Synergistic effect of non-covalent interaction in colloidal nematic liquid crystal doped with magnetic functionalized single-walled carbon nanotubes

Abstract

Single-walled carbon nanotubes (SWCNTs), CNT@Fe3O4, and Fe3O4 nanocomposites were doped to eutectic uniaxial nematic liquid crystal (NLC's) (E5CN7) to improve physiochemical properties such as phase transition temperature, activation energy (Ea), dielectric anisotropy, and electro-optical properties. The thermal study of nematic phase shows a decrease in the nematic to isotropic phase transition temperature as CNT is doped. However, higher doping concentration of CNTs leads to the further increase in transition temperature. The anchoring effect or π-π interaction plays a key role in N-I phase transition. The functionalization of SWCNTs with Fe3O4 diminishes the CNT aggregation while the magnetic susceptibility is increased. The functionalized CNT doping to NLC's decrease significantly the phase transition temperature compared to doping of non-functionalized CNTs. Attractive interaction between guest and host molecules by magnetic and geometry effect increased the enthalpy and entropy of phase transition in the SWCNT@Fe3O4 sample compared to non-functionalized CNT doped system. Also, the Ea values are decreased as SWCNT@Fe3O4 is doped to pure E5CN7. The difference of N-I phase transition temperature was observed in Fe3O4 and CNT@Fe3O4 compared to SWCNT doped systems. Finally, dielectric anisotropy was increased in the doped system compared to pure NLC.

Electric‐Field‐Induced Alignment of Functionalized Carbon Nanotubes Inside Thermally Conductive Liquid Crystalline Polyimide Composite Films

“…The molar fraction of N atoms for LC‐CNT is 0.3 %, significantly lower than that of 7CB but slightly higher than that of CNT. This difference is attributed to the successful assembly of 5 wt % 7CB crystals on the surface of CNT in the LC‐CNT sample [32,33] . Figure 1d shows the thermogravimetric analysis (TGA) curves of 7CB, CNT and LC‐CNT.…”

“…This difference is attributed to the successful assembly of 5 wt % 7CB crystals on the surface of CNT in the LC-CNT sample. [32,33] Figure 1d shows the thermogravimetric analysis (TGA) curves of 7CB, CNT and LC-CNT. The thermal stability of 7CB is poor, and there is an obvious thermal weight loss step at 165 °C, and it is completely thermally decomposed at 300 °C.…”

Increased Nematic–Isotropic Transition Temperature on Doping a Liquid Crystal with Molecularly Rigid Carboxylic Acids

“…These molecular interactions can act as a support or scaffold for the LC molecules, consequently to induce greater orientational order in the nematic phases (Figure ). ,, Acids 5 and 6 cause the opposite effect due to their molecularly flexible aliphatic chains, which diminish the degree of order because of their molecular motion.…”

“…Despite the increased molecular order induced by the molecularly rigid acids, the enthalpies of the transitions (displayed in Table ) differed insignificantly at p = 0.03 (as determined with a Student’s t test), and the mean value was ⟨ ΔH ⟩ = 0.51 ± 0.01 kJ mol –1 . Nematic–isotropic transitions are considered to be weakly first-order; as the magnitudes of their enthalpies are related to the attractive interactions in the LC, the fact that these enthalpies do not alter on doping the LC with carboxylic acids indicates that interactions between 5CB molecules are not modified. Moreover, the interactions between the dopant and 5CB molecules are inferred to be similar to those established between 5CB molecules.…”

Recent progress and future perspectives on carbon-nanomaterial-dispersed liquid crystal composites

“…CNTs are dispersed in the nematic LCs via three methods: (a) CNTs are directly mixed with LCs, and subsequently, filtration of mixture to remove the unwanted graphite and amorphous carbon and sonication to obtain a homogeneous system; (b) CNTs are dispersed in an appropriate solvent before mixing with LC and the extra solvent is removed by evaporation; and (c) both surface encapsulation and covalent functionalization are used to functionalize CNTs before dispersing it in the LC. Dalir and Javadian [131] have studied the non-covalent interaction in colloidal nematic LC doped with magnetic functionalized single-walled carbon nanotubes. In this study, the authors have doped different amount of SWCNTs (0.25-1.0 wt%) and CNT@Fe 3 O 4 nanocomposite into a eutectic uniaxial nematic LC, namely E5CN7, and the physical properties along with the molecular orientation have been investigated.…”