Structure and dynamics of nanoconfined glass-forming oligomers and diblock coplymers (BPCs) are investigated by a combination of infrared transition moment orientational analysis (IR-TMOA), positron annihilation lifetime spectroscopy (PALS), grazing incidence small angle X-ray scattering (GISAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and broadband dielectric spectroscopy (BDS). The oligomers probed are the van der Waals type, tris(2-ethyhexyl)phosphate (TEHP) and the self-associating molecules of 2-ethyl-1-hexanol (2E1H). Symmetric and asymmetric poly(styrene-b-1,4-isoprene) P(S-b-I) are studied for the case of BCPs. The samples are confined either in one-dimensional (1D) in form of thin films or in 2D (nanopores) geometrical constraints. The molecular order of TEHP in nanopores as studied by IR-TMOA shows that about 7% of the molecules are preferentially oriented perpendicular to the long axis of the pores due to their interaction with the pore walls. PALS results reveal that 2E1H confined in nanopores exhibit larger free volume with respect to the bulk. In thin films (1D), P(S-b-I) having volume fraction of isoprene blocks f(PI)= 0.55 exhibits randomly oriented lamellae and their thicknesses are directly proportional to the film thickness d(film). For f(PI) = 0.73, perpendicular cylinders with respect to the substrate are observed for d(film)>50 nm but they lie along the substrate plane when d(film) < 50 nm. In AAO pores (2D) with average pore diameter d(pore) of 150 nm, straight nanorods are formed which change to helical structures in 18 nm pores. Molecular dynamics of 2E1H and TEHP constrained in nanopores (2D), is influenced by the interplay between confinement and surface effects. Confinement effects show up as an increase in the structural relaxation rate with decreasing pore sizes at the vicinity of the glass transition temperature. This is attributed to the reduced packing density of the molecules in pores as quantified by PALS results for 2E1H. Whereas the orientation and morphologies of the domains in P(S-b-I) and the chain dynamics of isoprene chains are influenced by the finite--size and dimensionality of confinement, the segmental motion, related to the dynamic glass transition (DGT) of both styrene and isoprene blocks remains unaffected-in its relaxation time-within experimental accuracy. Effects of nanoscale confinement on the molecular dynamics therefore depend on a number of factors: the type of molecules (polymers, low molecular liquids), interfacial interactions and the dimensionality of the constraining geometries.

Structure and dynamics of nanoconfined glass-forming oligomers and diblock coplymers (BPCs) are investigated by a combination of infrared transition moment orientational analysis (IR-TMOA), positron annihilation lifetime spectroscopy (PALS), grazing incidence small angle X-ray scattering (GISAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and broadband dielectric spectroscopy (BDS). The oligomers probed are the van der Waals type, tris(2-ethyhexyl)phosphate (TEHP) and the self-associating molecules of 2-ethyl-1-hexanol (2E1H). Symmetric and asymmetric poly(styrene-b-1,4-isoprene) P(S-b-I) are studied for the case of BCPs. The samples are confined either in one-dimensional (1D) in form of thin films or in 2D (nanopores) geometrical constraints. The molecular order of TEHP in nanopores as studied by IR-TMOA shows that about 7% of the molecules are preferentially oriented perpendicular to the long axis of the pores due to their interaction with the pore walls. PALS results reveal that 2E1H confined in nanopores exhibit larger free volume with respect to the bulk. In thin films (1D), P(S-b-I) having volume fraction of isoprene blocks f(PI)= 0.55 exhibits randomly oriented lamellae and their thicknesses are directly proportional to the film thickness d(film). For f(PI) = 0.73, perpendicular cylinders with respect to the substrate are observed for d(film)>50 nm but they lie along the substrate plane when d(film) < 50 nm. In AAO pores (2D) with average pore diameter d(pore) of 150 nm, straight nanorods are formed which change to helical structures in 18 nm pores. Molecular dynamics of 2E1H and TEHP constrained in nanopores (2D), is influenced by the interplay between confinement and surface effects. Confinement effects show up as an increase in the structural relaxation rate with decreasing pore sizes at the vicinity of the glass transition temperature. This is attributed to the reduced packing density of the molecules in pores as quantified by PALS results for 2E1H. Whereas the orientation and morphologies of the domains in P(S-b-I) and the chain dynamics of isoprene chains are influenced by the finite--size and dimensionality of confinement, the segmental motion, related to the dynamic glass transition (DGT) of both styrene and isoprene blocks remains unaffected-in its relaxation time-within experimental accuracy. Effects of nanoscale confinement on the molecular dynamics therefore depend on a number of factors: the type of molecules (polymers, low molecular liquids), interfacial interactions and the dimensionality of the constraining geometries.

No description available.

No description available.

We characterize the impact of high-energy, 172 nm vacuum ultraviolet photons on the molecular weight and the glass transition temperature of poly(methyl methacrylate). We found that the molecular weight is reduced strongly on the surface of the exposed samples with a continuous transition towards the unexposed bulk material being located below the modified region. The glass transition temperature was found to be significantly lowered in the exposed region to well below 50°C compared to that of the 122°C of the bulk region. We could use this material contrast to selectively reflow the top surface of the exposed samples only. This allowed us to create ultra-smooth micro-optical structures by postprocessing without influencing the overall geometry that is required for the optical functionality.

Mit verschiedenen experimentellen Methoden werden die strukturabhängigen Eigenschaften amorpher Zr-Al-Ni-Cu- und Ta-Si-N- Multikomponentenschichten untersucht. Aus Messungen der mechanischen Spannungen in amorphen Zr-Al-Ni-Cu-Schichten werden mit hoher Empfindlichkeit relative Volumenänderungen bestimmt, die bei Schichtwachstum, Relaxation und Kristallisation auftreten. Das Meßverfahren ermöglicht Untersuchungen der Spannungsrelaxation und Viskosität in der Nähe des Glasübergangs. Irreversible Spannungsrelaxationen unterhalb von Tg können mit der "Freie Volumen-Theorie" gedeutet werden. Als Ursache für eine schnelle Abnahme von Druckspannungen im Bereich des Glasübergangs wird dagegen ein Fließprozeß vorgeschlagen. Unmittelbar während der Kristallisation werden nur geringe Spannungsänderungen festgestellt. Aus Messungen der isothermen Spannungsrelaxation werden Viskositäten der amorphen Schichten bestimmt. Aus den Spannungsmessungen ergeben sich neue Erkenntnisse über das Relaxations- und Kristallisationsverhalten von Multikomponentengläsern. Es werden grundlegende Fragestellungen zu Entmischungs- und Kristallisationsvorgängen in amorphen Ta-Si-N-Schichten untersucht, die auch für technologische Anwendungen der Schichten als Diffusionsbarrieren relevant sind. ASAXS-, TEM- und XRD- Messungen ergeben, daß in amorphen Ta40Si14N46-Schichten bei Temperaturen zwischen 1073 K und 1273 K komplexe Prozesse, wie eine Phasenseparation und eine nachfolgende Nanokristallisation ablaufen. Diese Prozesse führen zu einer Bildung von Strukturen mit charakteristischen Ausdehnungen und wirken sich auf die mechanischen Spannungen aus. Durch die vorliegenden Ergebnisse wird gezeigt, daß die Stabilität der Diffusionsbarrieren bereits unterhalb der Kristallisationstemperatur durch die Entmischung und Nanokristallisation begrenzt ist.

Broadband Dielectric Spectroscopy (BDS) in combination with a nanostructured electrode arrangement – which circumvents the conventional need to evaporate metal electrodes onto soft matter – is used to study the molecular dynamics of several glass forming materials confined in nanometric (> 5 nm) layers. Other complementary experimental tools employed in this work include spectroscopic vis-Ellipsometry (SE), AC-chip calorimetry (ACC), X-ray reflectrometry (XRR), Differential Scanning Calorimetry (DSC) and Atomic Force Microscopy (AFM). The latter is used to characterize the topography of the samples and to determine their thicknesses. Under the conditions of annealing samples (Tg + 50K) in high oil-free vacuum (10E-6 mbars) for at least 12 h and carrying out measurements in inert (dry nitrogen or argon) atmosphere, it is found for all studied thin layers that the structural relaxation, and hence the dynamic glass transition – in its mean relaxation times – remains within a margin ±3 K from the respective bulk behaviour. It is revealed, inter alia, that the one-dimensional confinement of thin films introduces restrictions on other (slower) molecular relaxation processes which manifest, depending on the specific system under investigation, as (i) an interruption of the end-to-end (normal mode) fluctuation of the chains, or (ii) a slowing down of the delta-relaxation when the system is cooled towards glass-formation. Furthermore, (iii) evidence is provided to show that the dimensionality of confinement plays a significant role in determining the resulting dynamics. A molecular understanding of these findings is given, and the discussion presented with respect to the on-going international debate about dynamics in confinement.

No description available.

No description available.

Broadband Dielectric Spectroscopy (BDS) in combination with a nanostructured electrode arrangement – which circumvents the conventional need to evaporate metal electrodes onto soft matter – is used to study the molecular dynamics of several glass forming materials confined in nanometric (> 5 nm) layers. Other complementary experimental tools employed in this work include spectroscopic vis-Ellipsometry (SE), AC-chip calorimetry (ACC), X-ray reflectrometry (XRR), Differential Scanning Calorimetry (DSC) and Atomic Force Microscopy (AFM). The latter is used to characterize the topography of the samples and to determine their thicknesses. Under the conditions of annealing samples (Tg + 50K) in high oil-free vacuum (10E-6 mbars) for at least 12 h and carrying out measurements in inert (dry nitrogen or argon) atmosphere, it is found for all studied thin layers that the structural relaxation, and hence the dynamic glass transition – in its mean relaxation times – remains within a margin ±3 K from the respective bulk behaviour. It is revealed, inter alia, that the one-dimensional confinement of thin films introduces restrictions on other (slower) molecular relaxation processes which manifest, depending on the specific system under investigation, as (i) an interruption of the end-to-end (normal mode) fluctuation of the chains, or (ii) a slowing down of the delta-relaxation when the system is cooled towards glass-formation. Furthermore, (iii) evidence is provided to show that the dimensionality of confinement plays a significant role in determining the resulting dynamics. A molecular understanding of these findings is given, and the discussion presented with respect to the on-going international debate about dynamics in confinement.:1. Introduction 2. The glass transition and chain dynamics 2.1 The phenomenology of the glass transition 2.2 Theories of the glass transition 2.2.1 Free volume theories 2.2.2 Cooperative concepts 2.2.3 Mode-coupling theory 2.3 Dynamics of polymer chains in melt 2.4 The dynamic glass transition in confinement 2.4.1 Experiments: state-of-the-art 2.4.2 Theoretical attempts at explaining dynamics in confinement 3. Sample preparation and experimental techniques 3.1 Thin-film preparation by spin-coating 3.1.1 Films on glass slides 3.1.2 Films on silicon wafers 3.1.3 Reproducibility of sample preparation 3.1.4 Stability of thin film samples 3.1.5 Film thickness determination 3.1.6 Sample annealing experiments 3.2 Use of nanostructured electrodes – a novel approach 3.3 Poly(cis-1,4-isoprene) (PI) in porous media 3.4 Experimental techniques 3.4.1 Broadband Dielectric Spectroscopy (BDS) 3.4.1.1 Polarization 3.4.1.2 Dielectric relaxation 3.4.1.3 Debye relaxation 3.4.1.4 Non-Debye relaxation 3.4.1.5 Dielectric data in the time domain 3.4.1.6 Conductivity contribution 3.4.1.7 The distribution of relaxation times 3.4.1.8 BDS – summary 3.4.2 Spectroscopic Ellipsometry (SE) 3.4.3 AC-chip calorimetry (ACC) 4. Results and Discussion 4.1 Effect of sample geometry on measured dynamics 4.1.1 Introduction 4.1.2 Experimental details 4.1.3 Results and discussion 4.1.4 Summary 4.2 Dynamics of polystyrene in a wide range of molecular weights 4.2.1 Introduction 4.2.2 Experimental details 4.2.3 Results and discussion 4.2.4 Summary 4.3 Molecular dynamics of itraconazole confined in thin supported layers 4.3.1 Introduction 4.3.2 Experimental details 4.3.3 Results and discussion 4.3.4 Summary 4.4 Segmental and chain dynamics in nanometric layers of poly(cis-1,4-isoprene) 4.4.1 Introduction 4.4.2 Experimental details and data analysis 4.4.2.1 Sample preparation 4.4.2.2 Data analysis 4.4.3 Results and discussion 4.4.3.1 1- versus 2-D confinement of poly(cis-1,4-isoprene) 4.4.4 Summary 5 Conclusions 5.1 Dynamics in confinement – a wider perspective