Experimental and theoretical investigation of novel (semi-) conducting nanocomposites based on carbon nanotubes

Abstract

In this work the potential use of polydimethylsiloxane (PDMS) and polymethylphenylsiloxane (PMPS) in blends with polystyrene (PS) as a matrix for conductive carbon nanotube (NT) nanocomposites was studied. In accordance with the double percolation theory, it is expected that low amounts of NTs will be sufficient to achieve conductivity. For this purpose, nanocomposites of pure PDMS and PMPS as well as blends with PS were studied using modulated temperature differential scanning calorimetry (MTDSC), rheometry, conductivity measurements, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Additionally, semi-empirical AM1 calculations were used to theoretically investigate the interaction between different polymers and NT. A very good dispersion and debundling of NTs in both PDMS and PMPS is indicated by rheometry and conductivity measurements. Indicatie betere interactie met een van de twee? Spin coating in conjunction with AFM and MTDSC was used to determine the stability of both compatibilized and uncompatibilized blends of PDMS or PMPS with PS. In accordance with literature, the PS/PDMS system was found to be highly immiscible by both experimental techniques as theoretical calculations. While compatibilization with block copolymers increased the stability of PS/PDMS blends, thermally stable blends were not observed. On the other hand, PMPS was found to be partially miscible with PS by MTDSC measurements, while theoretically a favourable interaction was also calculated. Such blends were more stable and did not require compatibilization, prompting their use with NTs. Bulk samples of PS/PMPS with NTs were prepared by both solvent mixing and extrusion. AFM and SEM gave clear indications that NTs were found in the PMPS phases when dispersed in this component before extrusion with PS.

Date of Award	1 Jul 2009
Original language	English
Supervisor	Bruno Van Mele (Promotor), Paul Geerlings (Promotor), Gregory Van Lier (Co-promotor), Guy Van Assche (Jury) & Nicolaas-Alexander Gotzen (Advisor)