TY - CONF A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Schönhals, Andreas T1 - Unveiling the heterogeneous structure of miscible polymer blend confined in ultrathin films via nanosized relaxation spectroscopy N2 - Advances in functional coatings, batteries, innovative organic electronics, and hybrid materials depend strongly on polymeric materials confined in thin films or adsorbed at surfaces. Subsequently, understanding the materials behavior under confinement and the deviations, from the bulk, that might arise is necessary for optimized technological applications. In the nanometer vicinity, solid interfaces and free surfaces could alter for instance entanglements, glassy dynamics (α-relaxation), and the thermal glass transition temperature (Tg), compared to the bulk behavior. Consequently, this could change macroscopic quantities of thin films like adhesion, wettability, friction, reactivity, and biocompatibility, which are topical problems for hybrid materials. In fact, despite the intense investigations on thin homopolymers films, little is known about polymer blend thin films and how blending affect glass dynamics and glass transition, under confinement. This work discusses the glassy dynamics of thin films of Poly (vinyl methyl ether) (PVME) with special focus to the dynamics near the interfaces. Further, PVME is then blended with the well-studied polystyrene (PS) in two concentrations; 50:50 and 25:75 wt-%, which are miscible in bulk. The glass dynamics of thin films of both blend concentration are then investigated. Here, a combination of nanosized relaxation spectroscopies; broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS); employing AC nanochip calorimetry, was utilized to probe the glassy dynamics of the thin films, thickness: 7nm – 200 nm. It should be noted that both methods are sensitive to different probes; where SHS senses entropy fluctuations while BDS measures dipole fluctuations. For BDS measurements, a recently developed nano-structured electrode sample arrangement was employed; where ultra-thin films are spin-coated on an ultra-flat highly conductive silicon wafer, sandwiched between a wafer with nanostructured SiO2 nano-spacers with heights between 35 nm and 70 nm. Furthermore, these measurements are then combined with surface analytical techniques; ellipsometry and AFM, for controlled film thickness and topography. Probing of PVME thin films revealed the existence of an adsorbed layer with a restricted mobility at the polymer/substrate interface, which is independent from the bulk-like behavior and thickness independent. As for PVME/PS thin films, it was shown that the overall segmental dynamics of both blends are strongly affected by a fine counter-balance between a free surface layer at the polymer/air interface, which is PVME-rich layer, and an adsorbed layer at the polymer/substrate interface, which is PS-rich. This is the first example where confinement induced changes were observed by BDS for ultra-thin films. All results were analyzed in details and will be comprehensively discussed. T2 - Seminar at University of Pennsylvania CY - Philadelphia, USA DA - 21.03.2017 KW - Ultra-thin polymer films PY - 2017 AN - OPUS4-39621 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Schönhals, Andreas T1 - Unveiling the Dynamics of Self-Assembled Layers of Thin Films of PVME by Nanosized Relaxation Spectroscopy N2 - In thin polymer films, little is known about the dynamics of the adsorbed layers, despite their importance in innovative applications. Here, Broadband Dielectric Spectroscopy (BDS) was utilized to investigate the glassy dynamics of thin films of a low MW Poly (vinyl methyl ether) (PVME) (thicknesses: 7 – 160 nm). A recently developed nano-structured capacitor arrangement was employed; where a silicon wafer with nanostructured SiO2 nano-spacers, with heights of 35 nm and 70 nm, is placed on top of a thin film spin coated on an ultra-flat highly conductive silicon wafer. Further, PVME/SiO2 interactions was confirmed by contact angle measurements, hence an adsorbed layer is allowed to form. For films with thicknesses smaller than 50 nm, BDS measurements showed two relaxation processes. The first process coincided, in its position and temperature dependence, with the -relaxation of bulk PVME, thus it was assigned to the -relaxation of a bulk-like layer. The second process showed a different temperature dependence and was ascribed to the relaxation of polymer segments adsorbed at the substrate. Both processes showed no thickness dependence. The results will be discussed in detail. To our knowledge, this is the first study of the segmental dynamics of an adsorbed layer in thin films. T2 - Marchmetting American Physical Society CY - New Orleans, USA DA - 13.03.2017 KW - Ultra thin polymer films PY - 2017 AN - OPUS4-39592 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Schönhals, Andreas T1 - In-situ probing of the dynamics of irreversibly adsorbed layers in PVME thin films N2 - For many years now, the so-called three layer model (free-surface, bulk-like, and adsorbed layers) has been commonly used, along with other parameters, to explain the deviations seen in glass transition and glassy dynamics for polymers confined into thin films, compared to their bulk value. Nevertheless, due to the hard accessibility of the adsorbed layers in supported films, little is known about the nature of their dynamics and how they really influences the overall dynamics of the thin films. Here, the irreversibly self-assembled adsorbed layer of a low MW Poly (vinyl methyl ether) (PVME) is solvent-leached from a 200 nm film. The thickness and topography of this layer is checked with Atomic Force Microscopy (AFM), to insure no dewetting and low roughness. Further, the dynamics of the adsorbed layer is then in-situ probed with Broadband Dielectric Spectroscopy (BDS). A recently developed nano-structured capacitor arrangement was employed; where a silicon wafer with nanostructured SiO2 nano-spacers, with heights of 35 nm, is placed on top of a thin film spin coated on an ultra-flat highly conductive silicon wafer. All results will be discussed in detail and quantitatively compared to our recent work on the glassy dynamics of PVME thin films (50 nm- 7nm), where BDS measurements showed two thickness-independent relaxation processes. The first process was assigned to the -relaxation of a bulk-like layer. Whereas the second process showed a different temperature dependence and was ascribed to the relaxation of polymer segments adsorbed at the substrate. To our knowledge, this is the first in-situ study of the dynamics of an irreversibly adsorbed layer. T2 - 8th International Discussion Meeting Relaxation in Complex Systems CY - Wisla, Poland DA - 23.07.2017 KW - Thin films PY - 2017 AN - OPUS4-41190 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -