Structure-Property Relationships of Graphene Nanoplatelets and their Functionalization to Enable Applications in Composites and Supercapacitors
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Authors
Haridas, Haritha
Date
2024-06-26
Type
thesis
Language
eng
Keyword
Graphene nanoplatelets , polymer , supercapacitors , composites , functionalization
Alternative Title
Abstract
This thesis establishes structure-property relationships of graphene nanoplatelets (GNPs), investigates applications in thermoplastic composites, and proposes a non-covalent functionalization method to enable applications in conductive films, supercapacitors and concrete reinforcement.
The first part of this thesis presents a fundamental investigation on the interfacial interactions between GNPs and the polymer matrix. The effect of specific surface area (SSA) on the rheological properties of a poly(ethylene oxide) matrix is studied under steady and small amplitude oscillatory shear. Hydrodynamic interactions governed rheological properties in composites containing less than 8 wt.% GNPs, while filler-filler interactions dominated at higher concentrations. Lower electrical and rheological percolation thresholds were achieved as the SSA of the GNPs increased. Rheological signatures, including the melt yield stress and two-phase model parameters, are identified allowing rheology to serve as a tool for the bulk characterization of GNPs.
The next section focuses on non-covalent functionalization to enhance GNP dispersion in solvents, polymers, and concrete. In the presence of trimellitic anhydride (TMA), the functionalized GNPs (TMA-GNPs) formed stable aqueous dispersions, while maintaining conductive properties. Supercapacitor electrodes with specific capacitance of 22.2 F/cm3 and 90% capacitance retention after 10,000 cycles were demonstrated. TMA-GNP addition enhanced the early-age compressive strength of concrete, with maximum mechanical property enhancements found at 0.15 wt.% of cement GNP content.
Enhanced dispersion of TMA-GNPs was achieved in poly(amide)6,12 (PA) matrix due to the compatibilization established through the interaction between the anhydride moiety and the amide groups in the GNPs and PA respectively. This yielded composites with higher crystallinity and functional properties, including enhanced dielectric permittivity. Flexural modulus of 6082 MPa, electrical conductivity of 0.23 S/m, thermal conductivity of 3.3 W/m.K was achieved for composites containing 40 wt.% GNPs, while 10 wt.% composites had twice the impact strength as neat PA. GNPs also improved the interface between recycled glass fibers and PA.
Poly(lactic acid) (PLA) composites containing GNPs and TMA-GNPs had similar properties, with maximum electrical conductivity of 0.2 S/m, and up to 142% and 105% increase in flexural modulus, respectively, compared to neat PLA. In the absence of specific interactions, GNPs remained in the form of multi-layered tactoids, with no additional benefits from TMA addition.
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Attribution 4.0 International
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.