Polymere sind lange kettenartige Moleküle. Sie bestehen aus vielen elementaren chemischen Einheiten, den Monomeren, die durch kovalente Bindungen aneinander gekettet sind. Polyelektrolyte sind Polymere, die ionisierbare Monomeren enthalten. Aufgrund ihrer speziellen Eigenschaften sind Polyelektrolyte sowohl in der Molekular- und Zellbiologie von großen Bedeutung als auch in der Chemie großtechnisch relevant. <br /> Verglichen mit ungeladenen Polymeren sind Polyelektrolyte theoretisch noch wenig verstanden. Insbesondere gilt dies für Polyelektrolyte in sogenanntem schlechten Lösungsmittel. Ein schlechtes Lösungsmittel bewirkt eine effektive Anziehung zwischen den Monomeren. Für Polyelektrolyte in schlechtem Lösungsmittel kommt es daher zu einer Konkurrenz zwischen dieser Anziehung und der elektrostatischen Abstoßung. <br /> Geladene Polymere werden im Rahmen der chemischen Klassifikation in starke und schwache Polyelektrolyte unterschieden. Erstere zeigen vollständige Dissoziation unabhängig vom pH-Wert der Lösung. Die Position der Ladungen auf der Kette wird ausschließlich während der Polymersynthese festgelegt. In der Physik spricht man deshalb von Polyelektrolyten mit eingefrorener Ladungsverteilung (quenched polyelectrolytes). <br /> Im Falle von schwachen Polyelektrolyten ist die Ladungsdichte auf der Kette nicht konstant, sondern wird durch der pH-Wert der Lösung kontrolliert. Durch Rekombinations- und Dissoziationsprozesse sind die Ladungen auf der Kette beweglich. Im allgemeinen stellt sich eine inhomogene Gleichgewichtsverteilung ein, die mit der Struktur der Kette gekoppelt ist. Diese Polymere werden deshalb auch Polyelektrolyte mit Gleichgewichtsladungsverteilung (annealed polyelectrolytes) genannt. Wegen des zusätzlichen Freiheitsgrades in der Ladungsverteilung werden eine Reihe ungewöhnlicher Eigenschaften theoretisch vorhergesagt. <br /> Mit Hilfe von Simulationen ist es zum ersten Mal gelungen, zu zeigen daß 'annealed' Polyelektrolyte in relativ schlechtem Lösungsmittel einen diskontinuierlichen Phasenübergang durchlaufen, wenn ein kritischer pH-Werts der Lösung überschritten wird. Bei diesem Phasenübergang, gehen die Polyelektolyte von einer schwach geladenen kompakten globulären Struktur zu einer stark geladenen gestreckten Konfiguration über. <br /> Aufgrund theoretischer Vorhersagen wird erwartet, daß die globuläre Struktur in weniger schlechtem Lösungsmittel instabil wird und sich eine Perlenkettenkonfiguration ausbildet. Diese Vorhersage konnte für 'annealed' Polyelektrolyte mit den durchgeführten Simulationen zum ersten Mal bestätigt werden - inzwischen auch durch erste experimentelle Ergebnisse. <br /> Schließlich zeigen die Simulationen auch, daß annealed Polyelektrolyte bei einer kritischen Salzkonzentration in der Lösung einen scharfen Übergang zwischen einem stark geladenen gestreckten Zustand und einem schwach geladenen globulären Zustand aufweisen, wiederum in Übereinstimmung mit theoretischen Erwartungen. / A polymer is a large molecule made up of many elementary chemical units, joined together by covalent bonds (for example, polyethylene). Polyelectrolytes (PELs) are polymer chains containing a certain amount of ionizable monomers. With their specific properties PELs acquire big importance in molecular and cell biology as well as in technology.<br /> Compared to neutral polymers the theory of PELs is less understood. In particular, this is valid for PELs in poor solvents. A poor solvent environment causes an effective attraction between monomers. Hence, for PELs in a poor solvent, there occurs a competition between attraction and repulsion.<br /> Strong or quenched PELs are completely dissociated at any accessible pH. The position of charges along the chain is fixed by chemical synthesis. On the other hand, in weak or annealed PELs dissociation of charges depends on solution pH.<br /> For the first time the simulation results have given direct evidence that at rather poor solvents an annealed PEL indeed undergoes a first-order phase transition when the chemical potential (solution pH) reaches at a certain value. The discontinuous transition occurs between a weakly charged compact globular structure and a strongly charged stretched configuration.<br /> At not too poor solvents theory predicts that globule would become unstable with respect to the formation of pearl-necklaces. The results show that pearl-necklaces exist in annealed PELs indeed.<br /> Furthermore, as predicted by theory, the simulation results have shown that annealed PELs display a sharp transition from a highly charged stretched state to a weakly charged globule at a critical salt concentration.

In printed electronics there are many polyelectrolytes to choose from. While polyelectrolytes such as polystyrene sulfonic acid can fulfill many ofthe desired functionalities of a semiconductor, there is a need for other polyelectrolytes with other functionalities, such as functionality at low airhumidity and better cross-linking possibilities, while still functioning as a good semiconductor.Within this thesis, there is a description of general polyelectrolytes, as well as various usages.The synthesis and characterization of new polyelectrolytes that have been developed, based upon diallyldimethyl ammonium chloride (DADMAC)and a derivative of polystyrene sulfonic acid (PSSH) is described.The study and experimental testing of the polymers as polyelectrolytes under different conditions is described.

No description available.

<p>Microcontact printing using elastomeric stamps is a technique used in finding new and efficient ways to produce biodetection chips. Microcontact printed, with poly(dimetylslioxane) (PDMS) stamps, patterns of antibodies have been evaluated using fluorescence microscopy, imaging ellipsometry and atomic force microscopy. Fluorescent conjugated polyelectrolytes form non-covalent molecular complexes with Immunoglobulin-γ type antibodies, antigen binding to the tagged antibody result in spectroscopic shifts. Four different conjugated polyelectrolytes (POWT, POMT, PTT, PTAA) in complex with human serum albumin antibodies (aHSA) have been tested with fluorescence spectroscopy. Complexes of POWT and aHSA gave rise to thelargest wavelength shift when exposed to human serum albumin.</p><p>Several types of commercially available fluorescent antibodies and antigens were used to test the specificity of microcontact printed antibodies to different antigen solutions. Using fluorescence microscopy it could not be shown that printed antibody patterns promote specific adsorption of corresponding antigen. It is proposed however that changed surface characteristics of the substrate due to PDMS residues transferred during printing is the main driving force behind antigen adsorption.</p><p>POMT - poly (3-[(s)-5-amino-5-methoxylcarboxyl-3-oxapentyl]-2,5-thiophenylenehydrochloride)</p><p>POWT - poly (3-(s)-5-amino-5-carboxyl-3-oxapentyl]-2,5-thiophenylenehydrochloride)</p><p>PTAA - polytiophene acetic acid</p><p>PTT - poly (3-[2,5,8-trioxanonyl] thiophene)</p>

Thesis (Ph. D.)--Institute of Paper Chemistry, 1978. / Bibliography: leaves 156-165.

No description available.

Microcontact printing using elastomeric stamps is a technique used in finding new and efficient ways to produce biodetection chips. Microcontact printed, with poly(dimetylslioxane) (PDMS) stamps, patterns of antibodies have been evaluated using fluorescence microscopy, imaging ellipsometry and atomic force microscopy. Fluorescent conjugated polyelectrolytes form non-covalent molecular complexes with Immunoglobulin-γ type antibodies, antigen binding to the tagged antibody result in spectroscopic shifts. Four different conjugated polyelectrolytes (POWT, POMT, PTT, PTAA) in complex with human serum albumin antibodies (aHSA) have been tested with fluorescence spectroscopy. Complexes of POWT and aHSA gave rise to thelargest wavelength shift when exposed to human serum albumin. Several types of commercially available fluorescent antibodies and antigens were used to test the specificity of microcontact printed antibodies to different antigen solutions. Using fluorescence microscopy it could not be shown that printed antibody patterns promote specific adsorption of corresponding antigen. It is proposed however that changed surface characteristics of the substrate due to PDMS residues transferred during printing is the main driving force behind antigen adsorption. POMT - poly (3-[(s)-5-amino-5-methoxylcarboxyl-3-oxapentyl]-2,5-thiophenylenehydrochloride) POWT - poly (3-(s)-5-amino-5-carboxyl-3-oxapentyl]-2,5-thiophenylenehydrochloride) PTAA - polytiophene acetic acid PTT - poly (3-[2,5,8-trioxanonyl] thiophene)

Polyelectrolytes coated on high surface curvature nanoparticles (NPs) have been prepared and characterized by a variety of solid-state nuclear magnetic resonance (NMR) experiments in order to examine surface interactions, polymer-water association and polymer dynamic properties of layer components. Gold nanoparticles of four nanometers in diameter pre-stabilized by 4-dimethylaminopyridine (DMAP), and silica and neodymium NPs were chosen as substrates for these studies. The high surface to volume ratio provided by such nanoparticles is advantageous for NMR analysis, which requires a high material content for adequate sensitivity. Firstly, poly(styrene sulfonate) was deposited on gold NPs by electrostatic self-assembly where charged polyelectrolytes adsorb onto an oppositely charged substrate. Surface charges on gold NPs were provided by the ligand DMAP that induces a positive charge at the NP surface that is otherwise neutral. Nanoparticle encapsulation by PSS was monitored by the gold surface plasmon absorption band (SPB) which revealed a good stability under assembly conditions where the pH was maintained above the DMAPsoln pKa and for a polymer radius of gyration comparable to the particle radius. An electrostatic association between DMAPbound and PSS, rather than a ligand substitution, was detected by solid state 13C NMR. When a subsequent layer composed of a weak or a strong polycation was added, the stability of the bilayer was found to be dictated by the nature of the multiple, weak interactions of the polymer functional groups (SO3, NH2, N(CH 3)2+Cl-, NH3 +) with the gold surface relative to that of DMAPbound which in turn is influenced by the assembly pH. / A detailed study of the interactions between the polyelectrolytes, stabilizers and substrates was also extended to polyelectrolyte multilayers coated on gold NPs of different dimensions. Limitations in the application of the layer-by-layer self-assembly technique to very small NPs were investigated and strategies to optimize the method were proposed. 1H NMR analysis in the solid state and 2H NMR analysis in solution revealed that water association and film dynamics were closely related to the identity of the capping layer and independent of even/odd layer effects. These results were compared to those obtained for larger NP substrates which revealed many similarities between the two systems. / A study of the parameters that affect the fabrication of Poly(L-lysine) and DNA polyelectrolyte multilayer films was also conducted for both flat and highly curved surfaces. Such polyelectrolyte films coated on nanopartic1es can be considered as potential vectors for gene therapy. Control over DNA loading into films was performed by varying the ionic strength and pH of polyelectrolyte assembly solutions. DNA density, film degradability and transfection efficiency were examined to determine optimal conditions for vector preparation in gene therapy. Finally, the acid-base properties of lanthanide-based nanoparticles of 10 nm of diameter were explored under a wide range of pH conditions. The interactions of the neodymium oxide nanoparticles with the cationic poly(allylamine hydrochloride) and the anionic poly(styrene sulfonate) polymers were investigated by following spectroscopically optical changes in suspension absorbance and visual changes in NP dimensions. Transparancy and efficiency of stabilization were the evaluated criteria for polymers to be considered as potential stabilizing agents for neodymium oxide NPs used in neutrino detection experiments.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007. / Committee Chair: Wong, C.P.; Committee Co-Chair: Liu, Meilin; Committee Member: Barefield, Kent; Committee Member: Collard, David; Committee Member: Fahrni, Christoph.

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2005. / Niren Murthy, Committee Member ; Andrš J. Garca̕, Committee Member ; Joseph M. Le Doux, Committee Chair ; Mark R. Prausnitz, Committee Member ; H. Trent Spencer, Committee Member. Includes bibliographical references.