung. Die Kopplung der drei flüssigchromatographischen Modi mit MALDI-TOF-Massenspektrometrie ist zur Bestimmung der molekularen, funktionalen und chemischen Verteilungen von Si-Polymeren geeignet. Silsesquioxane und Siloxane dienen als Beispiele für diese Art der Strukturerkennung. Die substanzspezifische Konstruktion einer SEC-Eichkurve mit Hilfe der MALDI-MS wird gezeigt. KW - Si polymer characterization KW - LC/MALDI-TOF-MS PY - 1999 DO - https://doi.org/10.1007/PL00010162 SN - 0026-9247 SN - 1434-4475 VL - 130 IS - 1 SP - 163 EP - 174 PB - Springer CY - Wien AN - OPUS4-2163 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Eggerstedt, S. A1 - Krüger, Ralph-Peter T1 - Macrocycles, 6a / MALDI-TOF mass spectrometry of tin-initiated macrocyclic polylactones in comparison to classical mass-spectroscopic methods PY - 1999 SN - 1022-1352 SN - 1521-3935 VL - 200 IS - 6 SP - 1284 EP - 1291 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-2166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. A1 - Hauser, K. A1 - Krüger, Ralph-Peter A1 - Schulz, Günter T1 - Macrocycles 12. Ring-Opening Polycondensations of Tin-Containing Macrocycles with Bis(Thioarylester)s N2 - 2,2-Dibutyl-2-stanna-1,3-dioxepane (DSDOP) was polycondensed with bis(4-chlorothiophenyl) suberat under various reaction conditions, but only moderate molecular weights (Mn 10000) were obtained. The MALDI-TOF mass spectrosmetry revealed the formation of cyclic oligo- and polyesters in addition to linear species having OH, CO2H, and unreacted 4-chlorothiophenyl ester endgroups. Furthermore, -Caprolactone (-CL) was polymerized with DSDOP as the initiator at monomer/initiator (M/I) ratios of 20 and 50. The resulting tin-containing macrocyclic polylactones were reacted with sebacic acid bis(4-thiocresyl)ester at three different temperatures and with different reaction times. Analogous polycondensations were conducted with suberic acid bis(4-chlorothiophenyl) ester. The presence of thioarylester endgroups in the isolated polyesters was checked by 1H NMR spectroscopy. The highest conversions were found at long reaction times (24 or 72 hours), or after the addition of pyridine and N,N-dimethylaminopyridine as catalysts. Despite high conversions, the number average molecular weights (Mn's) did not exceed values around 20000. Even in the samples having the highest molecular weights, unreacted 4-chlorothiophenylester endgroups were detected by GPC measurements evaluated with a UV-detector. It is concluded that both factors, cyclization and incomplete conversion, contribute to the limitation of the chain growth. KW - Ring-Opening Polycondensations KW - Macrocycles KW - Polyesters PY - 2000 DO - https://doi.org/10.1081/MA-100101099 SN - 1060-1325 SN - 1520-5738 VL - 37 IS - 4 SP - 379 EP - 394 PB - Taylor & Francis CY - Philadelphia, PA AN - OPUS4-2167 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. A1 - Probst, N. A1 - Schwarz, G. A1 - Schulz, Günter A1 - Krüger, Ralph-Peter T1 - New Polymer Syntheses - 107. Aliphatic Poly(thio ester)s by Ring-Opening Polycondensation of 2-Stanna-1,3-Dithiacycloalkanes N2 - We prepared 2,2-dibutyl-2-stanna-1,3-dithiacycloalkanes from dibutyltin oxide and ,-dimercaptoalkanes. Heterocycles with five-, six-, seven-, or nine-ring members were used as bifunctional monomers for polycondensations with aliphatic dicarboxylic acid chlorides. These polycondensations conducted in bulk were highly exothermic and yielded poly(thio ester)s with number average molecular weights (Mn's) in the range of 5000-30,000 Da. These poly(thio ester)s proved to be rapidly crystallizing materials with melting temperatures in the range of 90-150 °C. In addition to the success of the new synthetic approach, two interesting and unpredictable results were obtained. All volatile species detectable by matrix assisted laser desorption induced-time of flight (MALDI-TOF) mass spectrometry were cyclic oligo- and poly(thio ester)s. Second, several polyesters showed a reversible first-order change of the crystal modification as identified by differential scanning calorimetry measurements and X-ray scattering with variation of the temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3656-3664, 2000 KW - Poly(thio-ester)s KW - Ring-opening polycondensation KW - Macrocycles KW - Change of crystal structure PY - 2000 DO - https://doi.org/10.1002/1099-0518(20001001)38:19<3656::AID-POLA190>3.0.CO;2-M SN - 0360-6376 SN - 0887-624X VL - 38 IS - 19 SP - 3656 EP - 3664 PB - Wiley CY - Hoboken, NJ AN - OPUS4-2170 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Spickermann, J. A1 - Martin, K. A1 - Räder, H.J. A1 - Müllen, K. A1 - Schlaad, H. A1 - Müller, A. H. E. A1 - Krüger, Ralph-Peter T1 - Quantitative analysis of broad molecular weight distributions obtained by MALDI-TOF mass spectrometry PY - 1996 SN - 1469-0667 SN - 1356-1049 SN - 1365-0718 IS - 2 SP - 161 EP - 165 PB - IM Publications CY - Chichester AN - OPUS4-2153 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wachsen, O. A1 - Reichert, K.H. A1 - Krüger, Ralph-Peter A1 - Much, Helmut A1 - Schulz, Günter T1 - Thermal decomposition of biodegradable polyesters - III. Studies on the mechanisms of thermal degradation of oligo-L-lactide using SEC, LACCC and MALDI-TOF-MS PY - 1997 SN - 0141-3910 SN - 1873-2321 VL - 55 SP - 225 EP - 231 PB - Applied Science Publ. CY - London AN - OPUS4-2154 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tressl, R. A1 - Wondrak, G. T. A1 - Krüger, Ralph-Peter A1 - Rewicki, D. T1 - New Melanoidin-like Maillard Polymers from 2-Deoxypentoses KW - Maillard system 2-deoxy-D-ribose / methylamine KW - Oligomerization of N-methyl-2-hydroxymethyl(and hydroxyl[13C]methyl)pyrrole KW - Antioxidative activity KW - Model compounds for melanoidins PY - 1998 SN - 0021-8561 SN - 1520-5118 VL - 46 IS - 1 SP - 104 EP - 110 PB - American Chemical Society CY - Columbus, Ohio AN - OPUS4-2158 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tressl, R. A1 - Wondrak, G. T. A1 - Garbe, L.-A. A1 - Krüger, Ralph-Peter A1 - Rewicki, D. T1 - Pentoses and Hexoses as Sources of New Melanoidin-like Maillard-Polymers KW - Model compounds for melanoidins KW - Pyrroles from pentoses and hexoses KW - Beta-dicarbonyl pathway of the Maillard reaction KW - Polycondensation KW - MALDI-TOF-MS analysis KW - Antioxidative activity of oligomeric model compounds PY - 1998 SN - 0021-8561 SN - 1520-5118 VL - 46 IS - 5 SP - 1765 EP - 1776 PB - American Chemical Society CY - Columbus, Ohio AN - OPUS4-2159 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Veith, M. A1 - Elsässer, R. A1 - Krüger, Ralph-Peter T1 - Synthesis of Dendrimers with a N-Si-C Framework N2 - A novel family of air-stable dendrimers with a N-Si-C framework has been prepared up to the fourth generation. The divergent synthesis starts with the hydrosilylation of the trisilazane N(SiMe2vinyl)3 [0-G(vinyl)] by HSiMe2Cl, which gives the three-directional core molecule N(SiMe2CH2CH2SiMe2Cl)3 [0-G(Cl)]. A 1-to-2 branching achieved by reacting the core molecule [0-G(Cl)] with 3 equiv of KN(SiMe2vinyl)2 affords the first generation dendrimer [1-G(vinyl)]. By repeating the above two steps, the second [2-G(vinyl)], third [3-G(vinyl)], and fourth generation [4-G(vinyl)] can be obtained. The compounds have been characterized by 1H, 13C, and 29Si NMR spectroscopy, by elemental analysis, and up to the third generation by MALDI-TOF mass spectrometry. Gel permeation chromatography was used to prove the fourth generation [4-G(vinyl)]. PY - 1999 DO - https://doi.org/10.1021/om9807708 SN - 0276-7333 SN - 1520-6041 VL - 18 IS - 4 SP - 656 EP - 661 PB - American Chemical Society CY - Washington, DC AN - OPUS4-2162 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schlaad, H. A1 - Müller, A. H. E. A1 - Kolshorn, H. A1 - Krüger, Ralph-Peter T1 - Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls PY - 1995 SN - 0170-0839 SN - 1436-2449 VL - 35 SP - 169 EP - 176 PB - Springer CY - Berlin AN - OPUS4-2144 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Ralph-Peter A1 - Much, Helmut A1 - Schulz, Günter T1 - Determination of polymer heterogeneity by two-dimensional orthogonal liquid chromatography KW - Orthogonal chromatography KW - Size exclusion chromatography KW - Liquid adsorption chromatography at critical conditions KW - Matrix-assisted laser desorption ionization time-of-flight mass spectrometry KW - Polyester KW - Polyether PY - 1996 SN - 1023-666X SN - 1563-5341 VL - 2 SP - 221 EP - 235 PB - Gordon and Breach Publ. CY - Amsterdam AN - OPUS4-2146 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonnenschein, H. A1 - Kreher, T. A1 - Gründemann, E. A1 - Krüger, Ralph-Peter A1 - Kunath, A. A1 - Zabel, V. T1 - Novel Redox-Active Cyclophanes Based on 3,3'-Bisindolizines - Synthesis and Chirality PY - 1996 SN - 0022-3263 SN - 1520-6904 VL - 61 SP - 710 EP - 714 PB - American Chemical Society CY - Washington, DC AN - OPUS4-2147 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leukel, J. A1 - Burchard, W. A1 - Krüger, Ralph-Peter A1 - Much, Helmut A1 - Schulz, Günter T1 - Mechanism of the anionic copolymerization of anhydride- cured epoxies-analysisted by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) PY - 1996 SN - 1022-1336 SN - 1521-3927 VL - 17 SP - 359 EP - 366 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-2148 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gähde, J. A1 - Mix, Renate A1 - Krüger, Ralph-Peter A1 - Goering, Harald A1 - Funke, W. A1 - Hermann, U. T1 - Adherence of Liquid Crystalline TDI-Polyurethanes to Steel KW - Main-chain liquid crystalline polyurethanes KW - Primer on steel KW - Pull-off test KW - Wet adhesion of alkyd melamine resin KW - Mesogenic unit KW - Glass transition temperature KW - Hard segments KW - Soft segments PY - 1996 SN - 0021-8464 SN - 1545-5823 VL - 58 SP - 243 EP - 251 PB - Gordon & Breach CY - New York, NY AN - OPUS4-2152 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Vakhtangishvili, L. A1 - Schwarz, G. A1 - Krüger, Ralph-Peter T1 - Cyclic Hyperbranched Poly(ether ketone)s Derived from 3,5-Bis(4-fluorobenzoyl)phenol N2 - 3,5-Bis(4-fluorobenzoyl)phenol was polycondensed under various reaction conditions. Low molecular weights were obtained (Mn < 8000 Da), and MALDI-TOF mass spectrometry indicated that the chain growth was limited by cyclization. In the best mass spectra the cyclic, hyperbranched poly(ether ketone)s were detectable up to masses around 14 000 Da. When 4,4'-difluordiphenyl sulfone was added, star-shaped polymers having a diphenyl sulfone star center were formed, but cyclization was not completely suppressed. The results were compared to those obtained from "linear polycondensations" based on 4,4'-difluorobenzophenone (DFBP) and 4-tert-butylcatechol or bisphenol A. The poly(ether ketone)s of DFBP had also low molecular weights and contained high fractions of cycles. It is concluded that also in the case of hyperbranched polymers cyclization competes with propagation at any stage of the polycondensation at any concentration. Therefore, the fundamental trend of any "abn" polycondensation is the formation of star-shaped polymers having a cyclic core and hyperbranched star arms. PY - 2003 DO - https://doi.org/10.1021/ma021799x SN - 0024-9297 SN - 1520-5835 VL - 36 SP - 5551 EP - 5558 PB - American Chemical Society CY - Washington, DC AN - OPUS4-2622 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Vakhtangishvili, L. A1 - Schwarz, G. A1 - Schulz, Günter A1 - Krüger, Ralph-Peter T1 - Macrocycles 25. Cyclic poly(ether sulfone)s derived from 4-tert-butylcatechol N2 - Poly(ether sulfone)s were prepared by polycondensation of silylated 4-tert-butylcatechol and 4,4?-difluorodiphenylsulfone in N-methylpyrrolidone. The feed ratio and the reaction time were varied to study the influence of stoichiometry and conversion on molecular weight and extent of cyclization. Molecular weights and molecular weight distributions (MWD)s were characterized by SEC measurements calibrated with polystyrene. Light scattering confirmed that calibration with polystyrene gives reasonable results and revealed a tendency towards a bimodal MWD for the samples rich in cycles. The MALDI-TOF mass spectrometry indicated that the extent of cyclization increased with higher conversion and with optimization of the stoichiometry. This interpretation was confirmed by 1H NMR endgroup analyses. For the samples with the highest molar masses only mass peaks of cycles were found, which were detectable up to 20 000 Da before and up to 27 000 Da after fractionation. Via the pseudo-high dilution method low molar mass poly(ether sulfone) containing more than 95 mol% of cycles were prepared, and even these low molar mass samples had broad MWDs. DSC measurements indicated that the glass transition temperatures depend on the structure of the endgroups and increase with higher fractions of cycles. KW - Poly(ether sulfone)s KW - Polycondensation KW - MALDI-TOF mass spectrometry PY - 2003 DO - https://doi.org/10.1016/S0032-3861(03)00410-5 SN - 0032-3861 SN - 1873-2291 VL - 44 SP - 4471 EP - 4480 PB - Springer CY - Berlin AN - OPUS4-2623 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shaik, A.-A. A1 - Richter, M. A1 - Kricheldorf, H. A1 - Krüger, Ralph-Peter T1 - New polymer syntheses - CIX. Biodegradable, alternating copolyesters of terephthalic acid, aliphatic dicarboxylic acids, and alkane diols N2 - Copolyesters with an alternating sequence of terephthalic acid and aliphatic dicarboxylic acids were prepared with three different methods. First, dicarboxylic acid dichlorides were reacted with bis(2-hydroxyethyl)terephthalate (BHET) in refluxing 1,2-dichlorobenzene. Second, the same monomers were polycondensed at 0-20 °C in the presence of pyridine. Third, dicarboxylic acid dichlorides and silylated BHET were polycondensed in bulk. Only this third method gave satisfactory molecular weights. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry revealed that the copolyesters prepared by the pyridine and silyl methods might have contained considerable fractions of cyclic oligoesters and polyesters despite the absence of transesterification and backbiting processes. The alternating sequences and thermal properties were characterized with 1H NMR spectroscopy and differential scanning calorimetry measurements, respectively. In agreement with the alternating sequence, all copolyesters proved to be crystalline, but the crystallization was extremely slow [slower than that of poly(ethylene terephthalate)]. A second series of alternating copolyesters was prepared by the polycondensation of silylated bis(4-hydroxybut- yl)terephthalate with various aliphatic dicarboxylic acid dichlorides. The resulting copolyesters showed significantly higher rates of crystallization, and the melting temperatures were higher than those of the BHET-based copolyesters. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3371-3382, 2001 KW - Poly(ethylene terephthalate) KW - Poly(butylene terephthalate) KW - Alternating sequence KW - Macrocycles KW - Crystallization KW - Biodegradable polyesters PY - 2001 DO - https://doi.org/10.1002/pola.1320 SN - 0360-6376 SN - 0887-624X VL - 39 IS - 19 SP - 3371 EP - 3382 PB - Wiley CY - Hoboken, NJ AN - OPUS4-2173 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bünger, H. A1 - Krüger, Ralph-Peter A1 - Pietschmann, S. A1 - Wüstneck, N. A1 - Kaufner, L. A1 - Tschiersch, R. A1 - Pison, U. T1 - Two hydrophobic protein fractions of ovine pulmonary surfactant: Isolation, characterisation and biophysical activity N2 - Pulmonary surfactant contains two extremely hydrophobic proteins, SP-B and SP-C. We present a novel HPLC method for the preparation of these hydrophobic proteins. It is based on size-exclusion chromatography using the apolar stationary-phase butyl silica gel and isocratic elution with acidified chloroform/methanol. Samples for HPLC were prepared from sheep lung lavage fluid by centrifugation and extraction with chloroform/methanol. Amino acid analyses of the two protein fractions revealed sequences that are consistent with SP-B and SP-C, respectively. MALDI-TOF-MS analyses of the SP-B fraction showed one major peak of dimeric SP-B with m/z 17,361, and additional peaks of monomeric and oligomeric forms, which are predominantly even numbered. The SP-C fraction showed a peak at m/z 4200, consistent with the theoretical mass of the dipalmitoylated form of this protein. The biophysical activity of pure sheep SP-B and SP-C was evaluated by measuring the surface tension using axisymmetric drop shape analysis for captive bubbles. We found distinct surface pressure versus surface area isotherms of SP-B and SP-C indicating different biophysical activities for these surfactant proteins. The new preparative HPLC method is able to replace the established, time-consuming low-pressure liquid chromatography method for the isolation of SP-B and SP-C from lipids. KW - Surfactant proteins KW - SP-B KW - SP-C KW - Preparative HPLC KW - MALDI-TOF-MS KW - Surface pressure KW - Captive bubble PY - 2001 DO - https://doi.org/10.1006/prep.2001.1510 SN - 1046-5928 SN - 1096-0279 VL - 23 IS - 2 SP - 319 EP - 327 PB - Elsevier CY - Amsterdam AN - OPUS4-2174 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Czichocki, G. A1 - Heger, R. A1 - Much, Helmut A1 - Krüger, Ralph-Peter A1 - Goedel, W.A. T1 - Synthesis of Polyisoprenes with Sulfonate Head Groups and their Purification by HPLC PY - 2001 SN - 0932-3414 SN - 0040-3490 VL - 38 IS - 3 SP - 168 EP - 172 PB - Hanser CY - München AN - OPUS4-2175 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Böhme, S. A1 - Schwarz, G. A1 - Krüger, Ralph-Peter A1 - Schulz, Günter T1 - Macrocycles 18. The Role of Cyclization in Syntheses of Poly(ether-sulfone)s N2 - Poly(ether-sulfone)s having an identical backbone were prepared by four different methods. First, silylated bisphenol A (BSBA) was polycondensed with 4,4'-difluorodiphenyl sulfone (DFDPS) and K2CO3 in N-methylpyrrolidone with variation of the temperature. Second, analogous polycondensation were conducted using CsF as catalyst (and no K2CO3). Third, CsF-catalyzed polycondensations BSBA and DFDPS were conducted in bulk up to 290 C. Fourth, free bisphenol was polycondensed with DFDPS or 4,4'-dichlorodiphenyl sulfone and K2CO3 in DMSO with azeotropic removal of water. MALDI-TOF mass spectroscopy revealed that the first method mainly yielded cyclic poly(ether-sulfone)s which were detected up to masses around 13 000 Da. These and other results suggest that these polycondensations take a kinetically kontrolled course at tempeatures 145 C. This interpretation is also valid for the fourth method where high yields of cycles were obtained with DFDPS. With the less reactive 4,4'-dichlorodiphenyl sulfone lower conversions, lower molecular weights and lower fractions of cycles were found. In contrast to KF (resulting from K2CO3) CsF cleaves the poly(ether sulfone) backbone at temperatures > 145 C. Smaller amounts of smaller cycles were found in these CsF-catalyzed polycondensations which were in this case the result of thermodynamically controlled "back-biting degradation". PY - 2001 DO - https://doi.org/10.1021/ma010218l SN - 0024-9297 SN - 1520-5835 VL - 34 SP - 8886 EP - 8893 PB - American Chemical Society CY - Washington, DC AN - OPUS4-2176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -