  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 concentration 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.
