The microstructure and electrical conductivity of suspensions of multi-walled carbon nanotubes (MWCNTs) in binary liquid mixtures water-1-Cyclohexyl-2-pyrrolidone (CHP) were studied in the heating and cooling cycles. The concentration of MWCNTs was v
aried in the interval between 0-1 wt.% and the content of water in a binary mixture X = [water]/([CHP]+[water]) was varied within 0-1.0. The experimental data have shown that dispersing quality of MWCNTs in a mixture of good (CHP) and bad (water) solvents may be finely regulated by adjustment of composition of the CHP+ water mixtures. The aggregation ability of MWCNTs in dependence on X was discussed. The surface of MWCNT clusters was highly tortuous, its fractal dimension df increased with increase of X, approaching -> 1.9 at X->1. It was concluded that the surface tension is not suitable characteristic for prediction of dispersion ability in the mixture of good and bad solvents. The electrical conductivity data evidenced the presence of a fuzzy-type percolation with multiple thresholds in the systems under investigation. This behavior was explained by formation of different percolation networks in dependence of MWCNT concentration.
The effects of multiwalled carbon nanotubes (NTs) on low-temperature phase transformations in 5CB were studied by means of differential scanning calorimetry (DSC), low-temperature photoluminescence and measurements of electrical conductivity. The con
centration of NTs was varied within 0-1% wt. The experimental data, obtained for pure 5CB by DSC and measurements of photoluminescence in the heating mode, evidenced the presence of two crystallization processes at T->229 K and T->262 K, which correspond to C1a->C1b, and C1b->C2 phase transformations. Increase of temperature T from 10 K to 229 K provoked the red shift of photoluminescence spectral band that was explained by flattening of 5CB molecule conformation. Moreover, the photoluminescence data allow to conclude that crystallisation at T=229 K results in conformation transition to non-planar 5CB structure characteristic to ideal crystal. The non-planar conformations were dominating in nematic phase, i.e., at T>297 K. Electrical conductivity data for NTs-5CB composites revealed supplementary anomaly inside the stable crystalline phase C2, identified earlier in the temperature range 229 K-296.8 K. It can reflect the influence of phase transformation of 5CB in interfacial layers on the transport of charge carriers between NTs.
