TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics of Polymers Confined to Nanoporous Glasses T2 - Frühjahrstagung der Amerikanischen Chemischen Gesellschaft CY - San Diego, CA, USA DA - 2005-03-13 PY - 2005 AN - OPUS4-7778 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schönhals, Andreas ED - Grellmann, W. ED - Seidler, S. T1 - Elektrische und dielektrische Eigenschaften KW - Elektrische Eigenschaften KW - Dielektrische Eigenschaften KW - Kunststoffe PY - 2005 SN - 3-446-22086-0 SP - 352 EP - 395 PB - Hanser CY - München AN - OPUS4-10530 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hakme, C. A1 - Stevenson, I. A1 - David, L. A1 - Boiteux, G. A1 - Seytre, G. A1 - Schönhals, Andreas T1 - Uniaxially stretched poly(ethylene naphthalene 2,6-dicarboxylate) films studied by broadband dielectric spectroscopy N2 - The thermal behaviors of amorphous PEN films uniaxially stretched above and below Tg have been characterized by Temperature Modulated DSC. When drawing is performed above Tg, the degree of crystallinity and the glass transition temperature Tg increase with increasing drawing ratio. PEN samples stretched below Tg are more crystalline than when stretched above Tg. Moreover the cold crystallization phenomenon disappears with drawing as a result of the mechanically induced crystallization. Broadband dielectric spectroscopy has also been used to study the influence of the orientation on the molecular mobility of PEN to gain insight into the microscopic origin of the relaxation processes in the transverse direction i.e. when the electric field is perpendicular to the stretching direction. Dielectric relaxation phenomena are thus discussed as a function of the microstructure (orientation, crystallinity). The α-relaxation dynamics associated with the glass transition are largely slowed down by the drawing process and the relaxation strength decreases. This can be related to a transformation of the amorphous phase into (i) crystalline, (ii) rigid amorphous fraction (RAF) and/or constrained amorphous phase with lower molecular mobility due to the crystallization induced by the orientation process. In contrast, the dynamics of the ß*-relaxation are apparently increased and the activation energy for the uniaxially stretched samples decreases compared to the unstretched isotropic amorphous state. If the ß*-relaxation is assigned to the presence of naphthalene aggregates, this leads to the conclusion that stretching is structurally altering the naphthalene aggregates (creation of defective aggregates that induces a higher molecular mobility) or orientation is selecting the faster motions active for ß*. The ß-relaxation which corresponds to more local motions implying reorientation of the ester groups seems to be broad and composed of two components as in the case of PET: the ß1- and ß2-relaxations. While the high frequency ß1-component relaxation strength is increasing significantly with the deformation below Tg, that of the ß2-process is more related to the presence of water. KW - Poly(ethylene 2,6-naphthalene-dicarboxylate) KW - Dielectric Relaxation Spectroscopy (DRS) KW - TMDSC PY - 2005 DO - https://doi.org/10.1016/j.jnoncrysol.2005.05.039 SN - 0022-3093 VL - 351 IS - 33-36 SP - 2742 EP - 2752 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-10855 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 - 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 - Hardy, L. A1 - Stevenson, I. A1 - Fritz, A. A1 - Boiteux, G. A1 - Seytre, G. A1 - Schönhals, Andreas T1 - Dielectric and dynamic mechanical relaxation behaviour of poly(ethylene 2,6-naphthalene dicarboxylate). II. Semicrystalline oriented films N2 - The dielectric and dynamic mechanical behaviour of bi-stretched non-treated and annealed semicrystalline poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) films are studied as a function of different morphologies obtained by thermal treatments at temperatures close to the melting temperature of a semicrystalline film. Differential scanning calorimetry (DSC) shows that the glass transition temperatures do not change significantly with the thermal treatment for bi-stretched films. However, the melting temperatures and the degree of crystallinity increase with the value of annealing temperature. Both dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA) display three relaxation processes. In order of decreasing temperature, can be observed: the ?-relaxation due to the glass transition, the ?*-process assigned to cooperative molecular motions of the naphthalene groups which aggregate and the ?-relaxation due to local fluctuations of the carbonyl groups. The ?-relaxation process shifts to higher temperatures for the 250 and 260 °C treated bi-stretched semicrystalline samples compared to the sample thermally treated at 240 °C according to DRS data but shifts to lower temperatures according to the DMA measurements for the three annealed samples. This discrepency results from the different sensitivity of each methods with regards to the release of orientation. At a fixed frequency the temperature associated to ?*-relaxation is lower for the non-treated bi-stretched semicrystalline samples than for the treated ones using DMA but no difference can be seen in DRS. The associated apparent activation energies are rather high which suggest cooperative motions. It is assumed that the orientation of the samples prevents coupling between the naphthalene groups due to the stretched chain configuration in the amorphous phase. The activation energy for the ?-process given by DRS is independent of the thermal treatment and the value agrees with those found for poly(ethylene terephthalate) (PET) and amorphous PEN. Evidence of the decrease of orientation in the sample with thermal treatment can be seen via the onset of mobility, both by DRS and DMA. Thus, the orientation induces a greater change of properties compared to the crystalline samples obtained from the thermal treatment of an amorphous sample. Finally, a three phase model is proposed since there is evidence of a rigid amorphous phase present in PEN biaxially stretched samples which was favoured by the dependence of dielectric relaxation strengths on the degree of crystallinity for the ?*- and ?-relaxation. KW - Dielectric relaxation spectroscopy KW - Dynamic mechanical analysis KW - Poly(ethylene 2,6-naphthalene dicarboxylate) PY - 2003 DO - https://doi.org/10.1016/S0032-3861(03)00332-X SN - 0032-3861 SN - 1873-2291 VL - 44 IS - 15 SP - 4311 EP - 4323 PB - Springer CY - Berlin AN - OPUS4-2604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Simon, G. P. A1 - Schönhals, Andreas ED - Simon, G. P. T1 - Dielectric Relaxation and Thermal Stimulated Currents PY - 2003 SN - 0-8412-3818-9 SP - 96 EP - 130 PB - American Chemical Society CY - Washington, DC AN - OPUS4-2615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Confinement of nematic liquid crystals in SBA mesoporous materials T2 - 2nd International Feza (Federation of the European Zeolite Associations) Conference CY - Taormina, Italy DA - 2002-09-01 PY - 2002 AN - OPUS4-3558 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 - Schönhals, Andreas T1 - Dielectric Investigations under Irradiation of Photochromic Copolymers with Azobenzene Moieties in the Side Group T2 - 7th International Symposium Polymers for Advanced Technologies CY - Fort Lauderdale, FL, USA DA - 2003-09-21 PY - 2003 AN - OPUS4-4666 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. T1 - Segmental Dynamics of Polymeric Liquids Confined to Nanoporous Glasses T2 - ACS 2002 Biennial Symposium "Polymeric Nanomaterials" CY - Rohnert Park, CA, USA DA - 2002-11-17 PY - 2002 AN - OPUS4-2055 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Turky, Gamal A1 - Schönhals, Andreas T1 - Influence of azobenzene concentration on the dielectric behavior of amorphous comb-like copolymers with photochromic azobenzene side groups T2 - 2nd International Conference on Broadband Dielectric Spectroscopy and Its Applications CY - Leipzig, Germany DA - 2002-09-02 PY - 2002 AN - OPUS4-2056 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular dynamics and structure of molecules in confining geometries - A comparison of relaxation and scattering techniques T2 - 2nd International Conference on Broadband Dielectric Spectroscopy and Its Applications CY - Leipzig, Germany DA - 2002-09-02 PY - 2002 AN - OPUS4-2039 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -