Date of Award

Spring 2020

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Polymer Science and Engineering

Committee Chair

Dr. Yoan Simon

Committee Chair School

Polymer Science and Engineering

Committee Member 2

Dr. Sergei Nazarenko

Committee Member 2 School

Polymer Science and Engineering

Committee Member 3

Dr. Xiaodan Gu

Committee Member 3 School

Polymer Science and Engineering

Abstract

Fillers are used ubiquitously throughout the fields of polymer and material science to overcome many inherent limitations to polymeric materials (i.e. poor stiffness or strength) and to expand their potential applications. There is a need to develop controllable particle architectures to better understand fundamental structure-property relationships in particle reinforced polymer composites. Charge-transfer complexes (CTCs) can assemble in situ into various needle and dendritic shapes via simple fabrication processes and at low loading levels. In this study, the effect of tetrathiafulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) CTC crystallites of various shapes and sizes on composite mechanical properties was investigated in an LDPE (low density polyethylene) polymer matrix. The CTC morphology was selectively controlled via the concentration, compression-molding temperature, or cooling rate to form needle and highly branched dendritic micro-crystallites. Optical imaging was used visualize the microstructure of the CTC crystallites. Fourier-transform infrared spectroscopy (FTIR) was used to confirm complexation of the TTF-TCNQ via shifts in the aromatic C-H and nitrile stretches in the composite samples. Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD) results show that the presence of the CTC inclusions does not affect LDPE crystallization. In general, there was no observed difference between in the modulus, yield stress, and ultimate tensile strength between controls and the composite samples cooled at their corresponding rates. However, the elongation at break for the dendritic composites appeared to decrease as a function of dendrite size. Interestingly in some cases, the mechanical properties had a slight dependence on the CTC concentration and not particle morphology.

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