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Title: Innovative routes to carbon nanotube composites
Author: Clancy, Adam Richard Justin
ISNI:       0000 0004 6495 6044
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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Single-walled carbon nanotubes (SWCNTs) have superlative properties, but applications which can exploit these on a macroscopic scale have been hindered due to damage from processing, impurities, heterogeneity, and agglomeration. The creation of reduced nanotubes (nanotubide) allows SWCNTs to dissolve as individualised species using Columbic repulsion in a non-damaging manner. The synthesis of nanotubide solutions is accelerated through the use of sodium naphthalide in dimethylacetamide, which simultaneously reduces and dissolves SWCNTs. The system creates high concentration solutions and can be modified to facilitate efficient, mild, kinetically driven purification. Nanotubide undergoes reductive functionalisation and reaction variables were investigated to increase grafting density, including charging stoichiometry, nanotube concentration, reagent sterics, SWCNT purity and anionic leaving group. An intermediate sodium concentration (25 mM) is necessary to balance insufficient charge at low concentrations and counterion condensation at high concentrations. Functionalisation of nanotubide with oligomeric species terminated with bulky aryl groups allows individualised SWCNTs to remain in solution after the functionalisation. Coagulation fibre spinning of SWCNT composites requires high concentrations and well dispersed species, making nanotubide an ideal candidate. By coagulating nanotubide into poly(vinyl chloride) the reactivity of nanotubide was utilised, forming a cross-linked composite. Altering the SWCNT source, polymer molecular weight and coagulant concentration led to strain hardening composite fibres with strengths up to 482 MPa. Alternatively, poly(vinyl acetate) (PVAc) can be used to form fibres that can be deprotected to form poly(vinyl alcohol) composites. The dispersion of nanotubes can be improved through functionalisation of SWCNTs, although the final fibre mechanical properties are dominated by the fibre macrostructure. Notwithstanding, nanotubide has been shown to be a versatile route to novel hierarchy composites and has potential for many other applications.
Supervisor: Shaffer, Milo Sponsor: Engineering and Physical Sciences Research Council ; Thomas Swan Ltd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral