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B10.05 - Molecular Disorder in Prestrained Nanocomposites: Effects of Processing on Durability of Thermally-Active Ethylene-Vinyl Acetate | PyChol | Multiwall Carbon Nanotubes 
December 3, 2014   9:15am - 9:30am
  Synced Audio / Video / Slides

The discovery of carbon nanotubes (CNTs) has stirred a vast research interest in many academic disciplines, from materials to neuroscience, thanks to their extraordinary mechanical, electrical, thermal and optical properties. The ability to fine-tune these properties through functionalization and introduction into various host systems makes CNTs promising candidates as nanofillers in a myriad of foreseen applications. Additionally, certain ‘smart’ polymer-CNT nanocomposites have shown mechanically-active behaviour, responding mechanically when irradiated by external stimuli.

Near-edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is an invaluable technique to characterise such systems as it is able to probe the interactions at the filler-matrix interface with very high energy resolution, and can identify conformational behaviour. It also allows for in-situ analysis of smart materials. We had examined variations in NEXAFS spectra of thermo-active Ethylene-Vynil Acetate (EVA) |CNT composites, and offered an actuation model based on ‘kinking’ and twisting CNTs upon excitation. The model confirms the importance of filler alignment, induced here by straining, for coherent actuation response, where dispersant PyChol molecules latched to CNTs by π-π interactions. 1

We have found however, that molecular durability of EVA|CNT is a strong function of processing.2 Indeed, we now report on the effects of π-π aging due to sonication and straining during processing. We report significant spectral variations on in-situ temperature-resolved NEXAFS analysis of aged composites. Supported by AFM phase topography, interactions between filler and dispersant are observed to be compromised, interrupting communication between filler and polymeric host by way of PyChol segregation. By analysing the evolution of conformational relations in fresh and 1 year-aged composites, a quantitative account has been provided, where sonication and straining promote unlatching of 20% and 76% of PyChol molecules; effectively frustrating actuation.


1 A.D. Winter; E. Larios, F.M. Alamgir; C. Jaye; D. Fischer, M. Omastová; E.M. Campo, Thermo-Mechanical Actuation of EVA-CNT Composites by in-Situ near Edge X-Ray Absorption Fine Structure. The Journal of Physical Chemistry C, 2014, 118 (7), pp 3733-3741
2 A. D. Winter, C. Jaye, D. Fischer, M. Omastov' a, and E. M. Campo, Prestrain relaxation in non-covalently modified ethylene-vinyl acetate | PyChol | multiwall carbon nanotube nanocomposites, Applied Physics Letters Materials 2, 000000(2014)

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