TY - JOUR A1 - Knappe, Patrick A1 - Bienert, Ralf A1 - Weidner, Steffen A1 - Thünemann, Andreas T1 - Characterization of poly/N-vinyl-2-pyrrolidone)s with broad size distributions N2 - We report on the characterization of the solution structure of poly(N-vinyl-2-pyrrolidone)s (PVP) by small-angle X-ray scattering (SAXS) and by online coupling of asymmetrical flow field-flow fractionation (A4F), SAXS and dynamic light scattering (DLS). The commercial products PVP K30 and PVP K90 with nominal molar masses of 40 × 103 and 360 × 103 g mol-1, respectively, were investigated separately and as binary mixture. Detailed information for all polymer fractions is available on the polymer contour lengths and the diffusion coefficients. Key areas of applications for the A4F-SAXS-DLS coupling are seen in comparison to static light scattering for polymers with radii of gyration smaller than 10 nm, for which only SAXS produces precise analytical results on the size of the polymers in solution. KW - Small-angle X-ray scattering KW - SAXS KW - Field-flow fractionation PY - 2010 U6 - https://doi.org/10.1016/j.polymer.2010.02.039 SN - 0032-3861 SN - 1873-2291 VL - 51 IS - 8 SP - 1723 EP - 1727 PB - Springer CY - Berlin AN - OPUS4-21222 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weidner, Steffen A1 - Meyer, A. A1 - Falkenhagen, Jana A1 - Kricheldorf, H. R. T1 - SnOct2-catalyzed and alcohol-initiated ROPs of L-lactide – About the influence of initiators on chemical reactions in the melt and the solid state N2 - SnOct2 (Sn(II) 2-ethylhexanoate) catalyzed ROPs of L-lactide were performed in bulk with eight different alcohols as initiators. The time was varied between 1 h and 24 h for all initiators. For two initiators the temperature was also lowered to 115 ◦C. Even-numbered chains were predominantly formed in all polymerizations at short times, but the rate of transesterification (e.g. even/odd equilibration) and the molecular weight distribution were found to depend significantly on the nature of the initiator. Observed transesterification reactions also continued in solid poly (L-lactide), and with the most active initiator, almost total equilibration was achieved even at 130 ◦C. This means that all chains including those of the crystallites were involved in transesterification reactions proceeding across the flat surfaces of the crystallites. The more or less equilibrated crystalline polylactides were characterized by DSC and SAXS measurements with regard to their melting temperature (Tm), crystallinity and crystal thickness. KW - Polylactide KW - MALDI-TOF MS KW - Crystallization KW - Catalysts KW - SAXS PY - 2021 U6 - https://doi.org/10.1016/j.eurpolymj.2021.110508 VL - 153 SP - 110508 PB - Elsevier Ltd. AN - OPUS4-52633 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -