TY - JOUR A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Frunza, Stefan A1 - Bentrup, U. A1 - Fricke, R. A1 - Pitsch, I. A1 - Kosslick, H. T1 - Confinement of nematic liquid crystals in SBA mesoporous materials N2 - This work presents some results obtained by confining octylcyanobiphenyl (8CB) to the pores of two SBA-15 type host materials: a silica SBA-15 (pores of 10.2 nm) and an aluminum containing AlSBA-15 (pores of 7.5 nm). The LC molecules were loaded inside the pores from a solution in acetone, in a percentage higher than 70% from the maximum possible loading. It was observed that the 8CB molecules confined to molecular sieves may preserve the phase transitions characteristic for the bulk LC provided that the confining pores are sufficiently large, as offered by SBA materials. However, present guest-host interactions play an important role in these phase transitions. Such a behavior is at variance with the 8CB confined to Controlled Porous Glass with the same pore dimensions, for which the bulk-like phase transitions can be always observed. T2 - 2nd International FEZA conference CY - Taormina, Italy DA - 2002-09-01 PY - 2002 DO - https://doi.org/10.1016/S0167-2991(02)80296-8 SN - 0167-2991 VL - 142 IS - 2 SP - 1323 EP - 1329 PB - Elsevier CY - Amsterdam AN - OPUS4-2263 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Pitsch, I. A1 - Frunza, Stefan T1 - Molecular dynamics of 4n-octylcyanobiphenyl confined to nanoporous molecular sieves of SBA-type T2 - International Conference of Dielectric Spectroscopy CY - Leipzig, Germany DA - 2002-09-01 PY - 2002 SP - 1(?) AN - OPUS4-2264 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Frunza, Stefan A1 - Kosslick, H. T1 - Unusual relaxation behavior of water inside the sodalite cages of faujasite-type molecular sieves T2 - International Conference of Dielectric Spectroscopy CY - Leipzig, Germany DA - 2002-09-01 PY - 2002 SP - 1(?) AN - OPUS4-2265 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Stefan A1 - Frunza, Ligia T1 - Dinamica compozitelor aerosil - 8CB prin spectroscopie dielectrica; On the dynamics of aerosil - 8CB composites by dielectric spectroscopy T2 - Romanian Annual Conference 2002 CY - Târgu Mure¸s, Romania DA - 2002-09-01 PY - 2002 SP - 1(?) AN - OPUS4-2266 LA - ron AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Stefan A1 - Kosslick, H. A1 - Frunza, Ligia A1 - Enache, I. A1 - Beica, T. T1 - Studiul stratului de suprafata pe compozite aerosil - 8CB prin analiza termica / Study of surface layer in 8CB-aerosil composites by TG/DTA/TG measurements T2 - Annual Session of Romanian Research Program CERES CY - Bucharest, Romania DA - 2002-11-28 PY - 2002 AN - OPUS4-2267 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Pitsch, I. A1 - Fricke, R. A1 - Bentrup, U. A1 - Frunza, Stefan T1 - Nanoporous materials as hosts for liquid crystals T2 - DFG-Workshop on Key Program "Nanoporous Crystals" CY - Berlin, Germany DA - 2002-10-21 PY - 2002 SP - 1(?) AN - OPUS4-2268 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Frunza, S. A1 - Frunza, L. A1 - Goering, Harald T1 - On the dynamics of the surface layer in octylcynobiphenyl-aerosil nanocomposites T2 - Frühjahrstagung des Arbeitskreises Festkörperphysik bei der DPG CY - Regensburg, Germany DA - 2002-03-11 PY - 2002 SN - 0420-0195 SN - 0372-5448 SN - 0343-9216 IS - CPP 15.11 SP - 438 CY - Bad Honnef AN - OPUS4-2269 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Bentrup, U. A1 - Pitsch, I. A1 - Fricke, R. A1 - Frunza, Stefan ED - Barnes, A. J. T1 - First spectroscopic characterization of the surface layer in composites containing liquid crystals confined to nanopores T2 - 26th European Congress on Molecular Spectroscopy (EUCMOS) CY - Villeneuve-d'Ascq, France DA - 2002-09-01 KW - Liquid crystals KW - Confinement KW - Surface layer KW - Infrared spectroscopy KW - Band shape analysis PY - 2002 SN - 0022-2860 VL - 651-653 SP - 1(?) EP - 14(?) PB - Elsevier CY - Amsterdam AN - OPUS4-2270 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 - 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 - JOUR A1 - Turky, Gamal A1 - Schönhals, Andreas T1 - Influence of azobenzene concentration on the dielectric behavior of amorphous comb-like copolymers with photochromic side groups N2 - Dielectric spectroscopy in the frequency range from 10-2 to 106 Hz and in the temperature range from 190 to 440 K is employed to study the effect of azobenzene concentration on the dielectric relaxation processes of an amorphous comb-like copolymethacrylate. Four concentrations (x=29, 45.5, 54, and 74.5 mol%) of photochromic group 4-amino-azobenzene were investigated, where as comonomer a methacrylate unit having a derivative of benzanilide in the side group is used. Two prominent processes, the ?-relaxation at low temperatures which is related to rotational fluctuations of the mesogenic unit around its long axes and the dynamic glass transition (?-relaxation, segmental dynamics) at higher temperatures are observed for all azobenzene concentrations. In addition in between the ?- and the ?-relaxation a ??-process is observed for the polymers with the two lowest azobenzene concentrations, which seems to be related to the azobenzene unit. The dependence of the dielectric strength and the relaxation rate of the relaxation processes on the azobenzene concentration is discussed and interpreted in a simple phenomenological model, where also data obtained by semi empirical quantum chemical calculations are used. KW - Azobenzene KW - comb-like copolymer KW - Dielectric relaxation KW - Mesogenic unit PY - 2004 DO - https://doi.org/10.1016/j.polymer.2003.10.063 SN - 0032-3861 SN - 1873-2291 VL - 45 IS - 1 SP - 255 EP - 262 PB - Springer CY - Berlin AN - OPUS4-2867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - The behavior of polymers confined to nanoporous glasses investigated by dielectric, thermal and neutron spectroscopy T2 - Vortrag an der Universität Toulouse "Paul Sabatier" CY - Toulouse, France DA - 2004-07-21 PY - 2004 AN - OPUS4-3900 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dynamics of surface layer in cyanobiphenyl-aerosil nanocompositeswith a high silica density T2 - 3th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Delft, Netherlands DA - 2004-08-23 PY - 2004 AN - OPUS4-3902 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Nanoconfinements - What can we learn from relaxation and scattering experiments? T2 - 3th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Delft, Netherlands DA - 2004-08-23 PY - 2004 AN - OPUS4-3904 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Random Nanoporous Glasses: Molecular dynamics and Structure T2 - Fall Meeting Material Research Society of America CY - Boston, MA, USA DA - 2003-12-01 PY - 2003 AN - OPUS4-4061 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics and Structure of Polymers in Confining Space Revealed by Relaxation and Scattering Techniques T2 - International Workshop on Dynamics in Confinement CY - Grenoble, France DA - 2003-01-23 PY - 2003 AN - OPUS4-4108 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Broadband Dielectric Spetroskopy and its Application to Dynamic Glass Transition: From the Bulk to the Confined State T2 - International Discussion Seminar on Inelastic x-Ray Scattering (eingeladener Vortrag) CY - Grenoble, France DA - 2003-02-10 PY - 2003 AN - OPUS4-4109 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Broadband Dielectric Spetroskopy and its Application to Dynamic Glass Transition T2 - Frühjahrsschule "Festkörperphysik" der Universität Karlsruhe (eingeladene Vortrag) CY - Karlsruhe, Germany DA - 2003-02-17 PY - 2003 AN - OPUS4-4110 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polar Molecules in Nanoconfinements T2 - Vortrag Universität Lyon CY - Lyon, France DA - 2003-03-31 PY - 2003 AN - OPUS4-4111 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymere in Nano-Confinements: Vergleich von Relaxationsexperimenten und (Neutronen) streuung T2 - Kolloquium der Abteilung VI CY - Berlin, Germany DA - 2003-06-05 PY - 2003 AN - OPUS4-4113 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Inverse Nanocomposites: Structure and Dynamics of Polymers Confined to Nanopores T2 - 7th International Symposium Polymers for Advanced Technologies CY - Fort Lauderdale, FL, USA DA - 2003-09-21 PY - 2003 AN - OPUS4-4191 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers confined to nanoporous glasses: What can we leam from relaxation and scattering experiments? T2 - Softmatter Seminar des Forschungszentrums Jülich CY - Jülich, Germany DA - 2003-11-13 PY - 2003 AN - OPUS4-4192 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Random Nanoporous glasses: Molecular Dynamics and Structure T2 - Fall meeting Material Researsh Society of America CY - Boston, MA, USA DA - 2003-12-01 PY - 2003 AN - OPUS4-4193 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymere in nanoporösen Gläsern: Was können wir von Relaxations- und Streuexperimenten lernen? T2 - Workshop Glasübergang CY - Berlin, Germany DA - 2003-12-14 PY - 2003 AN - OPUS4-4196 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Rotational fluctuations of water inside nanopores/nanocavities of molecular sieves T2 - Workshop Confit 2006 CY - Grenoble, France DA - 2006-03-23 PY - 2006 AN - OPUS4-12015 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers confined to nanoporous glasses investigated by quasielastic and inelastic neutron scattering T2 - Workshop Confit 2006 CY - Grenoble, France DA - 2006-03-23 PY - 2006 AN - OPUS4-12000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular fluctuations of 4-n-octyl-4'cyanobiphenyl confined to nanoporous SBA-type molecular sieves with different filling degrees T2 - Workshop Confit 2006 CY - Grenoble, France DA - 2006-03-23 PY - 2006 AN - OPUS4-12005 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Neutron spectroscopy on polymers confined to nanoporous glasses T2 - Frühjahrstagung der Deutschen Physikalischen Gesellschaft CY - Dresden, Germany DA - 2006-03-21 PY - 2006 AN - OPUS4-12032 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Frunza, Stefan A1 - Schönhals, Andreas T1 - Molecular dynamics of 4-n-octyl-4'-cyanobiphenyl in partially filled nanoporous SBA-type molecular sieves N2 - The molecular dynamics of 4-n-octyl-4'-cyanobiphenyl (8CB) confined to the nanopores of new SBA-type molecular sieves was investigated in a wide temperature range using broadband dielectric spectroscopy (10-2–109 Hz). One molecular sieve has a hexagonal structure of the pores while the other is a cellular nanoporous material. To explore the extent of surface interaction effects a high and a low filling degree were considered. For the molecular sieves with a high filling degree two relaxation regions were observed: a bulk-like relaxation process related to molecules, which behave as mesophase, located in the centre of the pores. The second relaxation process has a much lower relaxation rate than the former and is assigned to molecules located in a surface layer. The temperature dependence of its relaxation rates follows the Vogel–Fulcher–Tammann law, characteristic for glassy dynamics. For samples with a low filling degree only one relaxation process due to the surface layer was observed. Moreover, especially at the temperatures lower than the melting point of bulk 8CB, its relaxation rate is situated between the characteristic frequencies of the two relaxation processes observed for the pores with a high filling degree. This behaviour gives a measure of the extension of the influence of the wall on the neighbouring 8CB molecules. In addition, the differences revealed by the molecule dynamics inside the two types of nanoporous materials are related to both surface interactions and geometrical constraints. KW - Confined liquid crystals KW - Molecular sieves KW - Dielectric measurements KW - Relaxation processes KW - Glassy dynamics PY - 2006 DO - https://doi.org/10.1016/j.micromeso.2005.10.025 SN - 1387-1811 SN - 1873-3093 VL - 90 IS - 1-3 SP - 259 EP - 270 PB - Elsevier CY - Amsterdam AN - OPUS4-12118 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. T1 - Poly(methyl phenyl siloxane) in Random Nanoporous Glasses - Comparison of coated and uncoated confining surfaces T2 - Poly(methyl phenyl siloxane) in Random Nanoporous Glasses: Comparison of coated and uncoated confining surfaces CY - Boston, MA, USA DA - 2006-11-28 PY - 2006 VL - 899E SP - 0899-N09-05.1-0899-N09-05.6 CY - Boston AN - OPUS4-12214 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Structure property relationships of different polymer based nanocomposites as investigated by dieletric spectroscopy and gas transport measurements T2 - 2nd International Symposium on Nanostructured and Functional Polymer-based Materials and Nanocomposites (NANOFUN-POLY) CY - Lyon, France DA - 2006-05-29 PY - 2006 AN - OPUS4-12393 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymer based nanocomposites as investigated by dielectric spectroscopy, gas transport measurements and related techniques T2 - NoE Nanofun Polymer, 6. FP der EU CY - Poznan, Poland DA - 2006-09-01 PY - 2006 AN - OPUS4-12625 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers confined to Nanoporous Glasses T2 - Vortrag am National Research Center, Kairo CY - Cairo, Egypt DA - 2005-10-16 PY - 2005 AN - OPUS4-11669 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Random Nanoporous Glasses Investigated by Dielectric, Thermal and Neutron Spectroscopy T2 - Herbst Meeting der Amerikanischen Gesellschaft für Materialforschung, 01.12. CY - Boston, MA, USA DA - 2005-11-27 PY - 2005 AN - OPUS4-11708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecules in nanometre confinement investigated by dieletric spectroscopy and related techniques T2 - 4. Conference of the International Dieletric Society CY - Poznan, Poland DA - 2006-09-03 PY - 2006 AN - OPUS4-13042 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schick, C. A1 - Sukhorukov, D. A1 - Schönhals, Andreas T1 - Comparison of the Molecular Dynamics of a Liquid Crystalline Side Group Polymer Revealed from Temperature Modulated DSC and Dielectric Experiments in the Glass Transition Region N2 - Temperature modulated DSC (TMDSC) in the frequency range from 10-3 Hz to 3.4 10-2 Hz and dielectric spectroscopy in the frequency range from 10-2 Hz to 106 Hz is employed to analyze the temperature dependence of the relaxation rates of the - and of the -relaxation of a liquid crystalline polymethacrylate having a derivative of (p-alkoxy-phenyl)-benzoate as mesogenic unit in the side group. Especially the molecular assignment of the -relaxation was discussed controversial in the literature up to now. By applying a temperature derivative method it was found that the temperature dependencies of the relaxation rates of the dielectric -relaxation and of the dynamic glass transition measured by TMDSC can be described by Vogel/Fulcher/Tammann laws with the same Vogel temperature. Therefore it is argued that the dielectric -relaxation of liquid crystalline polymers is rather due to the dynamic glass transition related to the segmental dynamics of the backbone than to the transverse dipole component of the mesogenic unit. PY - 2001 DO - https://doi.org/10.1002/1521-3935(20010501)202:8<1398::AID-MACP1398>3.0.CO;2-C SN - 1022-1352 SN - 1521-3935 VL - 202 IS - 8 SP - 1398 EP - 1404 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-13693 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers confined to nanoporous glasses investigated by quasielastic and inelastic neutron scattering T2 - Soft Matter User Meeting CY - Grenoble, France DA - 2006-11-22 PY - 2006 AN - OPUS4-13881 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in nanoconfinements investigated by various spectroscopic methods T2 - Department of Physics and Astronomy, Universität Leuven CY - Leuven, Belgium DA - 2006-11-30 PY - 2006 AN - OPUS4-14203 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics of polar molecules in nanometre confinement T2 - Vortrag an der Universität Lissabon, Fakultät für Chemie CY - Lisbon, Portugal DA - 2007-01-17 PY - 2007 AN - OPUS4-14503 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Neutron Spectroscopy on nano-confined polymers in comparison with dielectric and thermal results T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft, AK Chemische Physik/Polymerphysik CY - Regensburg, Germany DA - 2007-03-26 PY - 2007 AN - OPUS4-14566 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 - Mayorova, M. T1 - Segmental dynamics of poly(methyl phenyl siloxane) confined to nanoporous glasses N2 - The effect of a nanometer confinement on the molecular dynamics of poly(methyl phenyl siloxane) (PMPS) was studied by dielectric spectroscopy (DS), temperature modulated DSC (TMDSC) and neutron scattering (NS). Nanoporous glasses with pore sizes of 2.5–20 nm have been used. DS 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. For high temperatures the temperature dependence of the relaxation rates for confined PMPS crosses that of the bulk state. Besides finite states effects also the thermodynamic state of nano-confined PMPS is different from that of the bulk. At a pore size of 5 nm the temperature dependence of the relaxation times changes from a Vogel/Fulcher/Tammann like to an Arrhenius behavior where the activation energy depends on pore size. This is in agreement with the results obtained by NS. The increment of the specific heat capacity at the glass transition depends strongly on pore size and vanishes at a finite length scale between 3 and 5 nm which can be regarded as minimal length scale for glass transition to appear in PMPS. PY - 2007 SN - 1951-6355 SN - 1951-6401 VL - 141 IS - 1 SP - 255 EP - 259 PB - Springer CY - Berlin AN - OPUS4-14602 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dielectric and neutron spectroscopy on nano-confined liquid crystals T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft, AK Chemische Physik/Polymerphysik CY - Regensburg, Germany DA - 2007-03-26 PY - 2007 AN - OPUS4-14590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular dynamics in glass-forming liquid crystal as studied by broadband dielectric and thermal spectroscopy T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft, AK Chemische Physik/Polymerphysik CY - Regensburg, Germany DA - 2007-03-26 PY - 2007 AN - OPUS4-14592 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hao, Ning A1 - Böhning, Martin A1 - Goering, Harald A1 - Schönhals, Andreas T1 - Nanocomposites of Polyhedral Oligomeric Phenethylsilsesquioxanes and Poly(bisphenol A carbonate) as Investigated by Dielectric Spectroscopy N2 - Nanocomposites were prepared by solution blending of polyhedral oligomeric silsesquioxane with phenethyl substituents (PhenethylPOSS) into poly(bisphenol A carbonate) (PBAC). The nanocomposites were investigated by dielectric spectroscopy, differential scanning calorimetry (DSC) and density measurements. PhenethylPOSS shows one relaxation process, the α-relaxation, confirmed by DSC investigations. PBAC shows a β-relaxation at lower and an α-relaxation at higher temperatures. With increasing PhenethylPOSS content the α-relaxation of the composites shifts to lower temperatures. Thus, incorporation of PhenethylPOSS leads to a plasticization of PBAC due to a decrease of the packing density which is rationalized by density measurements. For higher concentrations of PhenethylPOSS (>10 wt %) the α-relaxation of the polycarbonate matrix splits into two peaks. Moreover, close to the α-relaxation of PhenethylPOSS a third process is observed. These results indicate a phase separation into a PBAC matrix with a few percents of molecularly solved POSS and POSS-rich domains. These POSS-rich domains are surrounded by an interfacial layer of PBAC having a higher concentration of POSS than the matrix. A phase diagram is deduced providing a miscibility criterion. For the phase separated nanocomposites an interfacial polarization phenomena is observed. Using a simplified model the time constant of this process is correlated with the size of the PhenethylPOSS-rich domains and theire increasing size with the increase of the concentration of POSS. KW - Polyhedral oligomeric silsesquioxane (POSS) KW - Polymer-based nanocomposites KW - Broadband dielectric spectroscopy KW - Interfacial polarisation PY - 2007 SN - 0024-9297 SN - 1520-5835 VL - 40 IS - 8 SP - 2955 EP - 2964 PB - American Chemical Society CY - Washington, DC AN - OPUS4-14768 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brás, A. R. A1 - Dionísio, M. A1 - Huth, H. A1 - Schick, C. A1 - Schönhals, Andreas T1 - Origin of glassy dynamics in a liquid crystal studied by broadband dielectric and specific heat spectroscopy N2 - A combination of broadband dielectric (10-2 Hz–109 Hz) and specific heat (10-3 Hz–2×103 Hz) spectroscopy is employed to study the molecular dynamics of the glass-forming nematic liquid crystal E7 in a wide temperature range. In the region of the nematic phase the dielectric spectra show two relaxation processes which are expected theoretically: The δ relaxation which corresponds to rotational fluctuations of the molecules around its short axis and the tumbling mode at higher frequencies than the former one. For both processes the temperature dependence of the relaxation rates follows the Vogel-Fulcher-Tammann formula which is characteristic for glassy dynamics. By applying a detailed data analysis, it is shown that close to the glass transition the tumbling mode has a much steeper temperature dependence than the δ process. The former has a Vogel temperature which is by 30 K higher than that of the δ relaxation. Specific heat spectroscopy gives one relaxation process in its temperature and frequency dependence which has to be assigned to the α relaxation (dynamic glass transition). The unique and detailed comparison of the temperature dependence of the dielectric and the thermal relaxation rates delivers unambiguously that the dielectric tumbling mode has to be related to the dynamic glass transition. PY - 2007 DO - https://doi.org/10.1103/PhysRevE.75.061708 SN - 1539-3755 SN - 1063-651X VL - 75 IS - 6 SP - 061708-1-061708-8 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-15041 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Structure property relationships of polymeric nanocomposites based on polyhedral oligomeric silsesquioxanes T2 - Meeting American Chemical Society CY - Boston, MA, USA DA - 2007-07-19 PY - 2007 AN - OPUS4-15457 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hao, Ning A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Gas Transport Properties of Polymeric Nanocomposites Based on Polyhedral Oligomeric Silsesquioxanes PY - 2007 SN - 0743-0515 VL - 97 SP - 444 EP - 445 PB - Division of Polymeric Materials Science and Engineering, American Chemical Society CY - Washington, DC AN - OPUS4-15846 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 - Schönhals, Andreas T1 - Molecular mobility poly(phenyl methyl siloxane) invesstigated by thermal, dielectric and neutron spectroscopy T2 - Meeting of the American Chemical Society, PMSE CY - Boston, MA, USA DA - 2007-08-19 PY - 2007 AN - OPUS4-15463 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, L. A1 - Schönhals, Andreas A1 - Frunza, S. A1 - Parvulescu, V.I. A1 - Cojocaru, B. A1 - Carriazo, D. A1 - Martín, C. A1 - Rives, V. T1 - Rotational Fluctuations of Water Confined to Layered Oxide Materials - Nonmonotonous Temperature Dependence of Relaxation Times N2 - The rotational molecular dynamics of water confined to layered oxide materials with brucite structure was studied by dielectric spectroscopy in the frequency range from 10-2 to 107 Hz and in a broad temperature interval. The layered double hydroxide samples show one relaxation process, which was assigned to fluctuations of water molecules forming a layer, strongly adsorbed to the oxide surface. The temperature dependence of the relaxation rates has an unusual saddlelike shape characterized by a maximum. The model of Ryabov et al. (J. Phys. Chem. B 2001, 105, 1845) recently applied to describe the dynamics of water molecules in porous glasses is employed also for the layered materials. This model assumes two competing effects: rotational fluctuations of water molecules that take place simultaneously with defect formation, allowing the creation of free volume necessary for reorientation. The activation energy of rotational fluctuations, the energy of defect formation, a pre-exponential factor, and the defect concentration are obtained as main parameters from a fit of this model to the data. The values of these parameters were compared with those found for water confined to nanoporous molecular sieves, porous glasses, or bulk ice. Several correlations were discussed in detail, such as the lower the value of the energy of defect formation, the higher the number of defects. The pre-exponential factor increases with increasing activation energy, as an expression of the compensation law, and indicates the cooperative nature of the motional process. The involvement of the surface OH groups and of the oxygen atoms of the interlayer anions in the formation of hydrogen bonds was further discussed. For the birnessite sample, the relaxation processes are probably overlaid by a dominating conductivity contribution, which is analyzed in its frequency and temperature dependence. It is found that the conductivity of birnessite obeys the characteristics of semiconducting disordered materials. Especially the Barton/Nakajima/Namikawa relationship is fulfilled. Analyzing the temperature dependence of the direct current (dc) conductivity σ0 in detail gives some hint that σ0(T) has also an unusual saddlelike form. PY - 2007 DO - https://doi.org/10.1021/jp0717140 SN - 1089-5639 SN - 1520-5215 VL - 111 IS - 24 SP - 5166 EP - 5175 PB - Soc. CY - Washington, DC AN - OPUS4-15718 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 Mobility of Poly(phenyl methyl siloxane) Investigated by Thermal, Dielectric and Neutron Spectroscopy PY - 2007 SN - 0743-0515 VL - 97 SP - 948 EP - 949 PB - Division of Polymeric Materials Science and Engineering, American Chemical Society CY - Washington, DC AN - OPUS4-15736 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Schönhals, Andreas ED - Grellmann, W. ED - Seidler, S. T1 - Electrical and Dielectrical Properties KW - Polymer Testing PY - 2007 SN - 978-3-446-40900-2 IS - Kap. 6.3 SP - 335 EP - 374 PB - Carl Hanser Verlag CY - Munich AN - OPUS4-15763 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dielectric properties of nanocomposites based on polyethylene and layered double hydroxide T2 - Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Arbeitskreis Chemische Physik und Polymerphysik CY - Berlin, Germany DA - 2008-02-25 PY - 2008 AN - OPUS4-16700 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -