Non-equilibrium plasma modification of polymer surfaces in an oxygen atmosphere provides a highly efficient, solventless method of raising the surface energy. The chemical and physical effects of non-equilibrium plasma treatment on polymer surfaces have been investigated. Oxygen glow discharge and silent discharge treatment of several polymers (polypropylene, polystyrene, polyphenylene oxide and polycarbonate) has been shown to cause both surface oxidation and chain scission at the polymer surface. This generates low molecular weight oxidised material on the polymer surface which conglomerates into globular features due to the difference in surface energy between the oxidised material and the untreated polymer. These features can be removed by solvent washing. Generally silent discharge treatment generates more low molecular weight oxidised material whereas oxygen glow discharge treatment generates more non-soluble oxidised material. Crystalline polymers react at a slower rate than amorphous material. During the treatment of a model crystalline polymer (hexatriacontane) the plasma attacks the edges of the crystal, rather than the surface, due to the greater chain mobility at the edge. Non-equilibrium plasma treatment of both miscible and immiscible polymer blends were investigated. The size and distribution of the globular features formed were found to be dependent on the blend composition. For the immicible polymer blend, non-equilibrium plasma treatment reveals the blend morphology mi sing from the difference in reaction rates of the parent polymers.

I denna avhandling beskrivs tillverkning, karaktärisering och tillämpning av ett antal biomimetiska ytor. Biomimetik är att härma naturen och grundtanken är att titta på hur naturen löst liknande problemställningar. Två olika typer av modellsystem med inspiration från naturen har tagits fram för framtida tillämpningar inom bioanalys, biosensorer samt antifrysmaterial. Det ena typen av modellsystem innefattar fosforylerade ytor och det andra består av ytor som härmar antifrys(glyko)proteiner. Ytorna tillverkades av monolager av självorganiserande svavelorganiska molekyler och karaktäriserades före tillämpning med hjälp av ellipsometri, IR-spektroskopi, kontaktvinkelmätning och röntgenfotoelektronspektroskopi. Modellsystemen för att studera vattenfrysning på ytor inspirerades av antifrys(glyko)proteiner som bl.a. kan hittas i polarfiskar. Två modellsystem utvecklades och studerades med avseende på frysning av kondenserat vatten. Det ena designades att härma den aktiva domänen hos ett antifrysglykoproteiner (AFGP) och det andra härmade typ I antifrysproteiner (AFP I). Frysstudierna visade på signifi-kanta skillnader för AFGP-modellen jämfört med ett (OH/CH3) referenssystem med jämförbar vätbarhet, men inte för AFP Imodellen. Vattnet frös vid högre temperatur för AFGPmodellen. Modellsystemen med fosforylerade ytor inspirerades av fosforylering och biomineralisering. Två system utvecklades, ett med långa och ett med korta alkylkedjor på aminosyraanalogerna, både med och utan fosfatgrupp. En ny metod användes med skyddsgrupper på fosfaterna hos de långa analogerna innan bildandet av monolager. Skyddsgrupperna togs bort efter bildandet av monolager. Dessa monolager undersöktes också med elektrokemiska metoder och signifikant högre kapacitans observerades för de fosforylerade monolageren jämfört med de icke fosforylerade. / This thesis describes the preparation, characterization and application of a few biomimetic surfaces. Biomimetics is a modern development of the ancient Greek concept of mimesis, i.e. man-made imitation of nature. The emphasis has been on the preparation and characterization of two types of model systems with properties inspired by nature with future applications in bioanalysis, biosensors and antifreeze materials. One type of model system involves phosphorylated surfaces; the other consists of surfaces mimicking antifreeze (glyco)proteins. The surfaces were made by chemisorbing organosulfur substances to a gold surface into monomolecular layers, so called self-assembled monolayers (SAMs). The physicochemical properties of the SAMs were thoroughly characterized with null ellipsometry, contact angle goniometry, x-ray photoelectron spectroscopy and infrared spectroscopy prior to application. The work on antifreeze surfaces was inspired by the structural properties of antifreeze (glyco)proteins, which can be found in polar fish. Two model systems were developed and studied with respect to ice nucleation of condensed water layers. One was designed to mimic the active domain of antifreeze glycoproteins (AFGP) and the other mimicked type I antifreeze proteins (AFP I). Subsequent ice nucleation studies showed a significant difference between the AFGP model and a (OH/CH3) reference system displaying identical wetting properties, whereas the AFP I model was indistinguishable from the reference system. The model systems with phosphorylated surfaces were inspired from phosphorylations and biomineralization. Two systems were developed, short- and long-chained amino acid analogues, with and without a phosphate group. A novel approach with protected groups before attachment to gold were developed for the long-chained analogues. The protective groups could be removed successfully after assembly. The long-chained SAMs were evaluated with electrochemical methods and significantly higher capacitance values were observed for the phosphorylated SAMs compared to the non-phosphorylated.

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Over the past two decades, vibrational sum-frequency generation (VSFG) has been applied as a versatile technique for probing the structure and dynamics of molecules at surfaces and interfaces. The excellent surface specificity of the SFG allows for probing different kinds of liquid interfaces with no or negligible contribution from adjacent and much deeper bulk phase. VSFG spectroscopy has provided evidence that the structure of the water at interfaces is different from the bulk. With the ultrafast pulses, VSFG can also be used as a probe of ultrafast vibrational dynamics at interfaces. However, apart from a few pioneering studies, the extension of VSFG into time domain has not been explored extensively. Here VSFG is used as a probe of ultrafast vibrational dynamics of water at silica interfaces. Silica is an excellent model system for the solid phase where one can systematically vary the surface charge via bulk pH adjustment. The extension of the surface electric field, the interfacial thickness and surface accumulation of ions at a charged silica surface were studied using IR pump-VSFG probe spectroscopy. A vibrational lifetime (T1) of about 250 fs, similar to bulk H2O, was observed for the O-H stretch of H2O/silica interface when the silica surface is negatively charged. At the neutral surface, where the thickness of interfacial water is smaller than at the charged surface, the vibrational lifetime of O-H stretch becomes more than two times longer (T1~ 600 fs) due to the decreased number of neighboring water molecules, probed by SFG. The fast T1 at negatively charged surface begins to slow down by screening of the penetration of surface electric field via adding salt which suggests the primary reason for similar vibrational dynamics of water at charged interface with bulk water is the penetration of electric field. By decoupling of OH of HDO in D2O, a frequency dependent vibrational lifetime is observed with faster T1 at the red compared to the blue side of the hydrogen bond spectral region. This correlates with the redshift of the SFG spectra with increasing charged surface and is consistent with a theoretical model that relates the vibrational lifetime to the strength of the hydrogen bond network. / Chemistry

Important aspects of adhesion occur at interfaces, including structures that may be different from those in the bulk materials. However, probing the orientation of molecules in functional adhesives poses a significant challenge because adhesive molecules are always located at a buried interface. The limited penetration depth of surface-specific analysis prohibits the study of buried interfaces using those techniques. The large quantity of bulk molecules relative to the adhesive molecules interacting at the interface results in the bulk signal swamping out adhesive signal in bulk analysis techniques. An interface-specific technique is required to study functional adhesives. One such technique that has shown promise in recent years is Vibrational sum frequency generation (VSFG) spectroscopy. This technique is useful for studying interactions that occur at surfaces and interfaces because it selectively probes regions of broken inversion symmetry. Despite the ability of VSFG to isolate signal from a buried interface, a non-resonant signal that is produced simultaneously with the resonant signal corrupts the vibrational data of interest and greatly impedes reliable analysis of VSFG spectra. Over the last several years, researchers have experimentally removed non-resonant signal by delaying the upconverting pulse with respect to the initial excitation. Obtaining reliable results from VSFG data depends upon complete removal of non-resonant signal. However, complete removal of non-resonant signal presents a challenge because it can be present in spectra even when the indicators of non-resonant signal are absent. By taking advantage of polarization selection rules for VSFG and the differing symmetry of an azimuthally isotropic film and an azimuthally non-isotropic substrate, spectra containing non-resonant signal can be easily identified. These and other advances in VSFG methodology have enabled the study of surface and interfacial systems of interest. In a study of the effects of plasma treatment on polystyrene thin films, plasma exposure was found to affect not only the free surface but also portions of the sub-surface polymer, challenging previous assumptions that plasma effects are constrained to the free surfaces of materials. The next step is to use VSFG to study functional adhesives under known amounts of applied stress. An apparatus is in place to simultaneously collect VSFG spectra during mechanical testing of a functional adhesive, and in preliminary studies, an increase in VSFG non-resonant signal has been observed when a pulling force is applied to the adhesive bond.