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Title: Models of technological polymers
Author: Molinari, Nicola
ISNI:       0000 0004 7658 2035
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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Polymers are widely adopted in many industrial sectors, where they usually constitute small but crucial technological components. In the oil and gas industry, polymer seals should act as impermeable barriers to protect sophisticated downhole equipment from corrosion. Additionally, their mechanical properties play an important role in communicating information from the bottom of the well to the surface. However, costly permeation-driven failures are observed. In the energy storage sector, polymers are promising candidates for safer electrolytes that do not suffer from safety issues related to leakage, shorting and combustible reactions. However, cation mobility in polymer-based electrolytes must be improved to attain commercial viability. Finally, nanoparticles have been recently suggested as universal and inexpensive polymer adhesives, possibly solving the century-old problem of adhering soft matter together. The common thread is that significant insight can be gained through a molecular-level understanding of the underlying mechanisms. Using a molecular-simulation-based approach, I have investigated the trends in, and the fundamental drivers of, the properties of these three technology-relevant polymer systems. In the oil and gas industry, hydrogenated nitrile butadiene rubber is widely adopted, and I have developed and validated a molecular model for it based on the OPLS-AA force-field. I have also studied the mechanical properties of filled elastomers using a coarse-grained model, and have uncovered important connections between filler loading, polymer-fillers network, and the stress-strain response of the material. In battery technology, poly(ethylene)oxide/Li/bis(trifluoromethane)sulfonimide is a promising electrolyte system, and I have demonstrated the central role of the anion in coordinating lithium atoms and the appearance of asymmetrical cation/anion clusters. Finally, I have investigated the use of nanoparticles as universal glue by studying the effects on the stress-strain response of nanoparticles' size, nanoparticle-polymer interaction strength and density. The latter influences the organisation of the nanoparticles at the interface, which results in a non-monotonous mechanical reinforcement.
Supervisor: Mostofi, Arash ; Sutton, Adrian Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral