Dispersion of carbon-based materials (CNTs, Graphene) in polymer matrices

Polymer composites containing carbon-based fillers have recently received consi-derable attention due to their remarkable properties (i.e. mechanical, electrical, thermal and optical) together with low weight, easy processing. Among the main carbon-based fillers, carbon nanotubes (CNTs), expanded gra-phite (EG), graphite nanoplateles (GNPs), graphene oxide (GO) and graphene (GR) attracted considerable attention in a great variety of applications such as chemical and biosensors, energy storage materials, field effect transistors, polymer composites, etc. In particular, CNTs and GRs are considered ideal materials for preparing “metal-free” conductive polymer composites [1-7] or for reinforcing materials with potential applications in aerospace and automotive sectors, where lightweight and robust materials are needed [8]. Basically, the excellent properties of CNTs (SWCNTs, MWCNTs) and of GRs-based systems alone, as reported in Table 1, are related to individual or quasi-isolated species. It is well documented that such properties are strongly affected by type, structure and cristallinity of the nanotubes as well as by the exfoliation degree of the layered species (i.e. graphene like systems) (Table 1). In more de-tails, the higher is the quality of materials (i.e. CNTs produced by arc-discharge methods) the more advanced are the properties [9]. On the other hand, the peculiar crystalline structure of graphite, having delocalized electrons, which are free to move throughout the basal planes, originate the well known electrical and thermal conductivities (see Table 1). Anymore the presence of in the plane C-C bonds causes the graphite to have an in-plane modulus of 130GPa [9]. However, these properties are hard to be find in composites, as the pristine CNTs and GRs, usually organized in bundles or in stacked species, needs further treat-ments (e.g. purification, separation, functionalization, debundling/exfoliation and/or GO reduction, etc.) before to be used, which partially modifies their struc-ture and then their peculiar properties. Nevertheless, especially noteworthy are the synergistic effects between CNTs and graphene nanostructures inside the composite materials. Refs: [1] Kordas K, Mustonen T, Toth G, Jantunen H, Lajunen M, Soldano C, et al. Inkjet Printing of Electrically Conductive Patterns of Carbon Nanotubes. Small. 2006;2(8-9):1021-5. [2] Kim S-m, Kim J, Lim J, Choi M, Kang S, Lee S, et al. Nanoimprinting of conductive tracks using metal nanopowders Applied Physics Letters. 2007;91(14):143117-20. [3] Cho J, Shin K-H, Jang J. Micropatterning of conducting polymer tracks on plasma treated flexible substrate using vapor phase polymerization-mediated inkjet printing. Synth Met. 2010;160(9-10):1119-25. [4] Gao W, Singh N, Song L, Liu Z, Reddy ALM, Ci L, et al. Direct laser writing of micro-supercapacitors on hydrated graphite oxide films Nat Nanotechnol. 2011;6(8):496-500. [5] Cesano F, Rattalino I, Bardelli F, Sanginario A, Gianturco A, Veca A, et al. Structure and properties of metal-free conductive tracks on polyethylene/multiwalled carbon nanotube composites as obtained by laser stimulated percolation. Carbon. 2013;61(September 2013):63-71. [6] Cravanzola S, Haznedar G, Scarano D, Zecchina A, Cesano F. Carbon-based piezoresistive polymer composites: structure and electrical properties. Carbon. 2013;62(October 2013):270–7. [7] Haznedar G, Cravanzola S, Zanetti M, Scarano D, Zecchina A, Cesano F. Graphite nanop-latelets and carbon nanotubes based polyethylene nanocomposites: electrical conductivity and morphology. Materials Chemistry and Physics. 2013;143(1):47–52. [8] Veedu VP, Cao A, Li X, Ma K, Soldano C, Kar S, et al. Multifunctional composites using reinforced laminae with carbon-nanotube forests. Nature Mater. 2006;5:457-62 [9] Coleman JN, Khan U, Blau WJ, Gun'ko YK. Small but strong: A review of the mechanical properties of carbon nanotube-polymer composites. Carbon. 2006 Aug;44(9):1624-52.