TY - CONF A1 - Yin, Huajie T1 - Calorimetric Glass Transition of Ultrathin Films of Homopolymers and Their Blends T2 - DPG Frühjahrstagung CY - Regensburg, Germany DA - 2013-03-10 PY - 2013 AN - OPUS4-28762 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - Schönhals, Andreas T1 - Calorimetric glass transition of ultrathin poly(vinyl methyl ether) films N2 - Specific heat spectroscopy in the frequency range typically from 1 Hz to 1 kHz with a sensitivity of pJ/K was employed to study the glass transition behavior of ultrathin poly(vinyl methyl ether) (PVME) films with thicknesses ranging from 218 nm down to 12 nm. The amplitude and the phase angle of the complex differential voltage as a measure of the complex heat capacity were obtained as a function of temperature at a given frequency simultaneously. Both spectra are used to determine the dynamic glass transition temperature as a function of both the frequency and the film thickness. As main result no thickness dependence of the dynamic glass transition temperature was observed down to a film thickness of 12 nm within the experimental uncertainty of ±2 K. Further the width of the glass transition is independent of the film thickness which indicates that the extent of the cooperativity is essentially smaller than 12 nm. KW - Specific heat spectroscopy KW - Dynamic glass transition KW - Poly(vinyl methyl ether) PY - 2013 DO - https://doi.org/10.1016/j.polymer.2013.02.025 SN - 0032-3861 SN - 1873-2291 VL - 54 IS - 8 SP - 2067 EP - 2070 PB - Springer CY - Berlin AN - OPUS4-28011 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yin, Huajie T1 - Glass Transition of Ultrathin Films of Homopolymers and Polymer Blend Investigated by Dielectric Relaxation and Specific Heat Spectroscopy T2 - Kolloqiumsvortrag, Helmholtz-Zentrum Geesthacht CY - Geesthacht, Germany DA - 2013-06-21 PY - 2013 AN - OPUS4-28705 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - Cangialosi, D. A1 - Schönhals, Andreas T1 - Glass transition and segmental dynamics in thin supported polystyrene films: The role of molecular weight and annealing N2 - Broadband dielectric spectroscopy (BDS), specific heat spectroscopy (HCS) and capacitive scanning dilatometry (CSD) are used to study the glass transition and segmental dynamics in thin supported polystyrene (PS) films. Different molecular weights (Mw = 50 kg/mol, Mw = 260 kg/mol, Mw = 1408 kg/mol) and annealing protocols are employed in the study. The segmental dynamics is independent of the film thickness for each Mw in the temperature window of the dielectric measurement. The thermal glass transition temperature, Tg, measured by CSD depends on the film thickness and shows also a dependence on Mw. These observations are explained in terms of the formation of irreversibly adsorbed layer due to chain adsorption on the Al substrates during annealing. KW - Thin polystyrene films KW - Glass transition KW - Segmental dynamics PY - 2013 DO - https://doi.org/10.1016/j.tca.2013.05.034 SN - 0040-6031 SN - 1872-762X VL - 566 SP - 186 EP - 192 PB - Elsevier CY - Amsterdam AN - OPUS4-28736 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Emamverdi, Farnaz A1 - Yin, Huajie A1 - Smales, Glen Jacob A1 - Harrison, W. J. A1 - Budd, P. M. A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Polymers of intrinsic microporosity - Molecular mobility and physical aging revisited by dielectric spectroscopy and X‑ray scattering N2 - Polymers of intrinsic microporosity (PIMs) are promising candidates for the active layer in gas separation membranes due to their high permeability and reasonable permselectivity. These appealing properties originate from a microporous structure as a result of inefficient segment packing in the condensed state due to a combination of a ladder-like rigid backbone and sites of contortion. However, this class of polymers suffers from a significant decrease in the permeability with time due to physical aging, whereby typically, the permselectivity increases. The initial microporous structures approach a denser state via local rearrangements, leading to the reduction of the permeability. Hence, a detailed characterization of the molecular mobility in such materials can provide valuable information on physical aging. In this work, the dielectric behavior of PIM-1 films and their behavior upon heating (aging) were revisited by isothermal frequency scans during different heating/cooling cycles over a broad temperature range between 133 and 523 K (−140 to 250 °C). In addition, the obtained results were compared with data of samples that were annealed at ambient temperatures over different time scales. Multiple dielectric processes were observed: several relaxation processes due to local fluctuations and a Maxwell−Wagner−Sillars polarization effect related to the microporosity. The temperature dependence of the rates of all processes follows the Arrhenius law where the estimated activation energy depends on the nature of the process. The influence of the thermal history (aging) on the processes is discussed in detail. KW - Polymers of intrinsic microporosity PY - 2022 DO - https://doi.org/10.1021/acs.macromol.2c00934 VL - 55 SP - 7340 EP - 7350 PB - American Chemical Society CY - Washington, DC AN - OPUS4-55485 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yin, Huajie T1 - Molecular mobility of super glassy polymers for gas separation membranes investigated by dielectric spectroscopy N2 - Super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP) or polymers with intrinsic microporosity (PIMs) play an important role in the current development of membrane materials for gas separation because of their high permeability and selectivity. Unfortunately, such materials which have a high fractional free volume (FFV) are prone to pronounced physical aging. The initial microporous structures approach a more dense state via local chain rearrangements which results in a dramatic reduction in the gas permeability. For the first time, broadband dielectric spectroscopy was employed to investigate the molecular dynamics of two representative groups of super glassy polymers: PIMs (PIM-1 & PIM-EA-TB) and Si-containing polynobornenes (PTCNSi1 & PTCNSi2). The dielectric behavior of the solution-cast polymeric films was measured by isothermal frequency scans during the different heating cycles in a broad temperature range. Structural relaxation of the films was observed during the measurements. Molecular relaxation processes following Arrhenius behavior with unusually high activation energies were observed for all the investigated polymers. The PIMs showed furthermore a significant conductivity in the glassy state which is explained with the formation of local intermolecular agglomerated structures due to interaction of π-electrons in aromatic moieties of the polymer backbone. T2 - 8th International Discussion Meeting on Relaxations in Complex Systems CY - Wisla, Poland DA - 23.07.2017 KW - Broadband dielectric spectroscopy KW - Molecular mobility KW - Physical aging KW - Membranes KW - Gas separation PY - 2017 AN - OPUS4-41162 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yin, Huajie T1 - Molecular Mobility and Physical aging of SuperGlassy Polymers for Gas Separation Membranes as revealed by Dielectric Spectroscopy N2 - Polymeric membranes represent a cost- and energy efficient solution for gas separation. Recently superglassy polymers with high free volume outperform many conventional dense polymers in terms of gas permeability and selectivity. However, such materials with a high fractional free volume (FFV) are prone to pronounced physical aging. The initial microporous structures approach a denser state via local chain rearrangements which results in a dramatic reduction in the gas permeability. For the first time, dielectric spectroscopy with state-of-the-art high-resolution analyzers was employed to investigate the molecular mobility and physical aging of two representative groups of superglassy polymers: PIMs (PIM-1 & PIM-EA-TB) and Si-containing polynobornenes (PTCNSi1 & PTCNSi2). The dielectric behavior of the solution-cast polymeric films was measured by isothermal frequency scans during the different heating cycles in a broad temperature range. Structural relaxation of the films was observed during the measurements. Multiple dielectric processes following Arrhenius behavior were observed for all the investigated polymers. Moreover, they all showed conductivity in the glassy state. The significant increase in the conductivity with increasing temperature especially for PIMs is explained in terms of the formation of local intermolecular agglomerated structures due to interaction of π-electrons in aromatic moieties of the polymer backbone. T2 - 8th International Conference on Advanced Fibers and Polymer Materials CY - Shanghai, China DA - 08.10.2017 KW - Physical aging KW - Membranes KW - Broadband dielectric spectroscopy KW - Gas separation KW - Molecular mobility PY - 2017 AN - OPUS4-42877 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Yin, Huajie T1 - Thermal and Dynamic Glass Transition in Ultrathin Films of Homopolymers and a Miscible Polymer Blend N2 - Dünne Polymerschichten im nanoskaligen Bereich finden heute in vielen Gebieten z. B. für Beschichtungen, als Membranen, für Sensoren oder in diversen elektronischen Geräten ihre Anwendung. Wissenschaftliche Studien belegen, dass viele physikalische Eigenschaften (Glasübergang, Kristallisation, Entnetzung, Alterung etc.) von ultradünnen Polymerschichten (Polymere in 1-dimensionaler räumlicher Begrenzung) stark von dem Verhalten im Volumen abweichen. Da die Eigenschaften eng mit der Verwendung und Funktionalität von Polymeren verknüpft sind, müssen die beobachteten Unterschiede in nanoskaliger Begrenzung genauer untersucht werden. Die vorliegende Arbeit beschäftigt sich damit, wie die Oberfläche (Luft-Polymer- Grenzfläche), die Polymer-Substrat-Wechselwirkung und die Schichtdicke die Glasübergangstemperatur (Tg) und die segmentale Dynamik (α-Relaxationsprozess) in Homopolymeren und mischbaren Polymer-Blends in dünnen Schichten beeinflussen. Komplementäre experimentelle Methoden, wie Differential Scanning Calorimetry (DSC), Capacitive Scanning Dilatometry (CSD), Breitbandige Dielektrische Spektroskopie (BDS) und Spezifische Wärme Spektroskopie (SHS) wurden angewendet, um den Glasübergang der dünnen Polymerschichten aus der thermodynamischen und kinetischen Sicht zu untersuchen. In dieser Arbeit werden die Glasübergangstemperatur und die segmentale Dynamik von ultradünnen Polymerschichten in Abhängigkeit der Schichtdicke untersucht. Für ultradünne Polycarbonatschichten (PC-Schichten, dünner als 20 nm) zwischen zwei Aluminiumschichten wurde ein Anstieg von der Glasübergangstemperatur (Tg) als auch der Vogel Temperatur (T0) mit abnehmender Schichtdicke beobachtet. BDS-Messungen zeigten einen Anstieg der segmentalen Relaxationszeit für ultradünne PC-Schichten. In den SHS-Messungen für die Siliciumdioxid (10-192 nm) basierten PC-Schichten konnte unter Einbeziehung des experimentellen Fehlers keine Abhängigkeit der segmentalen Dynamik von der Schichtdicke festgestellt werden. Diese Eigenschaften werden im Hinblick auf die Geometrie der dünnen Schichten und die relevanten Wechselwirkungsenergien zwischen dem Polymer und dem Substrat diskutiert. Im Falle von dünnen Polystyrolschichten (PS-Schichten) mit hohem Molekulargewicht (Mw) sinkt die Glasübergangstemperatur Tg mit Verringerung der Schichtdicke. Die segmentale Dynamik hängt jedoch nicht von der Stärke der Schichtdicke ab. Darüber hinaus werden für dünne PS-Schichten die Auswirkungen des Molekulargewichts Mw und Temperbedingungen auf Tg und die segmentale Dynamik untersucht. Im Bereich der dünnen Polyvinylmethyletherschichten (PVME-Schichten) konnte mittels SHS keine Abhängigkeit der segmentalen Dynamik von der Schichtdicke aufgezeigt werden. Der letzte Teil dieser Arbeit beschäftigt sich mit dünnen Schichten mischbarer Polymer-Blends mit einem Gewichtsteil von 50/50 PS/PVME. Es wurde eine Beschleunigung der segmentalen Dynamik mit geringerer Schichtdicke beobachtet. Dieses Phänomen wird mit der Oberflächenanreicherung von PVME, welches eine niedrigere Oberflächenenergie als PS aufweist, in das Polymer-Blend-System erklärt. Die segmentale Dynamik der mit PVME angereicherten freien Oberflächenschicht ist schneller als die Volumen- Dynamik. Durch die Verringerung der Schichtdicke werden diese freien Oberflächeneffekte so dominant, dass sie die gesamte segmentale Dynamik der Schichten von SHS (differenzieller AC Chip- basierten Kalorimetrie) erkennbare beeinflussen. Mittels Röntgenphotoelektronenspektroskopie (XPS) konnte die Oberflächenzusammensetzung des Films ermittelt und so die Phänomene der Oberflächenanreicherung verifiziert werden. N2 - Nowadays nanoscale thin polymer films are widely used in many fields like coatings, membranes, sensors, electronic devices and so on. Meanwhile, a lot of research work has evidenced the fact that many physical properties (glass transition, crystallization, dewetting, physical aging, etc.) of ultrathin polymer films show strong deviations from their bulk behavior. Since the aforementioned properties of polymer are closely related to their application and functionality, the discrepancies motivated us to obtain a more complete understanding of how nanoscale confinement affects the physical properties of polymer. The research work presented in this thesis is focused on understanding how the free surface (air- polymer interface), the polymer-substrate interface and the film thickness influence the glass transition temperature (Tg) and the related segmental dynamics (α-relaxation process) in both homopolymers and miscible polymer blends of thin films. Complementary experimental techniques including Differential Scanning Calorimetry (DSC), Capacitive Scanning Dilatometry (CSD), Broadband Dielectric Spectroscopy (BDS) and Specific Heat Spectroscopy (SHS) have been used to investigate the glass transition of thin polymer films from both the thermodynamic and the kinetic point of view. In the thesis the film thickness dependence of Tg and segmental dynamics of different thin polymer films have been investigated. For ultrathin polycarbonate (PC) films capped between two aluminum (Al) layers an increase of both the glass transition temperature (Tg) and Vogel temperature (T0) with decreasing film thickness (d) was observed when the thickness became lower than 20 nm. The segmental relaxation time at a fixed temperature was found to increase for the ultrathin PC film of 19 nm measured by BDS, whereas no thickness dependency of the segmental dynamics was detected within the experimental error limit for the PC films supported on silicon dioxide (SiO2) (10-192 nm) in the SHS measurements. These properties are discussed in terms of the thin film geometry and the relevant interfacial interaction between the polymer and the substrate. In the case of thin polystyrene (PS) films with high molecular weight (Mw), Tg is decreasing with reducing film thickness while the segmental dynamics is independent of film thickness. Moreover, the effects of the Mw and the annealing protocol performed on thin PS films on their Tg and segmental dynamics is studied. In the part of thin poly(vinyl methyl ether) (PVME) films, no thickness dependence of the segmental dynamics was observed in the SHS measurements. The last part of the thesis was concentrated on the thin films of a miscible polymer blend, PS/PVME with the weight fraction of 50/50. It was observed that the segmental dynamics became faster with reducing the film thickness. This phenomenon is explained in terms of surface enrichment of PVME in the polymer blend system where PVME has a lower surface energy than PS. The segmental dynamics of the PVME-enriched free surface layer are faster than the bulk dynamics. Such free surface effect becomes so predominant with reducing the film thickness that it affects the segmental dynamics of the whole films detected by SHS using differential AC chip-based calorimetry. X-ray photoelectron spectroscopy (XPS) was used to probe the surface composition in order to confirm such surface enrichment phenomena. T3 - BAM Dissertationsreihe - 117 KW - glass transition KW - specific heat spectroscopy KW - ultrathin film KW - polymer KW - broadband dielectric spectroscopy PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-418 SN - 978-3-9816380-5-9 SN - 1613-4249 VL - 117 SP - 1 EP - 133 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-41 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 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 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 -