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Synthese und Selbstassemblierung von schaltbaren Kern-Schale Janus Partikel

Fachliche Zuordnung Präparative und Physikalische Chemie von Polymeren
Polymermaterialien
Förderung Förderung von 2014 bis 2020
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 251031172
 
Erstellungsjahr 2020

Zusammenfassung der Projektergebnisse

In summary, a flexible route for the fabrication of diverse types of spherical hybrid hairy Janus particles with easily tunable Janus ratio and chemical functionalities has been developed. In order to measure the contact angle of Janus particles directly and in situ at a water-oil interface, a new methodology, FreSCa cryo-SEM, has been employed and revealed that the amphiphilic behavior of Janus particles at an interface is related to the Janus ratio and the wettability contrast between the two portions of the surface. Furthermore, we have developed a novel approach for the large-scale synthesis of hybrid platelet-like Janus particles with hairy polymer shells based on the fabrication of an emulsion consisting of water and oil solutions of hydrophilic and hydrophobic monomers stabilized by initiator-modified kaolinite particles. The advantage of this approach is its simplicity and the possibility of the synthesis of large amounts of Janus particles at once – up to several grams in a single batch, which is one of the main challenges in the synthesis of Janus particles in general. The proposed approach can be applied to various surfaces with disc-like or platelet-like geometry, and hence can aid in the design of advanced functional materials for different technological applications such as stabilization of emulsions, and ultimately the design of anti-icing or anti-fouling coatings. Secondly, the assembly behavior of homogeneously decorated and Janus particles in dispersion has been compared. Homogeneously decorated particles of one sort formed aggregates under conditions where the polymer chains are collapsed or not soluble. In contrast, hairy Janus particles formed ordered chain-like structures with different thicknesses in water and organic solvents. The ordered structure formation indicates on the unique features of the Janus particle assembly compared to homogeneous particles and opens new paths into the programmed development of specifically designed materials. Moreover, an easy and adjustable bottom-up approach for the programmed assembly of binary mixtures of oppositely charged homogeneous and Janus particles was demonstrated. Electrostatic interactions between the particles were mediated by grafted polyelectrolytes on their surface, which also introduced pH-responsive properties to the system. We designed two different assembly routes depending on the target structures: half-raspberry-like or cluster-/chain-like structures. Stable asymmetric micro-structures could be obtained in a wellcontrolled manner in dry and dispersed state. The particle size ratio and the mass ratio strongly determined the geometry of the obtained constructs. The assembled structures could be disassembled on demand by changing the pH value and then reassembled many times. The obtained results point out a further step towards the tailored synthesis of multifunctional patchy and Janus particles. Furthermore, the spatially separated functionalities of the asymmetric Janus particle-based micro-clusters allow their programmable and reversible assembly into complex hierarchical constructs, which may open up a variety of selfassembly-based applications towards miniaturization of machines, catalysis, photonics/plasmonics, photovoltaics, and nanoscale electronics.

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