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Title: Wetting of pulsed plasma fluoropolymers
Author: Milnes-Smith, Eleanor
ISNI:       0000 0004 8507 2889
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2019
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The work presented in this thesis is an investigation of the surface properties of fluoropolymers synthesized via pulsed plasma polymerization. The focus is on perfluoroalkyl acrylate (PFAC-n, where n is the number of carbons in the perfluoroalkyl chain) polymers which are used in the manufacture of military protective clothing. The aim of the study is to understand how PFAC-n polymer surfaces interact with liquids, particularly chemical warfare agents (CWA's). The properties of some other fluoropolymers are also briefly investigated; the acrylate group in PFAC-6 is exchanged for an alkene (PFO) and a perfluoroalkyl (PFH) group. Additionally, a co-polymer of PFAC-6 and 2-hydroxyethyl methacrylate (HEMA) was synthesized which shows good potential for use in oil/water separation. The surfaces were characterized using 19F solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle goniometry. It is shown that plasma conditions resulted in degradation of PFO and PFH, whilst PFAC-n polymerizes with retention of functionality. PFAC-4 and -6 exist in the liquid state at room temperatures, whilst PFAC-8 and -10 are disordered polycrystalline solids. All show increased side-chain ordering at the surface compared to the bulk, with preferential segregation of CF3 at the surface. The two liquids have increased ordering compared to the solids at room temperature and are therefore lower in surface energy. The time- and temperature-dependence of contact angles of ethylene glycol (EG) and n-hexadecane (n-HD) is investigated, and these are shown to trigger surface reorganization of PFAC-n when the polymers are in the liquid state. The wetting behaviour of some CWA's and CWA simulants is also examined, and it was found that the CWA's display lower contact angles on PFAC-n than predicted by the wetting of conventional probe liquids, such as ethylene glycol and n-hexadecane, or by the wetting of CWA simulants.
Supervisor: Perkin, Susan Sponsor: Defence Science and Technology Laboratory
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physical Chemistry ; Surface Science ; Wetting ; Polymer Science ; Chemistry ; Materials Science