Polymer SWNT nanocomposites

A recently reported method for producing novel SWNT-polymer nanocomposites involved the use of self-assembled SWNT nanopaper films produced by vacuum filtration of SWNTs dispersed with surfactants in aqueous solution. The freestanding nanopaper films were soaked in a polymer resin followed by drying and hot pressing to form a composite in which the polymer is intercalated into the free volume between the SWNT bundles [64]. 

Ramanathan, T. Liu, H. Brinson, L.C. Functionalized SWNT/polymer nanocomposites for dramatic property enhancement J Polym. Sci. B Polym. Phys. 2005, 43 ... 

CNTs can enhance the thermal properties of CNT-polymer nanocomposites. The reinforcing function is closely associated with the amount and alignment of CNTs in the composites. Well-dispersed and long-term stable carbon nanotubes/ polymer composites own higher modulus and better thermal property as well as better electronic conductivity (Valter et al., 2002 Biercuk et al., 2002). Both SWNT and MWNT can improve the thermal stability and thermal conductivity of polymer, the polymer-CNT composites can be used for fabricating resistant-heat materials. 

Polymer nanocomposites with medium density polyethylene were reported with a variety of fluorinated and un-fluorinated nanotubes (37). The nanocomposites consisting of 1 wt% F-SWNT-C H (fluorinated and surface treated nanotubes) nanotubes showed an increase in tensile strength by 52.4%, modulus by 15.9% and elongation by 18.9% as compared to the pure polymer. The composites with 1 wt% F-SWNT-CnH23 (fluorinated and surface treated nanotubes) had an increase of 28.3% in modulus as compared to the pure polymer. The tensile strength also increased from 4.33 MPa for the pure polymer to 5.01 Mpa for the nanocomposite, the elongation at... 

Figure 2.17 CNT-polymer composite IR sensors. UV-Vis-near-IR spectra of (a) 5 wt% SWNTHiPco-PC and (b) 5 wt% SWNTcoMocat-PC composite thin films. Mil, Sii, and S22 represent optical transitions in metallic and semiconducting SWNTs, respectively.(c) Schematic experimental setup. Near-IR light covers all of the sample area, (d) Relative conductivity a (Jdark) responses of SWNT-PC nanocomposites to the on/off IR illumination (power intensity 7 mW mm ).

Transparent SWNT/insulating polymer nanocomposites have not been made with high conductivity values, mainly because of the intrinsic charge localization arising from insulating polymer dispersant. In a direct comparison, SWNTs were stabilized with insulating surfactant (SDS) or conductive poly(3,4-ethylenedioxythiophene) (PEDOT) PSS. " Both SWNT dispersions were introduced into a polystyrene matrix via a latex-based route. Composites with PEDOT PSS-stabilized SWNTs showed a percolation threshold of 0.18 wt% and a conductivity value of 500 S m compared with 3.8 wt% and 20 S m for the SDS-based composites, respectively. The authors attributed the conductivity enhancement to conduction bridge formed by the conductive polymer between adjacent SWNTs. 

The effect of S WNT addition to PANi fibers on conductivity was also investigated (Figure 8). A percolation threshold of 0.35% (w/w) SWNTs was determined using the basic percolation power law [32]. The value for conductivity percolation threshold obtained here is in good agreement with another polymer-nanocomposite system that showed a 0.5 w/w % percolation level [33]. In addition, a significant increase in electrical conductivity was observed even at low SWNTs loadings, while the neat PANi-AMPSA fibers prepared here had similar conductivities ( 500 Scm ) compared to those obtained in a previous study (600 Scm ) [11]. 

G.G. Silva, H.D.R. Calado, A.W. Musumeci, W. Martens, R.L. Frost, G.A. George, Polymer nanocomposites based on P30T, TPU and SWNT preparation and characterization, in Proceedings of the 2006 International Conference on Nanoscience and Nanotechnology, ICONN, 4143361, 2006, pp. 182-185. 

Another parameter influencing the mechanical properties of nanotube composites is the CNT alignment. The effects of CNT alignment on electrical conductivity and mechanical properties of CNT-polymer nanocomposites have been discussed in a number of researches [118-120]. For example, it has been reported that with increasing CNT alignment, the electrical and mechanical properties of the SWNT-epoxy composites increased due to an increased interface bonding of CNTs in the polymer matrix [119],... 

Foam-like MWNT/polymer nanocomposite has also been prepared by a method already described for silica foams (Cam et al., 2004). First, SWNTs were dispersed in water using carboxymethyl cellulose sodium salt and then a liquid foam was obtained via a bubbling process on a column (Leroy et al., 2007). This method allows control of the size and shape of cells by playing with the diameter of the porous filter and the liquid flux. Finally, the liquid foam was eooled down to -80°C and lyophilized. 

---