Date of Award
5-2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
School
Polymer Science and Engineering
Committee Chair
Jeffery Wiggins
Committee Chair School
Polymer Science and Engineering
Committee Member 2
James Rawlins
Committee Member 2 School
Polymer Science and Engineering
Committee Member 3
Sergei Nazarenko
Committee Member 3 School
Polymer Science and Engineering
Committee Member 4
Zhe Qiang
Committee Member 4 School
Polymer Science and Engineering
Committee Member 5
Olivia McNair
Committee Member 5 School
Polymer Science and Engineering
Abstract
The development of high temperature matrices most suitable for thermal protection systems often requires highly aromatic thermoset monomers with exceptional thermal performance in harsh environments. This structural requirement, however, typically creates a challenging processing-property balance that needs to be addressed for adequate composite manufacturability and thermal performance. Herein, it was demonstrated that well established synthetic methodologies could be utilized to rationally design processable, high char yielding bismaleimide structures. Chapter III details the functionalization of bismaleimide monomers with acetylene and nitrile moieties. Through various polymerization and mass spectroscopy characterization techniques, the effects of the aforementioned functionalities on the decomposition pathway of bismaleimide-based networks are revealed. The acetylene terminated bismaleimide (A-BMI) was observed to yield the highest mass retentions by both the mitigation of the primary stage of bismaleimide decomposition and the retention of aromatic structures during pyrolysis. Chapter IV builds upon these synthetic strategies, where acetylene functional comonomers were blended with A-BMI to afford processable, bismaleimide-based carbon precursors. Within these comonomer blends, comonomer isomerism was used to tailor rheological profiles and polymerization efficacies through use of a meta and para substituted acetylene. It was revealed that the meta substitution granted lower minimum viscosities and higher functional group consumption, while the para substitution yielded earlier onset of polymerization and higher viscosities. The comonomers’ influence was further observed through various structural analysis of network formation within Chapter IV and decomposition analysis techniques within Chapter V, where optimal cure temperatures could be utilized to produce high char yields (>50%) at high comonomer concentrations. The comonomers were found to increase iii A-BMI’s initial stages of decomposition and yield the monotonic evolution of chain scission products. This was observed to be consistent with the kinetic analysis of decomposition, where the comonomers were concluded to lower activation energy for chain scission during these initial stages. Within Chapter VI, the comonomers’ enhancement of A-BMI’s processability was exploited to incorporate a metallocene additive to afford the creation of inorganic-organic hybrid polymer networks and carbon morphologies. Higher comonomer concentrations correlated with increased homogenization of the inorganic additive during monomer processing. Ferrocene, the chosen metallocene, was found to participate in the network formation of the comonomer blends. This led to accelerated decomposition events with the additive’s covalent attachment within the polymer network. Despite this, ferrocene was found to significantly improve both the carbon microstructure and morphology, leading to drastic improvements in both the graphitic crystallite dimensions and graphitic carbon content, respectively. Chapter VII down-selects and performs the fabrication of a half-inch thick carbon fiber reinforced composite panel. Typically, solvent based methods are utilized for processing acetylene functional resins. This chapter highlights the versatility of composite processing through the use of preform fabrication via solid loading of the down-selected resin. Analysis of the cured composite panel revealed that the resin achieved proper fiber impregnation, with the presence of void content located only in the upper corners of the panel. Small degrees of void content were found throughout the core of the panel and was in line with the microporous nature of acetylene-based polymers. This was observed to lower the interlaminar strength of the composite panel.
Copyright
David C. Walker, 2026
Recommended Citation
Walker, David C., "The Influences of Acetylene and Nitrile Functionalities on The Pyrolysis Behavior of Bismaleimide Matrices" (2026). Dissertations. 2463.
https://aquila.usm.edu/dissertations/2463