TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. A1 - Frick, B. A1 - Zorn, R. T1 - Glassy dynamics of polymers confined to nanoporous glasses revealed by relaxational and scattering experiments N2 - The glassy dynamics of poly(propylene glycol) (PPG) and poly(dimethyl siloxane) (PDMS) confined to a nanoporous host system revealed by dielectric spectroscopy, temperature-modulated DSC and neutron scattering is compared. For both systems the relaxation rates estimated from dielectric spectroscopy and temperature-modulated DSC agree quantitatively indicating that both experiments sense the glass transition. For PPG the segmental dynamics is determined by a counterbalance of adsorption and confinement effect. The former results form an interaction of the confined macromolecules with the internal surfaces. A confinement effect originates from an inherent length scale on which the underlying molecular motions take place. The increment of the specific-heat capacity at the glass transition vanishes at a finite length scale of 1.8 nm. Both results support the conception that a characteristic length scale is relevant for glassy dynamics. For PDMS only a confinement effect is observed which is much stronger than that for PPG. Down to a pore size of 7.5 nm, the temperature dependence of the relaxation times follows the Vogel-Fulcher-Tammann dependence. At a pore size of 5 nm this changes to an Arrhenius-like behaviour with a low activation energy. At the same pore size vanishes for PDMS. Quasielastic neutron scattering experiments reveal that also the diffusive character of the relevant molecular motions --found to be characteristic above the glass transition-- seems to disappear at this length scale. These results gives further strong support that the glass transition has to be characterised by an inherent length scale of the relevant molecular motions. KW - Glass transitions KW - Dielectric loss and relaxation KW - Macromolecular and polymer solutions KW - Polymer melts KW - Swelling PY - 2003 DO - https://doi.org/10.1140/epje/i2003-10036-4 SN - 1292-8941 SN - 1292-895X VL - 12 IS - 1 SP - 173 EP - 178 PB - EDP Sciences CY - Orsay AN - OPUS4-2866 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Frick, B. A1 - Schönhals, Andreas A1 - Zorn, R. A1 - Alba-Simionesco, C. A1 - Dosseh, G. A1 - LeQuellec, C. T1 - Inelastic neutron scattering probing the dynamics of glass forming systems in confinement - recent results on organic liquids and polymers T2 - 3th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Delft, Netherlands DA - 2004-08-23 PY - 2004 AN - OPUS4-3903 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. A1 - Frick, B. A1 - Zorn, R. ED - Fourkas, J. T. T1 - Poly(methyl phenyl siloxane) in random nanoporous glasses - molecular dynamics and structure N2 - The effect of a nanometer confinement on the molecular dynamics of poly(methyl phenyl siloxane) (PMPS) was studied by dielectric spectroscopy (DK), temperature modulated DSC (TMDSC) and neutron scattering (NS). DK and TMDSC experiments show that for PMPS in 7.5 nm pores the molecular dynamics is faster than in the bulk which originates from an inherent length scale of the underlying molecular motions. At a pore size of 5 nm the temperature dependence of the relaxations times changes from a Vogel-Fulcher-Tammann like behavior to an Arrhenius one. At the same pore size Dcp vanishes. These results give strong support that the glass transition has to be characterized by an inherent length scale of the relevant molecular motions. Quasielastic neutron scattering experiments reveal a strong change even in the microscopic dynamic. T2 - Symposium P: "Dynamics in Small Confining Systems VII" ; MRS fall meeting 2004 CY - Boston, MA, USA DA - 2003-12-01 KW - Nanometer Confinement KW - Dielectric and thermal spectroscopy KW - Neutron scattering KW - Poly(methyl phenyl siloxane) PY - 2004 SN - 1-558-99728-8 DO - https://doi.org/10.1557/PROC-790-P9.3 SN - 0272-9172 N1 - Serientitel: Materials Research Society symposium proceedings – Series title: Materials Research Society symposium proceedings IS - 790 SP - P9.3.1 EP - P9.3.6 PB - Materials Research Society CY - Warrendale, Pa. AN - OPUS4-3520 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. A1 - Frick, B. A1 - Zorn, R. T1 - Glass transition of polymers confined to nanoporous glasses N2 - The glassy dynamics of poly(propylene glycol) (PPG) and poly(methyl phenyl siloxane) (PMPS) confined to nanoporous glasses (pore sizes 2.5–20 nm) investigated by dielectric spectroscopy, temperature modulated DSC and neutron scattering is compared. For both systems the relaxation rates estimated from dielectric spectroscopy and temperature modulated DSC agree quantitatively indicating that both experiments sense the glass transition. For PPG the glassy dynamics in nanopores is determined by a counterbalance of an adsorption and a confinement effect where the temperature dependence of the relaxation times obeys the Vogel/Fulcher/Tammann (VFT-) equation. The former effect results from an interaction of the confined macromolecules with the internal surfaces which in general slows down the molecular dynamics. A confinement effect leads to an acceleration of the segmental dynamics compared to the bulk state and points to an inherent length scale on which the glassy dynamics takes place. The step of the specific heat capacity Deltacp at the glass transition vanishes at a finite length scale of 1.8 nm. This result supports further the conception that a characteristic length scale is relevant for glassy dynamics. For PMPS down to a pore size of 7.5 nm the temperature dependence of the relaxation times follows the VFT-dependence and a confinement effect is observed like for PPG. At a pore size of 5 nm this changes to an Arrhenius-like behavior with a low activation energy. At the same pore size Deltacp vanishes for PMPS. This points to a dramatic change in the character of molecular motions responsible for glassy dynamics and supports further the relevance of a characteristic length scale on which it takes place. Quasielastic neutron scattering experiments on PMPS reveal that the microscopic dynamics characterized by the mean square displacement depends on confinement above the glass transition. The diffusive character of the relevant molecular motions seems to disappear at a length scale of about 1.6 nm. KW - Glass transition KW - Polymers KW - Nanoporous glasses KW - Glassy dynamics KW - Poly(propylene glycol) KW - Poly(methyl phenyl siloxane) PY - 2004 DO - https://doi.org/10.1007/s00396-004-1106-3 SN - 0303-402X SN - 1435-1536 VL - 282 SP - 882 EP - 891 PB - Springer CY - Berlin AN - OPUS4-3630 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Frick, B. A1 - Alba-Simionesco, C. A1 - Anastasiadis, S. H. A1 - Chrissopulou, K. A1 - Dalnoki-Veress, K. A1 - Dosseh, G. A1 - Forest, J. A1 - Hartmann, L. A1 - LeQuellec, C. A1 - Moreno, A. A1 - Schönhals, Andreas A1 - Zorn, R. T1 - Inelastic neutron scattering studies on glass-forming systems in coninement T2 - Fall Meeting Material Research Society of America CY - Boston, MA, USA DA - 2003-12-01 PY - 2003 AN - OPUS4-4194 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frick, B. A1 - Alba-Simionesco, C. A1 - Dosseh, G. A1 - Le Quellec, C. A1 - Moreno, A. J. A1 - Colmenero, J. A1 - Schönhals, Andreas A1 - Zorn, R. A1 - Chrissopoulou, K. A1 - Anastasiadis, S. H. A1 - Dalnoki-Veress, K. T1 - Inelastic neutron scattering for investigating the dynamics of confined glass-forming liquids N2 - Inelastic neutron scattering was employed over recent years to investigate the influence of spatial confinement on the dynamics of glass-forming systems. We review the common phenomena observed by neutron scattering in such different confining hosts like porous glasses, molecular sieves, clays or free standing polymer films, which impose a spatial limitation to the motion of small organic molecules, oligomers or polymers. Near the glass transition temperature the mean squared displacements of the confined molecules show clear deviations from the bulk behavior. The observed increase or decrease of the mean squared displacements confirms the high relevance of the interface interaction near walls of confining media without excluding additional real confinement effects. We show a new comparison of the mean squared displacement for PDMS and PMPS in bulk and in different type of restricting geometries, which evidence a weak influence of the restricting geometry on the local methyl group motion, but a strong influence on the glass transition dynamics, if wall interactions are taken into account. Strong wall interaction is also supported by the intermediate scattering function, measured either by combining neutron backscattering and time-of-flight experiments to cover 3 decades in time from ns to ps or by neutron spin echo, which reveal above Tg an increasing elastic fraction with decreasing pore size and a slowing down of the dynamics. Furthermore we show that a reduction of modes below the Boson peak frequency is a more general feature of confined glass-forming systems. PY - 2005 DO - https://doi.org/10.1016/j.jnoncrysol.2005.03.061 SN - 0022-3093 VL - 351 IS - 33-36 SP - 2657 EP - 2667 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-10831 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, Ch. A1 - Frick, b. A1 - Zorn, R. T1 - Polymers in nanoconfinement: What can be learned from relaxation and scattering experiments? N2 - Dielectric spectroscopy in combination with temperature modulated differential scanning calorimetry and quasielastic/inelastic neutron scattering are employed to investigate the molecular (glassy) dynamics of poly(dimethyl siloxane) (PDMS) and poly(methyl phenyl siloxane) (PMPS) confined to random nanoporous glasses with nominal pore sizes between 2.5 nm and 20 nm. Inside the pores PDMS and PMPS have faster molecular dynamics than in the bulk state. Down to a pore size of 7.5 nm the temperature dependence of the relaxation times (or rates) obeys the Vogel/Fulcher/Tammann (VFT) equation where the data obtained from dielectric and thermal spectroscopy agree quantitatively. At a pore size of 5 nm this VFT-like temperature dependence changes to an Arrhenius behavior. At the same confining length scale the increment of the specific heat capacity at Tg normalized to the weight of the confined polymer vanishes. The results indicate that a minimal length scale seems to be relevant for glassy dynamics in both polymers although the estimated length scale of about 5 nm seems to a bit too large in comparison to other experimental results and theoretical approaches. Neutron scattering is employed to investigate methyl group reorientation and the fast segmental dynamics of both polymers in confinement. Although the methyl group rotation is a localized process these experiments show that a part of the methyl groups is immobilized by the confinement whereas the effects for PDMS are much more pronounced than for PMPS. With regard to the segmental dynamics, neutron scattering reveals a big difference in the behavior of both polymers. Whereas the data obtained for PMPS are in accord with a boundary layer formed at the surfaces of the nanopores, for PDMS a considerable amount of elastic scattering is observed. To explain this result it is assumed that some structure formation of PDMS takes place in the nanopores, although the thermal data show no crystallization or melting effects. KW - Glass transition KW - Dielectric loss and relaxation KW - Macromolecular and polymer solutions KW - Polymer melts KW - Swelling PY - 2005 DO - https://doi.org/10.1016/j.jnoncrysol.2005.03.062 SN - 0022-3093 VL - 351 IS - 33-36 SP - 2668 EP - 2677 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-10856 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zorn, R. A1 - Frick, B. A1 - Hartmann, L. A1 - Kremer, F. A1 - Schönhals, Andreas A1 - Richter, D. T1 - Dynamics of confined glass-forming systems observed by neutron scattering N2 - In this article, results on the microscopic dynamics of a low-molecular glass former and a polymer confined in nanoporous silica obtained by inelastic neutron scattering are presented. By combining time-of-flight spectroscopy and backscattering spectroscopy we are able to cover a large dynamical range, from the low-frequency vibrations to the relaxation. The most prominent effect was observed on the “boson peak” in the vibrational spectrum. A strong reduction of the modes at lowest frequencies could be observed in both cases. The main effect on the relaxation is a broadening for the salol system. For the polymeric system a difference of the confinement influence on the methyl-group rotation and the relaxation can be detected from a first qualitative interpretation of the data. T2 - 3rd European Conference on Neutron Scattering (ECNS-3) CY - Montpellier, France DA - 2003-09-03 KW - Glass transition KW - Confinement PY - 2004 DO - https://doi.org/10.1016/j.physb.2004.03.303 SN - 0921-4526 SN - 1873-2135 VL - 350 IS - 1-3 SP - e1115 EP - e1118 PB - North-Holland Physics Publ. CY - Amsterdam AN - OPUS4-4589 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Schick, C. A1 - Huth, H. A1 - Frick, B. A1 - Mayorova, M. A1 - Zorn, R. T1 - Molecular dynamics in glass-forming poly(phenyl methyl siloxane) as investigated by broadband thermal, dielectric and neutron spectroscopy KW - Neutron diffraction/scattering KW - Dielectric properties KW - Relaxation KW - Electric modulus KW - Glass transition PY - 2007 SN - 0022-3093 VL - 353 IS - 41-43 SP - 3853 EP - 3861 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-15898 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zorn, R. A1 - Mayorova, M. A1 - Richter, D. A1 - Schönhals, Andreas A1 - Hartmann, L. A1 - Kremer, F. A1 - Frick, B. T1 - Effect of Nanoscopic Confinement on the Microscopic Dynamics of Glass-Forming Liquids and Polymers Studied by Inelastic Neutron Scattering N2 - In this article we present inelastic neutron scattering (INS) experiments on different systems of confined glass-formers. The aim of these experiments is to study the influence of spatial restriction on the microscopic dynamics related to the glass transition. Such results could be helpful for the detection of a currently speculated cooperativity length of the glass transition. The glass-forming component is either a molecular liquid or a polymer. The confining matrices are `hard' (silica glass, silicon) or `soft' (microemulsion droplets). For some experiments the confining structure could be spatially oriented. Except for the soft confinement the naïvely expected acceleration effect could only be found at low temperatures where INS experiments are difficult because of the long relaxation times. A clear effect of confinement could be observed for the glass-typical low energy vibrations (boson peak). This effect seems to be completely different for soft and hard confinement. Surprisingly, the experiments on oriented nanopores did not show any signs of an anisotropy of the dynamics. KW - Alpha relaxation KW - Boson peak KW - Confinement KW - Cooperativity length KW - Glass transition PY - 2008 SN - 978-0-7354-0501-1 DO - https://doi.org/10.1063/1.2897907 SN - 0094-243X SN - 1551-7616 SP - 79 EP - 84 PB - American Institute of Physics CY - Melville, NY, USA AN - OPUS4-17454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -