Author: Yang Wang

Publisher:

Published: 2021

Total Pages:

ISBN-13:

Development of the next generation of high-performance polymer nanocomposites requires a detailed understanding of the underlying interfaces between constituents and their impact on the thermal and mechanical properties. In particular, the thermal conductivity and cohesive fracture resistance in nanocomposite materials is defined by the nature of interactions at the interface between the constituents. In my research, I have made advances in the performance of hyper-confined polymer nanocomposites using surface functionalization for fine-tuning the interfaces between molecularly confined polymers and the organosilicate glass matrix to improve the thermal and mechanical performance of these nanocomposites. Thermal reflectance and thin-film mechanics techniques were used to measure film thermal conductivity and mechanical properties of these nanocomposites. To correlate the improved thermal and mechanical properties, I used spectroscopic methods to quantify the chemical nature of the interface between functionalized porous organosilicate glass and organic polymers. A positive correlation is found between the extent of bonding at the interface as determined by infrared and X-ray photoelectron spectroscopies for multiple polymers and the resulting thermal and mechanical properties. Hyper-confined polyimide in porous organosilicate glass is a promising candidate for high temperature applications due to high fracture resistance and thermal stability. To characterize the nanocomposite performance, a thermal oxidative aging study was conducted and factors affecting the thermal stability of nanocomposite are analyzed. Using infra-red spectroscopy in addition to other techniques, I identified the key chemical and physical degradation pathways for the nanocomposite of polyimide and organosilicate glass at elevated temperatures. Surprisingly, the polyimide was found to be remarkably stable at > 300°C for over 200 hours in the nanocomposite, with the organosilicate glass being the limiting factor for thermal stability. Overall, I have developed an experimental framework combining chemical and mechanical methodologies to uncover the mechanisms governing the performance of hyper-confined polymer nanocomposites. These results will help further our understanding of the key structural and chemical factors governing the thermal and mechanical properties of nanocomposites.