Encapsulating carbon nanotubes in aqueous ds-DNA anisotropic phases: shear orientation and rheological properties

Carbon nanotubes reinforce polymer composites providing nanotube-based nanohybrids with potentially outstanding properties. The dispersion quality, however, influences the performances of the resulting materials. Therefore, new preparation procedures and efficient dispersion strategies are needed. A new method encapsulating single-walled carbon nanotubes in a nematic phase of double stranded DNA-water-NaCl is reported here. The procedure relies on osmotic compression and on its role in compacting DNA-nanotube composites. An anionic polymer (sodium dextransulfate) was added to the above dispersions and segregative phase separation was induced. DNA-nanotube composites were concentrated and phase-separated from the coexisting polymer solution. In this way, high concentrations of carbon nanotubes can be incorporated in the DNA-rich phase, inducing a transition from liquid- to solid-like behavior. The resulting nematic fluids are homogeneous and orient when shear stresses are applied. The kinetics of re-alignment was determined by rheological and spectroscopic methods. The effect of the nanotubes on the resulting behavior was accounted for. A slowing down of DNA motion observed in such composite matrices suggests interactions with nanotubes.