Hybrid Structured Phenylethynyl Silsesquioxane Resin Composites

摘要

Thermosetting polyimides terminated with phenylethynly phthalic imides are thecurrent state-of-the-art high temperature resin for use in structural compositeapplications. However, due to the presence of imide group these resins often sufferhigh moisture uptake leading to property degradation during use. In addition, the needto remove condensation near the crosslinking reaction temperature as well as highglass transition temperature of unreacted oligomers, the processing window for thisclass of thermosetting is very narrow. Hence, the need to develop compounds with thesame terminating group with ease of processing is of significant interest. In this work,double-decker shaped silsesquioxane (DDSQ) terminated with multiple phenylethynylgroups was developed and curing process investigated. It was anticipated that DDSQas the backbone can provide the needed monodispersed characteristics in its molecularweight, while phenylethynyl groups form different isomers (region- and stereo-) aboutthe SiO core of DDSQ. This approach provides ease of processing while eliminatecrystallinity. In addition, the inorganic nature of these compounds also exhibited asignificant reduction in the moisture uptake which can greatly enhance in-serviceperformance of composites. Synthesis and purification of needed chlorosilanes and thesubsequence separation of these functionalized DDSQs by liquid chromatographywere performed without the need to use fractional crystallization as the firstpreparation step are presented. This approach greatly reduces the complexity andenables continuous process.