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The aim of this thesis work was to systematically investigate the physico-chemical properties of polyelectrolyte complexes (PECs) formed by bottle brush and linear polyelectrolytes in solution and at solid / liquid interfaces. Electrostatic self-assembly of oppositely charged macromolecules in aqueous solution is a versatile strategy to construction of functional nanostructures with easily controlled properties. Bottle brush architecture, introduced into the PEC, generates a number of distinctive properties of the complexes, related to a broad range of application, such as colloidal stability and protein repellency to name a few. To utilize these materials in a wide range of applications e.g. drug delivery, the understanding of the effects of polymer architecture and solution parameters on the properties of bottle brush PECs is of paramount importance. This thesis constitutes a systematic investigation of PECs formed by a series of cationic bottle-brush polyelectrolytes and a series of anionic linear polyelectrolytes in aqueous solution. The focus of the first part of the thesis was primarily on formation and characterization of PECs in solution, whereas the adsorption properties and adsorption kinetics of bottle-brush polyelectrolytes and their complexes was investigated in the second part of the thesis work. In particular, effects of the side-chain density of the bottlebrush polyelectrolyte, concentration, mixing ratio and molecular weigh of the linearpolyelectrolyte on formation, solution properties, stability and adsorption of PECs were addressed. The pronounced effect of the side-chain density of the bottle-brush polyelectrolyte on the properties of stoichiometric and nonstoichiometric PECs was demonstrated. Formation of PECs by bottle-brush copolymers with high density of side-chains results in small, watersoluble, molecular complexes having nonspherical shape, independent of concentration. Whereas formation of PEC-aggregates was revealed by bottle-brush polyelectrolytes with low side chain density, the level of aggregation in these complexes is controlled by polyelectrolyte concentration. The structure of the PECs formed with low molecular weight polyanions is consistent with the picture that several small linear polyelectrolyte molecules associate with the large bottle-brush. In contrast, when complexation occurs between polyanions of high molecular weigh and the bottle-brush polymers considerably larger PECs are formed, consistent with several bottle-brush polymers associating with one high molecular weight polyanion. / QC 20110516

The focus in this thesis has been to gain a fundamental understanding of how different type of salts affect preadsorbed polyelectrolytes, both natural and synthetic. The knowledge from the fundamental work is then applied on a commercial system to investigate if the efficiency can be enhanced. We built thin films using the synthetic polyelctrolytes by using layer-by layer (LbL) deposition. The formed film is commonly known as a polyelectrolyte multilayer. The LbL method allows the incorporation of proteins, polymers, polyelectrolytes with different functions and so on within the film, thus achieving multilayers with different functions. The major measuring technique used within this thesis is the quartz crystal microbalance with dissipation (QCM-D), which measures mass adsorbed on a surface including the trapped solvent and the viscoelastic properties of an adsorbed film. The QCM-D measurements were complemented with an optical technique, dual polarization interferometry (DPI), which measures the change in refractive index and thickness. From these parameters the dry mass and relative water content of the film can be calculated. The Atomic Force Microscopy (AFM) further gave information about forces acting between preadsorbed films. We investigated the effect of salt on synthetic polyelectrolyte poly(allylamine hydrochloride)/poly(sodium 4-styrenesulfonate) built with the LbL technique, thus forming polyelectrolyte multilayers. We concluded that the multilayer build-up was linear and that the internal structure of the multilayer is of a compact and rigid nature. However, the type of rinsing protocol (termination of adsorption by: salt, water and salt first followed by water) has a significant effect on the outer layer of the formed multilayer. Interestingly, the structural changes only applied when poly(allylamine hydrochloride) was at the outermost layer and the most significant when water was used. We suggest that it is only the top layer that swells due to the removal of counterions resulting in increased intrachain repulsion. We further performed two-layer model calculations with the Voight model to confirm the QCM-D results as well as a novel two layer model simulation for the DPI data in order to resolve the thickness. The model calculations were in good agreement with each other thus we concluded that only the outer layer swells for this particular multilayer system. In a related experiment we studied the adsorption of bovine submaxillary mucin (BSM), which has an important mucousal function, to different thiol modified gold surfaces as well as the effect of electrolytes (NaCl, CaCl2, LaCl3) on preadsorbed mucin to a hydrophobic thiol-modified Au surface. The salt induced an expansion at low concentrations; higher concentrations resulted in a compaction. Increasing the valence of the counter ion resultedin a compaction at low concentrations. The structural change of preadsorbed BSM was reversible for NaCl, partially reversible for CaCl2 and irreversible for LaCl3. Interestingly, the swelling of BSM could not be fully understood by using the QCM-D and thus AFM force curves of the same system were taken and the results showed that NaCl does decrease the tail length due to the effective screening of charged sites within the BSM molecule. Increasing the valence resulted in a notable compaction already at very low concentrations suggesting that the ions bind to the anionic sites on BSM. In the last work we attempted to combine the gained knowledge from the previous studies by using the LbL-buildup on an actual commercial health care application. The above-mentioned mutlilayer were used to coat polystyrene wells in order to increase the binding of immunoglobulin (IgG). The main goal was to increase the sensitivity of the conventional enzymelinked immunosorbent spot assay (ELISpot) and subsequently the modified polystyrene wells were used with the ELISpot test with human peripheral blood mononuclear cells (PBMC) to measure the cytokine response. We suggested that the main driving force for adsorption for IgG on a PAH terminated multilayer is electrostatic attraction, whereas on PSS terminated multilayer the driving force is hydrophobic. Further, we suggested that IgG  does not overcharge the surface and the linearity of the multilayer build-up is not altered when IgG is incorporated within the multilayer structure. We concluded that the cytokine response (spots) on the built multilayers regardless thickness or adsorbed IgG is significantly less than the regular polyvinyldiene fluoride (PVDF) backed ELISpot wells. We suggested that due to the compact and rigid nature of the PAH/PSS multilayer structure it is unable to form the kind of three-dimensional antibody-binding support found in the PVDF membrane. PSS terminated PAH/PSS multilayer did not induce any cytokine response whereas PAH terminated did, which suggests that PSS totally covers the surface from the cells point of view. / QC20100705

Paper and board are hydrophobized (sized) to control the spreading and absorption of waterbased inks and retard the absorption and edge penetration of liquid packaging by aqueous liquids. Alkenyl ketene dimers (AKD) and alkenyl succinic anhydride (ASA) are synthetic sizing agents that are generally used under neutral or slightly alkaline papermaking conditions. The overall objective of this thesis is to improve understanding of the internal sizing of paper and board by AKD and ASA by establishing a link between the sizing mechanism on one hand, and properties of sized papers, such as surface chemistry, wettability and friction, on the other. Fundamental research has been conducted in parallel with more applied research on laboratory and pilot papers. Significant effort has been expended to study the spreading behavior of AKD. The main instrument to characterize the surface chemical composition of AKD and ASA sized papers was X-ray photoelectron spectroscopy (XPS). By combination with time-of-flight secondary ion mass spectrometry (ToF-SIMS) we have been able to determine the lateral distribution and the chemical state of the sizing agent at the paper surface. Combined with contact angle measurements using liquids with different surface tensions, and other methods to analyze the amounts of size in paper, this has enabled us to obtain a deeper knowledge of the sizing mechanisms of AKD and ASA. The results indicate a definitive relationship between the redistribution of AKD at the surface of pilot papers and the drying profile used during papermaking. However, the spreading was not complete, as also seen on a model surface. Further spreading of AKD was shown to occur via surface diffusion in the form of an autophobic monolayer precursor. The spreading rate increased linearly with temperature and showed an inverse proportionality with respect to the melting point of the AKD. This monolayer spreading is relatively slow the diffusion coefficient being of the order 10-11 m2/s. AKD spreading was not hindered by hydrolyzed AKD (ketone) that spread as well. Moreover, AKD spread on the surface of crystalline calcium carbonate. In laboratory papers, the extractives present on CTMP fiber surfaces appeared to have enhanced the spreading of AKD when the fibers were in water. In spite of a slightly lower retention, ASA covered the surface of unfilled and PCC-filled pilot papers to a significantly higher extent than AKD. The ASA sized papers, however demonstrated slightly lower resistance to water. This was attributed to formation of hydrolyzed ASA products. The results obtained confirm the proposed sizing mechanism for ASA, where the hydrolyzed ASA plays a key role. The sizing level of these papers stored wrapped in aluminium foil at 23 °C and 5O %RH was nearly unchanged over prolonged storage time. In contrast, the papers exposed to ambient conditions suffered from sizing loss, most likely due to hydrolysis and migration. The reduction of the sizing degree was higher for the AKD than ASA sized unfilled papers and the catalytic effect of PCC contributed to the hydrolysis of AKD in PCC-filled papers. As expected, the use of sizing agent reduced the surface energy of paper. The higher the sizing degree of paper the lower the surface energy, and thus the higher the resistance to wetting. This was particularly seen in the contact angles with ethylene glycol having a lower surface tension than water. AKD significantly decreased the friction between unfilled papers, whereas ASA had no impact. This difference was attributed to surface chemical composition. Friction reduction for the AKD sized papers started at the AKD coverage normally found in paper produced for low water absorption. As expected, PCC filler increased paper-to-paper friction. / Papper och kartong hydrofoberas (limmas) för att kontrollera spridning och absorption avvattenbaserade tryckfärger och hindra kantinträngning av vattenbaserade vätskor ivätskekartong. Alkylketendimer (AKD) och alkylbärnstensyra anhydrid (ASA) är syntetiskahydrofoberingsmedel som allmänt används under neutrala eller något alkaliska förhållandenvid papperstillverkning.Arbetets övergripande målsättning var att förbättra förståelse för mäldhydrofobering avpapper och kartong med AKD och ASA genom att upprätta ett samband mellanhydrofoberingsmekanism på ena sida och ytkemi hos hydrofoberat papper och dessvätningsförmåga och friktion på den andra sidan. Grundläggande studier parallellt med mertillämpade undersökningar på laboratorie- och pilotpapper har utförts. En betydande strävanhar använts för att studera spridning av AKD. Huvudinstrumentet för att karakterisera kemisksammansättning av ytan av pilotpapper hydrofoberade med AKD och ASA var röntgenfotoelektron spektroskopi (XPS). Genom att kombinera det med sekundär jonmasspektrometri (ToF-SIMS) har lateral fördelning och kemiskt tillstånd av AKD och ASAvid en yta av papper kunnat bestämmas. Kombinerat med mätningar av kontaktvinkel medvätskor med olika ytspänning och andra metoder för att analysera halten avhydrofoberinsgmedel i papper har gjort det möjligt att erhålla djupare kunskap omhydrofoberingsmekanismer av AKD och ASA.Resultaten indikerar en klar koppling mellan omfördelning av AKD på ytan av pilotpapperoch torkningsprofil vid papperstillverkning. Emellertid, spridningen var inte fullständig, vilketvar fallet även på modellytor. Fortsatt spridning av AKD visades ske som ytdiffusion i formav ett autofobiskt monoskikt (precursor film). Spridningshastigheten ökade linjärt medtemperatur och visade omvänd proportionalitet med avseende på AKD:s smältpunkt. Dennamonoskiktspridning är relativt långsam, diffusionshastighet är i storleksordningen 10-11 m2/s.Hydrolyserat AKD (keton) hindrade inte AKD:s spridning utan spred även den. Dessutomspred AKD på ytan av kristallina kalciumkarbonat. I laboratoriepapper är extraktivämnennärvarande på ytor av CTMP fiber och tycktes ha förbättrat AKD:s spridning när fibrerna varunder vatten.ivTrots något lägre retention täckte ASA ytan av icke-fyllda och PCC-fyllda papper tillsignifikant högre grad än AKD. ASA-papperen visade dock något lägre motstånd mot vatten.Detta var hänvisat till bildning av hydrolyserade ASA-produkter. De uppnådda resultatenbekräftar den föreslagna hydrofoberingsmekanismen för ASA, där hydrolyserat ASA spelaren avgörande roll. Hydrofoberingsgraden av papper lagrade inlindade i aluminiumfolie vid23 °C och 50 RH var nästan oändrad över den förlängda lagringstiden. Som motsatsgenomgick papperen som exponerats mot omgivande atmosfärsförhållanden genomgick enminskning av hydrofoberingsgraden, troligen på grund av hydrolys och migrering. Minskningav hydrofoberingsgraden var större för icke-fyllda papper av AKD än av ASA. PCC:skatalytiska effekt bidrog till hydrolys av AKD i PCC-fyllda papper.Som förväntat reducerade användning av hydrofoberingsmedel reducerade ytenergin avpapper. Ju högre hydrofoberingsgrad desto lägre var ytenergin och därmed desto högremotstånd mot vätning. Detta sågs särskilt i kontaktvinklar med etylenglykol som har lägreytspänning än vatten.AKD minskade signifikant friktionen mellan icke-fyllda papper, medan ASA inte hadeinverkan. Denna skillnad hänfördes till skillnad i ytsammansättning. Minskning av friktion förAKD-hydrofoberade papperen påbörjades vid en sådan yttäckning av AKD som är normaltför papper tillverkat för låg vattenabsorption. Som förväntat ökade PCC-fyllmedel friktionenmellan papperen. / QC 20100817

The objective of this work was to investigate the behaviour of some model surfactants used in the deinking process, namely, sodium oleate and two ethoxylated nonionic surfactants (C12E6 and C14E6) as well as to investigate the suitability of various model substrates for mimicking interactions in technical systems. The influence of the adsorption to the air � water interface has been measured by means of equilibrium and dynamic surface tension measurements, as well as foaming experiments. It was found that the solution pH and temperature influenced the dynamic and equilibrium surface tensions and the value of the cmc. Equilibrium surface tension measurements were also performed with mixtures of sodium oleate and nonionic surfactants and a strong synergistic effect was obtained, which means that a greater surface tension reduction can be obtained at lower surfactant concentrations. The foaming experiments, carried out with a Foam Scan Apparatus, showed an approximately constant total foam volume for both the pure surfactant systems and for the mixtures. In addition, the foam was slightly more stable for the mixtures than for the pure components. Friction and surface forces between solid surfaces in liquid were studied using the atomic force microscope (AFM) from which inferences about the adsorption to these interfaces could be drawn. The AFM measurements were performed with the colloidal probe technique using cellulose as colloidal probe and an alkyd resin as a model ink surface. Mica and silica were both used as models for hydrophilic surfaces. Adsorption was observed on the alkyd resin, both with sodium oleate and with C12E6. The adsorption was registered both as a change in normal surface force interaction and as a strong reduction in friction force and friction coefficient at increasing surfactant concentration. The magnitude of the friction force was observed to be dependent on the adhesion and varied monotonically with the surface roughness. Measurements of adhesion and friction forces in air were performed, and the same conclusions about the effect of roughness were drawn. Finally the friction force behaviour appears to be similar if the adhesion is caused by a vapour bridge in liquid, or by a liquid bridge in air, where the formation of a capillary bridge in air is strongly dependent on the relative humidity. / QC 20100923

This doctoral thesis comprises three studies dealing with water-based flexography on polymer-coated boards, which have been presented in the five papers included at the end of the thesis. The first study (covered in three papers) presents results from characterisation of a matrix of water-based inks with respect to their rheology, surface tension, wetting, and fulltone printing performance on PE-coated board. The commercial water-based inks used vary in type of pigment and acrylic vehicle, and in pigment/vehicle mixing proportions. For all mixing proportions, the inks were shear thinning, with viscosity increasing strongly with content of solution (versus emulsion) polymer in the vehicle. Increasing amount of solution polymer also gave the indirect consequence of lower surface tension values. The wet ink amount transferred to the board and the resulting print uniformity responded sensitively to ink formulation and could be correlated to the corresponding changes in these two ink properties. Transferred amount correlated well with ink plastic viscosity and static surface tension, exhibiting a maximum at intermediate values of both. Print mottle decreased with increasing content of solution polymer, principally due to the associated increase in low-shear viscosity and decreased surface tension, both serving to reduce substrate dewetting. In the second study, the effect of corona discharge treatment of PE-coated board on its surface chemistry and print resistance properties was evaluated. The increase in total surface energy, due to its polar component, with increasing corona level was strongly correlated to surface oxidation fraction from XPS. AFM revealed oxidised material nano-mounds, which increased in size and substrate coverage with corona level. Wet rub resistance (with water) first increased for lower corona dosages before decreasing at higher dosages. This worsened water resistance at higher dosages is presumably due to the oxidised material dissolved and dispersed in the ink film. The third study presents results from another set of water-based acrylic inks printed on boards coated with PE, OPP and PP. Print quality and resistance properties, though dependent on the polymer type, were strongly influenced by the choice of emulsion polymer and presence of silicone additive in the vehicle, with corona treatment level playing a lesser role. The emulsion polymer giving best resistance performance was generally found to give poorest press performance and visual appearance. Again the trends could be understood in terms of wet ink surface tension (versus substrate surface energy), dictating print uniformity, and dry print surface energy (and swellability), dictating resistance properties. / QC 20100916

This thesis claims a relationship between the film splitting sound emission from the printing press nip and the dynamic interaction occurring there between ink, fountain solution and substrate in offset lithography. The film splitting sound derives from the cavitation formed by the pressure drop in the second half of the print nip flow passage. As the ink film is strained, the cavities expand and eventually implode into breaking filaments at the nip exit, while emitting a partly audible, broadband, high frequency, noisy sound. A free-field microphone, A/D-converter and laptop computer were used to record pressure signals in the frequency range of 10 Hz to 50 kHz emitted by a variety of printing instruments and presses for a range of offset ink and paper types. After signal acquisition and filtering two signal averages of power and frequency were estimated. This average power increased with increasing loads of sheet-fed offset ink on an ink distributor, in accordance with a mass-conservation model developed. The behaviour of average frequency and power over different ink load ranges indicated transitions between different flow regimes. A glossy fine-coated paper gave higher average power than a corresponding matte paper during printing with such inks on a laboratory device, possibly due to an air sealing effect. The sound from tack measurements with the Deltack instrument during setting of heat-set offset inks printed on MWC papers showed a relation between the measured tack rise and average power, reflecting changes in splitting mechanism during the course of setting. With the Hydroscope instrument the interaction between these heat-set inks and fountain solution was studied, with the measured tack and sound emission displaying a clear, but non-linear, correlation. A heat-set offset pilot trial showed that the acoustic response from the printing nip sensitively and systematically detected changes in (LWC) paper type, optical density, ink-fount balance, and press stability. Pilot trials of cold-set offset inks on newsprint by sheet-fed presses indicated a strong correlation between evolution in average power, optical density and fountain solution consumption during the first thousand sheets normally needed for stabilisation. Acoustic measurements of ink film splitting have, aside from the laboratory studies performed by one Japanese group, previously received little attention, with the current study showing that a great deal of information useful to the printer can be accessed from this sound emission. Although the detailed mechanisms for ink film splitting have to be further studied and supported by mathematical simulation, the sensitivity of the acoustic method recommends its implementation for monitoring and control of offset printing. / QC 20100928