Schichtsilicate als effiziente Bausteine für funktionelle Nanokomposite

A concept for the progressive generation of efficient polymer layered silicate nano-composites is described within this thesis. These nanocomposites require the optimization of four crucial factors, the aspect ratio and the mechanical properties of the nanofiller, as well as its compatibilization with and texturizing within the polymer matrix. Firstly, an important issue was the synthesis of a highly pure, coarse-grained layered silicate that fulfilled the requirements as nanofiller. A combination of melt synthesis followed by long-term annealing provided a unique material showing unprecedented activation with respect to intracrystalline reactivity. Due to annealing huge particle sizes in the range of 20 µm and high material purity could be obtained. In a mild anisotropic top down process the aspect ratio of this layered silicate could be maximized via delamination caused by os-motic swelling. Hereby aspect ratios of about 20000 were realized. In combination with fur-ther outstanding physical properties like homogeneous charge density and high optical transparency that material offered an ideal platform as filler for sophisticated nanocompo-sites in the in the field of sensitive optoelectronics packaging. A further central aspect of this work was the mechanical characterization of single nano-platelets for their application in nanocomposites. Two AFM-based methods were developed enabling the analysis of monolayers up to platelets of about 80 nm thickness. A nanoscale bending test offered new insights into the bending stiffness of clay platelets that are suitable for extrusion-based composites. For applications in nanocomposite coatings the mechanical performance of a single clay lamella was of crucial importance. Via a controlled wrinkling process on a deformable polymeric substrate the in-plane modulus of singular layered sili-cate lamellae could be extracted very efficiently. Because of the efficiency and high resolution of the wrinkling metrology the in-plane moduli of inhomogeneous graphene oxide and chemically derived graphene could be obtained with sub-micron spatial resolution. Comparison with chemical vapor deposited graphene revealed the real capability of such materials implemented as fillers in nanocomposites. Furthermore, the wrinkling method could be applied to discern quickly and unambiguously between mon-olayer and bilayer graphene. With a simple but efficient organophilization of the silicate lamellae described above a time-saving phase transfer into an organic solvent and an interface-optimized compounding with commercially available polyurethane precursor polymers could be achieved. In a subsequent bottom up process these nanoscale building blocks could be oriented on the mesoscale ap-plying a cost-effective texturizing process yielding a nanocomposite coating with ultra-high gas barrier. Extremely low oxygen transmission rates, high transparency and flexibility ena-ble an application for efficient packaging of sensitive and flexible OLEDs. Furthermore, due to the high charge homogeneity of the synthesized layered silicate transi-tion metal complexes could be oriented on its interfaces yielding polarized emission. That novel approach could be applied to synthesize efficient, polarized, flexible and at the same time resistant nanocomposite OLEDs.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bayreuth

Year

2013

Author dc:creator

• Kunz, Daniel

Contributors dc:contributor

• Breu, Josef

Repository record source_url

https://epub.uni-bayreuth.de/id/eprint/56/

OAI identifier oai:identifier

oai:epub.uni-bayreuth.de:56