Date of Award

Fall 2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

Committee Chair

Dr. Jeffrey S. Wiggins

Committee Chair Department

Polymers and High Performance Materials

Committee Member 2

Dr. Robson F. Storey

Committee Member 2 Department

Polymers and High Performance Materials

Committee Member 3

Dr. Derek L. Patton

Committee Member 3 Department

Polymers and High Performance Materials

Committee Member 4

Dr. William L. Jarrett

Committee Member 4 Department

Polymers and High Performance Materials

Committee Member 5

Dr. Gopinath Subramanian

Committee Member 5 Department

Polymers and High Performance Materials

Abstract

Despite the modularity in molecular design and high-performance properties of benzoxazine thermoset chemistries, there are two primary shortcomings of benzoxazine marketability. Firstly, multifunctional benzoxazines are unfavorable for processing as they are glassy solids at ambient temperature. Secondly, benzoxazine chemistries are commercially synthesized using batch reactors, which are energy intensive and require the use of environmentally unfavorable solvents.

The purpose of the work herein is to address these shortcomings, which include:

1.) interrelationships between molecular architectures of synthesized monofunctional benzoxazine monomers and their ambient temperature physical states (i.e. liquid or solid) using molecular dynamics simulations and experimental comparisons,

2.) continuous high-shear reactor designs to synthesize high-purity benzoxazine monomers and prepolymers, and

3.) correlations between the molecular architecture and percent loading of fluorinated monofunctional benzoxazine reactive diluent isomers on the thermal and bulk mechanical properties of BPABOX networks.

In Chapters I and II, research motives and all experimental and characterization methods are provided.

Chapter III of this work involved synthesizing and simulating a library of monofunctional benzoxazine monomers varied by substituent placement and identity. Annealing simulations demonstrated a discontinuity that provided a qualitative prediction of the physical state of benzoxazine monomers. Ab initio calculations demonstrated that electron rich domains align with electron poor domains providing localized order within a monomeric system and a solid physical state.

In Chapter IV, a novel continuous high-shear reactor design, CHSR, for the synthesis of benzoxazine monomers and prepolymers is provided. Validated by 1H NMR, the CHSR demonstrated throughputs that are 6-40x faster with improved target monomer conformation as compared to current reactor technologies. Proton NMR comparisons of monomers synthesized and purified from a batch reactor versus unpurified monomers from the CHSR demonstrated that the CHSR yields a high purity product eliminating the need for post-processing purification.

Chapter V of this work involved the preparation of benzoxazine alloys to elucidate the effects of molecular architecture and percent loading of fluorinated reactive diluent isomers on the BPABOX bulk matrix properties. Contrastingly, 49 wt.% of diluent was determined as the critical loading for an isomer effect on the cured network properties. Despite the increasing molecular weight between crosslinks with increasing diluent loading, plasticization was prevented up to 30 wt.% diluent. The added fluorine content afforded increased secondary interactions that could provide added energy dissipation modes to toughen the inherently brittle neat BPABOX network as demonstrated via dynamic mechanical analyses and uniaxial compression results.

ORCID ID

orcid.org/0000-0002-4583-3132

Available for download on Sunday, December 08, 2019

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