**3. MD simulations of ethanol-hexane (1:1) mixed solution and disordered MBBA molecular system**

MD simulations of a mixed solution of hexane and ethanol were performed under conditions with and without an oscillating external electric field using Gromacs-2018.7 [45], with the CHARMM36 force field [46]. The CHARMM36 parameter of the MBBA molecule was generated by CHARMM General Force Field (CGenFF) software [47]. Two different systems were applied. The first system consists of 4500 hexane and 4500 ethanol molecules randomly inserted in a cubic box with an edge size of 11.4 nm. The second system includes 904 arbitrarily oriented MBBA molecules in a cubic box with an edge size of 7.5 nm. Periodic boundary conditions were used in all directions, and an oscillating electric field was applied along the x-axis for both systems. An applied electric field with an intensity of 0.5 V/nm and a frequency of 2.45 GHz that served as the microwave heating process [48] was implemented in the simulations. The systems were minimized using steepest descent minimization to reduce steric clashes and were then equilibrated under a constant number of atoms, volume, and temperature (NVT), and under a constant number of atoms, pressure, and temperature (NPT) for each 100-ps MD run. A simulation of the mixture of ethanol and hexane was conducted without the applied electric field for 50 ns. The last snapshot of the simulation was applied as an initial configuration of eight simulations for 5 ns each at different temperatures of 303, 313, 323, and 333 K in the presence and absence of the electric field. In the case of the MBBA system, the initial simulation was performed for 10 ns. The temperature of 293 K (<liquid crystalline to isotropic phase transition temperature (Tc)) and 315 K (>Tc) were then considered with and without the external electric field. The temperature was controlled by a velocity-rescale thermostat [49], and a Parrinello-Rahman barostat provided 1 atm pressure during the simulations [50]. The particle mesh Ewald method [51, 52] and a cutoff of 14 Å were applied for the long-range electrostatic and short-range nonbonded interactions, respectively. The LINCS algorithm was used to constrain all bonds to equilibrium lengths [53]. The time steps of the simulations were 1 and 2 fs for the hexane-ethanol and MBBA systems, respectively. The data were saved at 1 ps intervals. Gromacs tools were used for data analysis; Grace [54] and VMD [55] software were applied for the plots and the structural representations, respectively.

**173**

**Figure 2.** *<sup>1</sup>*

*H chemical shift changes from 1*

*permission from [34]. Copyright (2020) American Chemical Society.*

*Microwave Heating of Liquid Crystals and Ethanol-Hexane Mixed Solution and Its Features…*

The *in situ* temperatures of the ethanol-hexane mixed solution and MBBA in the isotropic state under microwave irradiation were assessed with respect to the

of OH, CH2, and CH3 protons in ethanol (**Figure 2a**) and the CH2 and CH3 protons in hexane (**Figure 2b**) that were observed under temperature control with the NMR

Δδ plotted as a function of temperature was approximately linear within

spectra of individual protons were measured in the same sample at the same position in the probe and the temperature variation was measured under microwave irradiation. The *in situ* temperatures (CSC-temperature) of the individual protons in the sample solution under microwave irradiation were thus evaluated

*in situ* temperature of the bulk solution was accurately determined with the CSC*-*temperature for individual non-polar proton groups under microwave

H chemical shifts with temperature for the sample solution located in

H chemical shift changes from that at 0°C (Δδ) were plotted as a

*H chemical shift at 0°C (*Δδ*) for (a) ethanol OH, CH2, and CH3 protons* 

*and (b) hexane CH2 and CH3 protons as a function of temperature in the range from 0-60°C. Adapted with* 

H chemical shifts. It is stressed that the

H NMR signals

H NMR

**4.** *In situ* **temperature measurements under microwave irradiation**

the NMR probe. **Figure 2** shows the temperature dependence of the 1

a small temperature range, as observed in methanol and glycol [40]. <sup>1</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.97356*

variation in 1

irradiation.

spectrometer. The 1

function of the temperature.

using the temperature variation of the <sup>1</sup>

*Microwave Heating of Liquid Crystals and Ethanol-Hexane Mixed Solution and Its Features… DOI: http://dx.doi.org/10.5772/intechopen.97356*
