Date of Award

Fall 12-11-2015

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

James W. Rawlins

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. Sarah E. Morgan

Committee Member 4 Department

Polymers and High Performance Materials

Committee Member 5

Dr. Robson F. Storey

Committee Member 5 Department

Polymers and High Performance Materials

Abstract

In this dissertation, relationships between chemical structures, cure kinetics and network architectures are correlated to bulk mechanical properties for novel, hybrid epoxy-amine networks. The work is split into two primary sections: the first is the synthesis and characterization of multifunctional glassy networks based on aryl-ether-ketone diamine curatives, while the second is based on the synthesis and characterization of hyperbranched epoxy polymers and their resulting networks.

Three aryl-ether-ketone (AEK) diamines of increasing molecular weights were synthesized and used to cure 4,4’-tetraglycidylether of diaminodiphenylmethane (TGDDM); the resulting networks were compared to 4,4’-diaminodiphenyl sulfone cured TGDDM. Architectural differences were created by varying cure profiles, and characteristics such as sub-Tg motions and free volume were altered to study bulk properties such as thermal stability, glass transition, mechanical properties, and moisture resistance. Additional analysis coupled molecular dynamics simulations and free volume data to relate AEK molecular-level characteristics to bulk properties. Simulation showed that enhanced chain packing and conformational freedom provided networks with similar hole free volume characteristics but created increased fractional free volume with increase in Mc. Activation energies of the two sub-Tg relaxations correlated with the free volume findings. Conformational freedom was also related to mechanical properties, which was related to enhanced secondary interactions.

Additionally, AEK diamines were copolymerized with DDS to form blended, hybrid networks with TGDDM. Blended networks offered further insight into the effects of chemical composition and Mc effects by varying AEK concentration. It was found that low concentrations of AEK-diamines could significantly alter DDS-cured networks.

The second section of this work involved the blending of an epoxide-functional hyperbranched polymer (HBE) into a glassy epoxy network. It was found that the network-level incorporation and high concentration of secondary interactions allowed simultaneous improvements in modulus and toughness. Further thermal and mechanical improvements were found by incorporation of POSS-units onto the hyperbranched polymer. The bulk property improvements were found to correlate with the multiscale dispersion of POSS. Finally, POSS-HBE carbon-fiber composites were fabricated and tested. Composite properties were related to those of the matrix material.

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