TY - JOUR A1 - Zorn, R. A1 - Yin, Huajie A1 - Lohstroh, W. A1 - Harrison, W. A1 - Budd, P.M. A1 - Pauw, Brian Richard A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity - the Boson peak of PIM-1 JF - Physical Chemistry Chemical Physics N2 - Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, the vibrational density of states (VDOS) for PIM-1, the prototypical polymer with intrinsic microporosity, is investigated by means of inelastic neutron scattering. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid). The measured data show the characteristic low frequency excess contribution to VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. In comparison to the Boson peak of Matrimid, that of PIM-1 is shifted to lower frequencies. This shift is discussed considering the microporous, sponge-like structure of PIM-1 as providing a higher compressibility at the molecular scale than for conventional polymers. For an annealed PIM-1 sample, the Boson peak shifts to higher frequencies in comparison to the un-annealed sample. These changes in the VDOS of the annealed PIM-1 sample are related to changes in the microporous structure as confirmed by X-ray scattering. KW - Polymers KW - Boson peak KW - Neutron scattering KW - Physical aging KW - Polymer of intrinsic microporosity PY - 2018 DO - https://doi.org/10.1039/C7CP07141H SN - 1463-9076 SN - 1463-9084 VL - 20 IS - 3 SP - 1355 EP - 1363 PB - The Royal Society of Chemistry AN - OPUS4-43808 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - Chua, Y. Z. A1 - Yang, B. A1 - Schick, C. A1 - Harrison, W. A1 - Budd, P. A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - First clear cut experimental evidence for a glass transition in a polymer with intrinsic microporosity: PIM-1 JF - Journal Physical Chemistry Letters N2 - Polymers with intrinsic microporosity (PIMs) represent a novel, innovative class of materials with great potential in various applications from high-performance gas separation membranes to electronic devices. Here for the first time, for PIM-1, as the archetypal PIM, fast scanning calorimetry provides definitive evidence for a glass transition (Tg=715 K, heating rate 3·10^4 K/s) by decoupling the time-scales responsible for glass transition and decomposition. As the rigid molecular structure of PIM-1 prevents any conformational changes, small-scale bend and flex fluctuations must be considered the origin of its glass transition. This result has strong implications for the fundamental understanding of the glass transition and for the physical aging of PIMs and other complex polymers, both topical problems of materials science. KW - Polymers with intrinsic microporosity KW - Fast Scanning Calorimetry PY - 2018 DO - https://doi.org/10.1021/acs.jpclett.8b00422 SN - 1948-7185 VL - 9 IS - 8 SP - 2003 EP - 2008 PB - ACS AN - OPUS4-44683 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -