Block copolymers are widely used commercially and so a complete understanding of these systems requires that the nature of the polymer interface, the effect of deformation and the interaction between polymer substituents are known. Triblock copolymers of poly(styrene-isoprene-styrene) were synthesised and used in a Small Angle Neutron Scattering (SANS) study of deformation (Ch. 3) . Three sets of samples were made and, of these, two sets were found to have degraded giving unexpected results (Ch. 3.2). The third set, SPH150 series, however, did exhibit the expected anisotropy on deformation (Ch. 3.3). In these samples, the extension parallel to the stretch direction was affine for all elongation ratios studied and, perpendicular to the stretch direction, the extension was non-affine. The interaction between polymer substituents was examined using SANS on an isotopic diblock copolymer of polystyrene to ascertain if the mixing of hydrogenous and deuterated species was ideal (Ch. 4) . The results obtained showed the mixing between these species could be assumed to be ideal. The nature of the polymer-polymer interface was studied on the CRISP reflectometer using poly(styrene- isoprene) diblock samples (Ch. 5) . The results obtained for unannealed samples showed that a 'pseudo- equilibrium' had been achieved in these samples which was lost on annealing.

The nanoindentation technique has been used to identify the interfaces between dissimilar materials and subsequently to evaluate the physical and mechanical properties across the interfaces. The interfaces could represent the interface (transition face) between oxidized and unoxidized polymers, the interface between rigid fiber and polymer matrix, or other similar situations. It is proposed to use a nanoindenter equipped with small spherical tip to indent across the interfaces of dissimilar materials. The proposed method has been validated by conducting a large number of virtual experiments through 3-dimensional finite element simulations, by varying the properties of the two dissimilar materials, including various combinations of modulus (E1/E2), yield strength (σy1/σy2), hardening index (n1/n2), interface sizes (R/T), Poisson’s ratio (ν), etc. The mechanical properties across the interfaces have been obtained, and a quantitative model for predicting the interface sizes has been established.

Molekulardynamik (MD) Simulationen wurden an zwei verschiedenen Systemen durchgeführt: 1. Grenzfläche zwischen Polyethylen und isotaktischem Polypropylen (PE-iPP) und 2. Zylindrische Mizellen, bestehend aus Tetradecyltrimethylammoniumbromid (C14TAB), in wässriger Lösung und an Fest-Flüssig-Grenzflächen. Die allgemeinen Schwierigkeiten bei der Simulation von Grenzflächen kristalliner Polymere wurden diskutiert und eine Methode für solche Simulationen vorgeschlagen. Diese Methode wurde zur epitaxialen Kristallisation von PE auf iPP benutzt. Experimentelle Ergebnisse der epitaxialen Kristallisation konnten durch die Simulation bestätigt werden. Ferner konnte vorhergesagt werden, dass PE bevorzugt auf einer iPP-Oberfläche mit hoher Methylgruppenkonzentration kristallisiert. Ebenso wurde durch die MD Simulation vorhergesagt, dass PE in der Grenzflächenregion von einer orthorhombischen zur monoklinischen Kristallstruktur wechselt. Die Simulationsdauer für die Mizellen betrug einige Nanosekunden. Die Ergebnisse für die Mizellen in wässriger Lösung stehen hierbei in guter Übereinstimmung mit experimentellen Werten. Im Widerspruch zur allgemein üblichen Vorstellung führte die Simulation der Mizellen zur Ausbildung eines Hohlraums in ihrer Mitte sowie zu einer inhomogenen Dichte des hydrophoben Mizellkerns. Dies wurde zum Teil der inhomogenen Verteilung der terminalen Methylgruppen im Mizellkern zugeschrieben. Zylindrische und halbzylindrische Mizellen wurden an den Paraffin/Wasser- und Gold/Wasser-Grenzflächen simuliert. / Molecular Dynamic (MD) simulation of two different systems was performed: 1) Polyethylene- isotactic Polypropylene (PE-iPP) interfaces and 2) cylindrical micelles formed by tetradecyl trimethylammonium bromide (C14TAB) molecules in aqueous solution and at solid liquid interfaces. The general difficulties of simulation of polymer crystalline interfaces were discussed and one method was proposed for such simulations. Thise method was used to simulate epitaxial crystallisation of PE on iPP. The experimental results on epitaxial crystallisation were confirmed by MD simulation and in addition epitaxial crystallisation of PE on iPP surface with high dencity of methyl groups was predicted. MD simulation also predicted that PE should change at the interfacial region from the orthorhombic to monoclinic crystalline structure. Several nanoseconds of life of cylindrical micelles were simulated. The simulation results for the micelle in aqueous solution were favourably compared with experimental results. In contradiction to the standard picture of an ionic micelle the simulated micelle formed hole in its centre and the density of the hydrophobic micelle core was inhomogeneous. This effect partially was explained by the inhomogeneous distribution of the terminal methyl groups in the micelle core. Cylindrical and half cylindrical micelles of C14TAB molecules were simulated at the paraffin- and gold-aqueous interfaces.

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When azobenzene-modified photosensitive polymer films are irradiated with light interference patterns, topographic variations in the film develop that follow the electric field vector distribution resulting in the formation of surface relief grating (SRG). The exact correspondence of the electric field vector orientation in interference pattern in relation to the presence of local topographic minima or maxima of SRG is in general difficult to determine. In my thesis, we have established a systematic procedure to accomplish the correlation between different interference patterns and the topography of SRG. For this, we devise a new setup combining an atomic force microscope and a two-beam interferometer (IIAFM). With this set-up, it is possible to track the topography change in-situ, while at the same time changing polarization and phase of the impinging interference pattern. To validate our results, we have compared two photosensitive materials named in short as PAZO and trimer. This is the first time that an absolute correspondence between the local distribution of electric field vectors of interference pattern and the local topography of the relief grating could be established exhaustively. In addition, using our IIAFM we found that for a certain polarization combination of two orthogonally polarized interfering beams namely SP (↕, ↔) interference pattern, the topography forms SRG with only half the period of the interference patterns. Exploiting this phenomenon we are able to fabricate surface relief structures below diffraction limit with characteristic features measuring only 140 nm, by using far field optics with a wavelength of 491 nm. We have also probed for the stresses induced during the polymer mass transport by placing an ultra-thin gold film on top (5–30 nm). During irradiation, the metal film not only deforms along with the SRG formation, but ruptures in regular and complex manner. The morphology of the cracks differs strongly depending on the electric field distribution in the interference pattern even when the magnitude and the kinetic of the strain are kept constant. This implies a complex local distribution of the opto-mechanical stress along the topography grating. The neutron reflectivity measurements of the metal/polymer interface indicate the penetration of metal layer within the polymer resulting in the formation of bonding layer that confirms the transduction of light induced stresses in the polymer layer to a metal film. / Azobenzolhaltige Polymere gehören zu einer Klasse funktionaler Materialien, bei denen durch ein äußeres Strahlungsfeld eine starke mechanische Reaktion ausgelöst werden kann. Durch die Bindung an das Polymerrückgrat können die Azobenzole, die unter UV-Belichtung eine Photoisomerisierung ausführen, was zum Teil drastische Effekte zur Folge hat. Unter Belichtung mit Intensitätsmustern, d.h. mit räumlich variierender Verteilung der Polarisation oder der Intensität des einfallenden Lichts verändert sich die Topographie der azobenzolhaltigen Filme, was zur Bildung von Oberflächengittern (engl. Surface Relief Gratings, SRG) führt. In dieser Arbeit wurde eine neue Methode vorgeschlagen, bei der das Verhalten elastischer/morphologischer Eigenschaften unter verschiedenen Belichtungsbedingungen, d.h. mit unterschiedlicher Verteilung der Polarisation und der Intensität in situ lokal als Funktion der Position entlang der SRG aufgenommen werden kann. Außerdem wurde hier vorgeschlagen, opto-mechanische Spannungen, die innerhalb der photosensitiven Polymerfilme während der Belichtung entstehen, mit Hilfe dünner aufgebrachter metallischen Schichten abzubilden und zu analysieren.