For more than 70 years, understanding of the mechanism of particle nucleation in emulsion polymerization has been one of the most challenging issues in heterophase polymerization research. Within this work a comprehensive experimental study of particle nucleation in emulsion polymerization of styrene at 70 °C and variety of conditions has been performed. To follow the onset of nucleation, on-line conductivity measurements were applied. This technique is highly sensitive to the mobility of conducting species and hence, it can be employed to follow aggregation processes leading to particle formation. On the other hand, by recording the optical transmission (turbidity) of the reaction mixture particle growth was followed. Complementary to the on-line investigations, off-line characterizations of the particle morphology and the molecular weight have been performed. The aim was to achieve a better insight in the processes taking place after starting the reaction via particle nucleation until formation of colloidally stable latex particles. With this experimental protocol the initial period of styrene emulsion polymerization in the absence as well as in the presence of various surfactants (concentrations above and below the critical micellization concentration) and also in the presence of seed particles has been investigated. Ionic and non-ionic initiators (hydrophilic and hydrophobic types) have been applied to start the polymerizations. Following the above algorithm, experimental evidence has been obtained showing the possibility of performing surfactant-free emulsion polymerization of styrene with oil-soluble initiators. The duration of the pre-nucleation period (that is the time between starting the polymerization and nucleation) can be precisely adjusted with the initiator hydrophobicity, the equilibration time of styrene in water, and the surfactant concentration. Spontaneous emulsification of monomer in water, as soon as both phases are brought into contact, is a key factor to explain the experimental results. The equilibration time of monomer in water as well as the type and concentration of other materials in water (surfactants, seed particles, etc.) control the formation rate and the size of the emulsified droplets and thus, have a strong influence on the particle nucleation and the particle morphology. One of the main tasks was to investigate the effect of surfactant molecules and especially micelles on the nucleation mechanism. Experimental results revealed that in the presence of emulsifier micelles the conductivity pattern does not change essentially. This means that the presence of emulsifiers does not change the mechanism of particle formation qualitatively. However, surfactants assist in the nucleation process as they lower the activation free energy of particle formation. Contrary, seed particles influence particle nucleation, substantially. In the presence of seed particles above a critical volume fraction the formation of new particles can be suppressed. However, micelles and seed particles as absorbers exhibit a common behavior under conditions where monomer equilibration is not allowed. Results prove that the nucleation mechanism comprises the initiation of water soluble oligomers in the aqueous phase followed by their aggregation. The process is heterogeneous in nature due to the presence of monomer droplets. / Polymere dominieren unsere Welt. Die natürlich vorkommenden Polymeren, wie Proteine, Polynukleotide, und Polysaccharide, sind nötig um das Leben zu erhalten. Ebenso wichtig sind die kommerziell erhältlichen Makromoleküle. Beides sind Bausteine, um Materialien zu konstruieren, welche man in beiden Welten finden kann- der natürlichen und der „Mensch-gemachten“ Welt. Unter den verschiedenen Polymerisationsmethoden hat sich die Emulsions-polymerisation zu einem weit verbreiteten Prozess entwickelt. Die Emulsionspolymerisation ist ein einzigartiger Polymerisationsprozess, bei dem ein Monomer oder ein Gemisch von Monomeren in einem wässrigen Medium polymerisiert wird. Dabei entsteht eine Dispersion von Polymeren, welche auch als Latex bezeichnet wird. Derzeit werden mehrere Millionen Tonnen von synthetischen Latices mit Hilfe der Emulsionspolymerisation hergestellt. Diese finden zum Beispiel Verwendung als synthetische Gummi, Latexschaum, Latexfarben, Papierbeschichtungen und Klebstoffen. Außerdem findet man sie auch bei Spezialanwendungen, wie Diagnosetests, Pharmakotherapien und chromatographischen Trennmethoden. Trotz der Vielzahl von industriellen Anwendungen, sollten all jenen, die sich mit Emulsionspolymerisation beschäftigen, den wissenschaftlichen und technologischen Herausforderungen, die sich stellen, bewusst sein. Die wichtigsten Fragen beim Umgang mit der Emulsionspolymerisation beinhalten das Verständnis des Prozesses der Partikelbildung und des Partikelwachstums. Die vorliegende Dissertation beschäftigt sich mit der Frage der Keimbildungs-etappe in Emulsionspolymerisationen. Die Untersuchungen wurden mit Hilfe eines on-line Leitfähigkeitsmessverfahren sowie einigen off-line analytischen Experimenten durchgeführt. Basierend auf den klaren experimentellen Daten, wurde ein besserer Einblick in die tatsächlichen Zustände des Polymerisationssystems, von der Zeit der neu geboren Kerne bis zu endgültig stabilisierten Teilchen, gewonnen.

The creation of complex polymer structures has been one of the major research topics over the last couple of decades. This work deals with the synthesis of (block co-)polymers, the creation of complex and stimuli-responsive aggregates by self-assembly, and the cross-linking of these structures. Also the higher-order self-assembly of the aggregates is investigated. The formation of poly-2-oxazoline based micelles in aqueous solution and their simultaneous functionalization and cross-linking using thiol-yne chemistry is e.g. presented. By introducing pH responsive thiols in the core of the micelles the influence of charged groups in the core of micelles on the entire structure can be studied. The charging of these groups leads to a swelling of the core and a decrease in the local concentration of the corona forming block (poly(2-ethyl-2-oxazoline)). This decrease in concentration yields a shift in the cloud point temperature to higher temperatures for this Type I thermoresponsive polymer. When the swelling of the core is prohibited, e.g. by the introduction of sufficient amounts of salt, this behavior disappears. Similar structures can be prepared using complex coacervate core micelles (C3Ms) built through the interaction of weakly acidic and basic polymer blocks. The advantage of these structures is that two different stabilizing blocks can be incorporated, which allows for more diverse and complex structures and behavior of the micelles. Using block copolymers with either a polyanionic or a polycationic block C3Ms could be created with a corona which contains two different soluble nonionic polymers, which either have a mixed corona or a Janus type corona, depending on the polymers that were chosen. Using NHS and EDC the micelles could easily be cross-linked by the formation of amide bonds in the core of the micelles. The higher-order self-assembly behavior of these core cross-linked complex coacervate core micelles (C5Ms) was studied. Due to the cross-linking the micelles are stabilized towards changes in pH and ionic strength, but polymer chains are also no longer able to rearrange. For C5Ms with a mixed corona likely network structures were formed upon the collapse of the thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm), whereas for Janus type C5Ms well defined spherical aggregates of micelles could be obtained, depending on the pH of the solution. Furthermore it could be shown that Janus micelles can adsorb onto inorganic nanoparticles such as colloidal silica (through a selective interaction between PEO and the silica surface) or gold nanoparticles (by the binding of thiol end-groups). Asymmetric aggregates were also formed using the streptavidin-biotin binding motive. This is achieved by using three out of the four binding sites of streptavidin for the binding of one three-arm star polymer, end-functionalized with biotin groups. A homopolymer with one biotin end-group can be used to occupy the last position. This binding of two different polymers makes it possible to create asymmetric complexes. This phase separation is theoretically independent of the kind of polymer since the structure of the protein is the driving force, not the intrinsic phase separation between polymers. Besides Janus structures also specific cross-linking can be achieved by using other mixing ratios. / In den letzten Jahrzehnten war die Herstellung von komplizierten Polymerstrukturen ein wichtiges Forschungsthema für Polymerchemiker. Diese Arbeit behandelt die Synthese von (Blockco-)Polymere, die Herstellung von komplexen und stimulus-responsiven Aggregaten (Mizellen) durch Selbstorganisation, sowie die Vernetzung dieser Strukturen. Auch die Anordnung dieser Mizellen zu Aggregaten mit höherer Ordnung wurde untersucht. Zum Beispiel wird die Bildung von Poly(2-oxazolin) basierter Mizellen in wässriger Lösung und die gleichzeitige Funktionalisierung und Vernetzung dieser Mizellen mittels Thiol-In-Chemie beschrieben. Durch die Einführung von pH-responsiven Gruppen in den Kern der Mizellen konnte der Einfluss von geladenen Gruppen im Kern auf das gesamte Aggregat untersucht werden. Das Einführen von Ladung führt zum Quellen des Mizellkerns und damit zu einer niedrigeren lokalen Konzentration von wasserlöslichem Poly(2-ethyl-2-oxazolin) (PEtOx). Diese niedrigere Konzentration ergibt eine Verschiebung des Trübungspunkt dieses Typ I thermoresponsiven Polymers zu höheren Temperaturen. Wenn die Ausdehnung des Kerns nicht erfolgt, z.B. in Anwesenheit einer hohen Salzkonzentration, findet dieser Effekt nicht statt. Ähnliche Strukturen können mithilfe von Mizellen mit komplexen Koazervatkern (English: Complex Coacervate Core Micelles, C3Ms) durch die Interaktion zwischen Polymeren mit negativ und positiv geladenen Blöcken hergestellt werden. Der Vorteil dieser Strukturen ist, dass zwei verschiedene stabilisierende Polymerblöcke in einem Aggregat vereint werden können, was zur Bildung einer Vielzahl noch komplizierterer Strukturen und zu mehr Responsivität führen kann. Mithilfe von Blockcopolymeren, bestehend aus jeweils einen polyionischen Block und einem neutralen Block (z.B. PEtOx, PEO oder poly(N-isopropylacrylamid) (PNIPAAm)), konnten C3Ms hergestellt werden, in denen zwei neutrale Polymere vereint wurden. Es konnte gezeigt werden, dass diese Polymere sowohl gemischt als auch phasensepariert vorliegen können (letzteres ergibt Janus Mizellen), abhängig welche Polymere gewählt werden. Durch Vernetzung im Kern konnten die Mizellen stabilisiert und fixiert werden (C5Ms). Die Selbstanordnung dieser vernetzten Mizellen zu größeren Aggregaten wurde untersucht. Wenn eine Lösung mit vernetzten Mizellen über den Trübungspunkt von PNIPAAm erhitzt wurde, bildeten sich Netzwerke aus Mizellen mit einer gemischten Korona, während Janus Mizellen sich zu wohldefinierten Aggregaten höherer Ordnung anordneten. Weiterhin konnte gezeigt werden, dass Janus Mizellen sich auf der Oberfläche von anorganischen Nanopartikeln anlagern können; z.B. durch die selektive Wechselwirkung zwischen PEO und Silica oder durch die Adsorption von Thiolgruppen auf Gold-Nanopartikeln. Asymmetrische Aggregate konnten auch mithilfe des Streptavidin-Biotin Komplexes erhalten werden. Durch das Binden der Biotin-Endgruppen eines dreiarmigen Sternpolymeren an eine Streptavidin-Einheit und anschließende Belegung der verbliebenen Bindungsstelle mit der Biotin-gruppe eines Homopolymers, können sehr spezifisch zwei verschiedene Polymere in einem Janus Aggregat vereint werden. Auch die Vernetzung des Streptavidins kann erzielt werden, indem andere Mischverhältnisse gewählt werden.

No description available.

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.

The synthesis and polymerization of macromonomers containing a polymerizable styrene head group and a tail of ethylene oxide derivatives of different character were investigated. The synthesis of macromonomers was based on living anionic polymerization of oxiranes. Two monomers were used: 1-ethoxyethyl glycidyl ether (glycidol acetal), which after hydrolysis forms hydrophilic glycidol blocks and glycidyl phenyl ether forming hydrophobic blocks. Polymerizable double bonds were introduced by terminating the living chain with p-(chloromethyl)styrene. However, MALDI-TOF-MS end group analysis showed that all synthesized macromonomers were a mixture of the macromonomer and the non-functionalized oligomer. The degree of functionalization varied from 55 to 75 %. The obtained macromonomers showed amphiphilic properties and formed micelles in water. The determined critical micellization (CMC) concentration for poly(glycidol) macromonomer (DP = 50) was ca. 10 g/L, while the poly(glycidol) block macromonomers with hydrophobic spacer showed CMC on the level 0,7 g/L. The conventional free radical and controlled free radical polymerisation (ATRP) were used for preparation of polymacromonomers with different properties. The radical polymerization of the macromonomers was carried out in water using AVA as initiator and in the mixture of water/benzene (10/1 v/v) using AIBN. Core-shell polymers of different character and molar masses with polydispersity indices from 1,4 -3,0 were obtained. The ATRP carried out in water using PEO macroinitiator led to polymacromonomers with polydispersity indices from 1,1 to 1,3 and desiried molecular weight. In all cases the conversion of macromonomer (able to polymerization) was close to 100%. The polymerization product could easily be separated from the unable to reaction residue.

The synthesis and polymerization of macromonomers containing a polymerizable styrene head group and a tail of ethylene oxide derivatives of different character were investigated. The synthesis of macromonomers was based on living anionic polymerization of oxiranes. Two monomers were used: 1-ethoxyethyl glycidyl ether (glycidol acetal), which after hydrolysis forms hydrophilic glycidol blocks and glycidyl phenyl ether forming hydrophobic blocks. Polymerizable double bonds were introduced by terminating the living chain with p-(chloromethyl)styrene. However, MALDI-TOF-MS end group analysis showed that all synthesized macromonomers were a mixture of the macromonomer and the non-functionalized oligomer. The degree of functionalization varied from 55 to 75 %. The obtained macromonomers showed amphiphilic properties and formed micelles in water. The determined critical micellization (CMC) concentration for poly(glycidol) macromonomer (DP = 50) was ca. 10 g/L, while the poly(glycidol) block macromonomers with hydrophobic spacer showed CMC on the level 0,7 g/L. The conventional free radical and controlled free radical polymerisation (ATRP) were used for preparation of polymacromonomers with different properties. The radical polymerization of the macromonomers was carried out in water using AVA as initiator and in the mixture of water/benzene (10/1 v/v) using AIBN. Core-shell polymers of different character and molar masses with polydispersity indices from 1,4 -3,0 were obtained. The ATRP carried out in water using PEO macroinitiator led to polymacromonomers with polydispersity indices from 1,1 to 1,3 and desiried molecular weight. In all cases the conversion of macromonomer (able to polymerization) was close to 100%. The polymerization product could easily be separated from the unable to reaction residue.

No description available.

Even in times of renewable energy revolution fossil fuels will play a major role in energy supply, transportation, and chemical industry. Therefore, increasing demand for crude oil will still have to be met in the next decades by developing new oil re-serves. To cope with this challenge, companies and researchers are constantly seeking for new methods to increase the recovery factor of oil fields. For that reason, many enhanced oil recovery (EOR) methods have been developed and applied in the field. EOR methods alter the physico-chemical conditions inside the reservoir. One possibility to achieve this is to inject an aqueous solution containing special chemicals into the oil-bearing zone. Polymers, for example, increase the viscosity of the injected water and hence improve the displacement of the oil to the production well. The injection of surfactant solutions results in reduced capillary forces, which retain the oil in the pores of the reservoir. Some surfactants form viscoelastic solutions under certain conditions. The possibil-ity to apply those solutions for enhanced oil recovery has been investigated by some authors in the last years in low salinity brines. Reservoir brines, however, often contain high salt concentrations, which have detrimental effects on the properties of many chemical solutions applied for EOR operations. The Triphenoxymethane derivatives, which were the subject of study in this thesis, form viscoelastic solutions even in highly saline brines. The aim of this thesis was to investigate the efficiency and the mode-of-action of this new class of chemical EOR molecules with respect to oil mobilization in porous media.

Even in times of renewable energy revolution fossil fuels will play a major role in energy supply, transportation, and chemical industry. Therefore, increasing demand for crude oil will still have to be met in the next decades by developing new oil re-serves. To cope with this challenge, companies and researchers are constantly seeking for new methods to increase the recovery factor of oil fields. For that reason, many enhanced oil recovery (EOR) methods have been developed and applied in the field. EOR methods alter the physico-chemical conditions inside the reservoir. One possibility to achieve this is to inject an aqueous solution containing special chemicals into the oil-bearing zone. Polymers, for example, increase the viscosity of the injected water and hence improve the displacement of the oil to the production well. The injection of surfactant solutions results in reduced capillary forces, which retain the oil in the pores of the reservoir. Some surfactants form viscoelastic solutions under certain conditions. The possibil-ity to apply those solutions for enhanced oil recovery has been investigated by some authors in the last years in low salinity brines. Reservoir brines, however, often contain high salt concentrations, which have detrimental effects on the properties of many chemical solutions applied for EOR operations. The Triphenoxymethane derivatives, which were the subject of study in this thesis, form viscoelastic solutions even in highly saline brines. The aim of this thesis was to investigate the efficiency and the mode-of-action of this new class of chemical EOR molecules with respect to oil mobilization in porous media.

No description available.