Diblock copolymer based self-assembled nanomagnetoelectric

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/apl/93/17/10.1063/1.3005558.A magnetoelectric (ME) composite with controlled nanostructures is synthesized using coassembly of two inorganic precursors with a block copolymer. This solution processed material consists of hexagonally arranged ferromagnetic cobalt ferrite [CoFe2O4 (CFO)] nano cylinders within a matrix of ferroelectric lead zirconium titanate [Pb1.1(Zr(0.53)Ti(0.47))O3(PZT)] when thin films were prepared by spin coating. The initial magnetic permeability of the self-assembled CFO/PZT nanocomposite changes by a factor of 5 through the application of 2.5V. This work also demonstrates that a block copolymer can be used to simultaneously template two compound inorganic phases to form a nanoscale composite

Second kind integral equations on the real line : solvability and numerical analysis in weighted spaces

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Anisotrope Kolloide aus flüssigkristallinen Polymeren

In dieser Arbeit wurden Kolloide aus flüssigkristallinen Polymeren dargestellt und untersucht.rnrnDie Methode der Dispersionspolymerisation zur Darstellung von Kolloiden aus flüssigkristallinen Polyacrylaten wurde in unpolare Lösungsmittel adaptiert, umrneine Manipulierbarkeit anisotroper Kolloide durch elektrische Felder zu erreichen.rnDazu wurden ein Gemisch aus THF und Siliconöl als Reaktionsmischung gewähltrnund polysiloxanbasierte Polymere und Copolymere als Stabilisatoren eingesetzt.rnDabei auftretende unerwartete Auswirkungen auf die Mesogenkonfiguration führtenrnzu einer Untersuchung der Abhängigkeit der Mesogenkonfigurationen von der Oberflächenverankerung der Mesogene. Schließlich wurde eine Kontrolle derrnOberfl¨achenverankerung der Mesogene und somit eine Kontrolle der Mesogenkonfigurationen unter Ausnutzung der Eigenschaften flüssigkristallin/nicht flüssigkristalliner Blockcopolymere erreicht. Zu diesem Zweck wurde auch ein neuer Makroinitiator entwickelt. Kleine Kolloide konnten mittels eines elektrischen Feldes gedreht bzw. zu Linien angeordnet werden.rnrnEinige neue Polysiloxane wurden zum Einbau in flüssigkristalline Kolloide viarnMiniemulsion synthetisiert. Sie wurden charakterisiert und in Kolloide überführt. Aufgrund zu hoher Übergangstemperaturen konnten bei den meisten jedoch keine Strukturen aus phasenseparierten Polysiloxane gefunden werden. Die Ausbildung der Strukturen in solchen Kolloiden konnte aber trotzdem verstanden werden.rnrnAus vernetzten Hauptkettenpolymeren sollten aktuierende Kolloide hergestelltrnwerden. Dazu wurde das entsprechende Hauptkettenpolymer hergestellt, charakterisiert und per Miniemulsion in Kolloide überführt. Die dargestellten Kolloide wurden unter dem TEM geheizt und zeigten Formänderungen, die jedoch nicht kontrolliert und noch irreversibel waren.In this work, colloids from liquid crystalline polymers were synthesized and characterized.rnrnThe dispersion polymerization method for the synthesis of colloids from LC polymers was modified for the use of nonpolar solvents to achieve manipulation of such colloids in electric fields. rnFor this, a mixture of THF and silicone oil was employed as reaction mixture and polysiloxane based polymers and copolymers were used as stabilizers. Resulting unexpected effects on the mesogen configuration in such colloids led to the investigation of the influence of mesogen surface anchoring on the mesogen configuration. Control over the surface anchoring was achieved by employing self-organization phenomena in LC/non-LC block copolymers systems. A new macroinitiator was developed and colloids could be manipulated in electric fields.rnrnSome new polysiloxanes were syntesized for the incorporation in LC collods. They were characterized and colloids from them were prepared using the miniemulsion process. Very high transition temperatures prevented phase separation in the colloids, nevertheless the structure formation in such colloids could be understood.rnrnThe road to actuating colloids was investigated by the syntesis of colloids from crosslinked main-chain polymers. The polymers were synthesized and characterized and turned into colloids via the miniemulsion process. Heating under a TEM showed shape change, though it was uncontrolled and not yet reversible

Control of mesogen configuration in colloids of liquid crystalline polymers

We report on a method to chemically predetermine the surface anchoring of mesogens in liquid crystalline colloids formed by different types of dispersion polymerization, and hence to achieve control over the mesogen configuration in such colloids. The surface anchoring is controlled by the chemical linkage of the polymers forming the colloids to the surfactants stabilizing the colloids towards the dispergent. We find that the hydroxypropyl cellulose used in conventional dispersion poylmerization induces parallel mesogen surface anchoring that in turn leads to bipolar director-field configurations, while a methacrylate terminated polysiloxane stabilizer, which is used in nonpolar dispersion polymerization, induces perpendicular anchoring and because of that to radial or axial configurations, depending on the size of the synthesized colloid. These differences in surface anchoring tendencies are due to differences in the molecular structure of the LC/non-LC block copolymers formed by the mesogens and the stabilizers. Based on these observations we synthesized a novel macroinitiator able to induce bipolar director-field configurations in the nonpolar dispersion polymerization