Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491172
Title: Interfacial interactions in polymer layered silicate nanocomposites
Author: Kato, Ryo
Awarding Body: Manchester Metropolitan University
Current Institution: Manchester Metropolitan University
Date of Award: 2008
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Abstract:
Polymer layered silicate nanocomposites (PLSN) have attracted great interest because they exhibit remarkable improvements in materials properties relative to pristine polymers. Successful formation of a PLSN is critically dependent on generation of very high interfacial area in the composite. This is accomplished when the stacks of silicate platelets (tactoids) split into discrete platelets. The latter phenomenon is known as exfoliation and is strongly influenced by interfacial chemistry (i.e. structure and properties of the interface or interphase) associated with the edge and basal surfaces of the silicate platelets, chemical modification (usually with quaternary alkyl ammonium halides) of the latter and the resulting effect on interactions between the platelets themselves and polymer chains. Interactions between sodium montmorillonite (Na-MMT)/organically modified montmorillonite (o-MMT) and a variety of probes, some of which are intended to model the structures present in the components of a polyurethane (PU), epoxy resin and polystyrene system (PS), have been studied. The adsorption process was characterised using flow microcalorimetry (FMC) in conjuncqon with diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and wide angle x-ray scattering (\VAXS). Adsorption of hydrogen bondable groups, such as alcohol, ether, amine probes, onto Na-MMT was dominated by the hydrogen bonding interactions with hydrated Na+ ions and with the hydroxyl groups present at the platelet edges. Moreover, stronger interactions with hydrated Na+ ions led to greater retention of the probes after the desorption process. When the Na-MMT was moisturized at ambient atmosphere, hydrogen bondable probes showed a reversible adsorption. In contrast, chemical adsorption (reaction) dominated the adsorption of the isocyanate probe onto Na-MMT; the latter reacted either with the platelet edge hydroxyl groups forming a urethane linkage or with pre-adsorbed ambient water molecules adsorbed onto Na-MMT ultimately forming a physically adsorbed urea. In the case of o-MMTs, when only the platelet edge hydroxyl groups were available, hydrogen bondable probes showed a reversible adsorption. Reactions between reactive probes, including isocyanate and epoxide probes, and surfactant functional groups (OH and COOH groups) are affected by the gallery structures, such as the arrangement of surfactant within the galleries and level of surfactant intercalated. Adsorption of aromatic probes, including styrene, ethylbenzene and polystyrene, was dominated by the relatively weak dispersive interactions with the basal surfaces of o-MMT, and was significantly affected by the gallery structures ofo-MMT (surfactant level and surfactant structure). This study has provided valuable new insight into interactions in nanocomposite materials.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.491172  DOI: Not available
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