Date of Award

Spring 5-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

Committee Chair

Jeffrey S. Wiggins

Committee Chair Department

Polymers and High Performance Materials

Committee Member 2

Robson F. Storey

Committee Member 2 Department

Polymers and High Performance Materials

Committee Member 3

Sarah E. Morgan

Committee Member 3 Department

Polymers and High Performance Materials

Committee Member 4

Sergei I.Nazarenko

Committee Member 4 Department

Polymers and High Performance Materials

Committee Member 5

Joseph R. Lott

Committee Member 5 Department

Polymers and High Performance Materials

Abstract

This dissertation is focused on structure-property-processing relationship studies based on well-defined polyhedral oligomeric silsesquioxane (POSS) modified epoxy networks to present a comprehensive understanding of hybrid network behavior. In this research, a monoamine functional POSS molecule is incorporated into the epoxy monomer as pendant unit to mimic common epoxy structures and then crosslinked to form well-defined epoxy hybrid networks. The POSS cages behave as nanosized pendant unit in the epoxy matrices, while the mass fraction of POSS cages is varied and the effects on physical properties are examined with respect to changes in network architecture.

A novel continuous reactor method is developed to synthesize POSS-DGEBA precursor with the aim of improving prereaction efficiency between aminopropyl isobutyl POSS and DGEBA. Studies suggest that by using a continuous reactor, full conversion of aminopropyl isobutyl POSS into the precursor was achieved in less than a minute, compared to several hours in a batch process. Fabricating transparent networks with large mass fractions of pendant POSS by the continuous reactor method demonstrates the concept of network modification by molecular level dispersion of pendant POSS. Physical and thermal properties of hybrid networks demonstrate structure property relationships with respect to POSS content, which appears to be true network behavior, given that a molecular level dispersion of pendant POSS in crosslinked epoxy networks has been achieved.

Studies of nanostructured epoxy networks containing pendant POSS and non-functionalized silica nanoparticles (SNP) prepared using the continuous reactor method suggest that favorable interactions between pendant POSS and SNP surfaces enhance matrix nanoparticle interactions. Results suggest better dispersion of SNP and improved load bearing properties of these networks due to the favorable interaction between pendant POSS cage and SNP.

This research reveals a unique strategy for molecular level dispersion of pendant POSS into epoxy networks with excellent control over nanostructure formation and properties, leading to increased strength through plasticization of glassy polymer networks.

ORCID ID

0000-0002-9814-6432

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