TY - JOUR A1 - Kricheldorf, H.R. A1 - Weidner, Steffen A1 - Scheliga, F. A1 - Lahcini, M. T1 - Poly(epsilon-caprolactone) by combined ring-opening polymerization and polycondensation N2 - Numerous water-initiated polymerizations of εCL are conducted in bulk with variation of catalyst, reaction time, and temperature. The conversions are determined by 1H NMR and the molar masses by SEC measurements. For polymerizations at 100 °C, Bi triflate and Hf triflate are used as catalysts, whereas at 140 °C, Al triflate, Sn(II) triflate, SnCl2, HfCl4, BiCl3, and LaCl3 are used. In addition to a closed reaction vessel, experiments are also performed with stirring in a vacuum. Under these conditions, the best catalyst (SnCl2) yields 2–3 times higher molar masses and mass spectra indicate a significant higher fraction of cyclic polymers. The results prove that a modification of the procedure may stimulate a polycondesation process without change of catalyst, time, and temperature. KW - Epsilon-Caprolactone KW - Cyclization KW - MALDI-TOF mass spectrometry KW - Polycondensations KW - Ring-opening polymerizations PY - 2012 U6 - https://doi.org/10.1002/macp.201200061 SN - 1022-1352 SN - 1521-3935 VL - 213 IS - 14 SP - 1482 EP - 1488 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-26273 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Weidner, Steffen A1 - Scheliga, F. T1 - Poly(Epsilon-caprolactone) by combined ring-opening polymerization and azeotropic polycondensation - the role of cyclization and equilibration N2 - Using three different catalysts, water-initiated polymerizations of ε-caprolactone were conducted in bulk with variation of the monomer/water ratio. The resulting CH2OH and CO2H- terminated polylactones were subjected in situ to azeotropic polycondensations. With Bi-triflate and temperatures, the polycondensations were not much successful and involved side reactions. With ZnCl2, and especially SnCl2, considerably higher molar masses were achieved. The substitution of toluene for chlorobenzene for refluxing gave better results. The polycondensations broadened the molar mass distribution of the ROP-based prepolymers, and polydispersities between 1.4–1.8 were obtained. The MALDI–TOF mass spectra revealed that the polycondensations significantly enhanced the fraction of rings due to efficient 'end-biting' reactions. By comparison with copolymerization experiments and Sn methoxide-initiated polymerizations, it was demonstrated that equilibration reactions, such as the formation of rings by 'back-biting,' did not occur. KW - Ring-opening polymerization KW - Epsilon-caprolactone (e-CL) KW - Cyclization KW - MALDI-TOF mass spectrometry KW - Polycondensation KW - Polyesters PY - 2012 U6 - https://doi.org/10.1002/pola.26222 SN - 0360-6376 SN - 0887-624X VL - 50 IS - 20 SP - 4206 EP - 4214 PB - Wiley CY - Hoboken, NJ AN - OPUS4-26500 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Falkenhagen, Jana A1 - Bressler, I. T1 - Copolymer composition determined by LC-MALDI-TOF MS coupling and 'MassChrom2D' data analysis N2 - The MALDI-TOF MS analysis of copolymers very often results in complex spectra. A chromatographic separation/fractionation prior to the MALDI investigation can be advantageous since the MALDI mass spectra of fractions very often reveal well-resolved peaks of distinguishable copolymer series. For this purpose, different modes of chromatography have been applied. Chromatographic runs were transferred to MALDI targets utilizing a combined air/electrospray deposition device. Using the new MassChrom2D software, fraction-dependent 2D copolymer compositions plots were obtained providing additional information on the chromatographic mode, and enabling fast modification of conditions to increase separation. KW - Copolymer composition KW - Chromatography KW - Coupling KW - MALDI-TOF mass spectrometry PY - 2012 U6 - https://doi.org/10.1002/macp.201200169 SN - 1022-1352 SN - 1521-3935 VL - 213 IS - 22 SP - 2404 EP - 2411 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-27270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -