Pohl, Svenja

► Research

Synthesis and characterization of reversibly meltable siloxane Hybrid Materials (Melting Gels)

The sol-gel process is a method to produce solids of different composition under mild conditions. Inorganic-organic hybrid materials provide a broad portfolio of applications in the fields of optics, electronics, and coatings by combining a wide range of functions in one material. Under conventional conditions, an insoluble, no longer processable material is produced at the end of the process. In the past, it has been shown that so-called melting gels can also be produced under controlled conditions with knowledge of the reactivity of the individual components.
These are siloxane-based hybrid materials that are hard at room temperature and melt reversibly at temperatures above 110°C. Hence, these materials show a thermoplastic behaviour. A consolidation process at higher temperatures leads to irreversible curing of these materials. The transparent glass-like polymers are produced from di- and/or trialkoxysilanes via a hydrolysis and condensation reaction. By varying the composition of the silane precursors, as well as the organic groups, properties such as the refractive index, hardness, and the melting and consolidation temperature can be changed. Due to their unique properties such as high transparency, high-temperature stability, and good resistance to discolouration, the hybrid gels show great potential in the field of optoelectronic encapsulation materials.
The PhD thesis investigates the molecular structure and the influence of different organic residues on the melting gel synthesis and the material properties. In this context, fluorine-containing melting gels with a low refractive index or aromatic materials with a high refractive index will be synthesised. The use of vinyl groups should lead to the possibility to post-functionalize the hybrid glasses. The aim is to create application-oriented hybrid materials with various adjustable properties by varying the organic residues.