DFT Studies of Selected Epoxies with Mesogenic Units–Impact of Molecular Structure on Electro-Optical Response

Abstract

Theoretical studies of molecular structure and electric charge distribution were carried out for three epoxy compounds with different mesogenic cores. The compounds exhibit a nematic phase and form polymer networks that are potential bases for various composites. Results were compared to analogous materials with non-polar chains. A customized process involving geometry optimization of a series of conformations was employed to greatly increase likelihood of reaching global energy minimum for each molecule. All computations used Density Functional Theory (DFT) electron correlation model with the B3LYP hybrid functional. Molecular structure calculations yielded several parameters, including the magnitude and direction of the dipole moment, polarizability (α), first hyperpolarizability (β), and highest-occupied/lowest-unoccupied molecular orbital (HOMO-LUMO) energies. These parameters can help predict electronic properties of the nematic phase and the polymer network and assess their predisposition for application in electrooptical devices. In particular, the magnitude and direction of the dipole moment determine molecular alignment of liquid crystal phases in electric field, which enables controlling molecular order also in cured networks. Theoretical results were supplemented with observations of the nematics and their behavior in electric field. It was demonstrated for the studied compounds that a change in aliphatic chain polarity helps preserve and reinforce perpendicular alignment of molecules induced by electric field.

UV light sensing and switching applications of dimeric smectic liquid crystals: comparative calculations

“…The hybrid functional execution suggests the consistent excitation of vertical energies together with analysis of charge transfer. Therefore, the structure-based aspects have been analysed via the ‘hybrid’ density B3LYP functionals [ 31 – 33 ] and ‘precise exchange’ in coupling with the gradient-suitable density functionals. Further, the structural optimization process has been performed via the DFT-B3LYP approach [ 34 , 35 ], along with 6-31G+(d) basis set.…”

“…This procedure has been widely accepted and sufficient to guesstimate the absorption spectra in UV-visible region. The SORCI (spectroscopy-oriented configuration interaction) method [ 31 , 36 ] has been used for the DFT calculations. The DFT data has been matched up with the CNDO/S + CI and INDO/S + CI approaches.…”

Impact of Mendong fiber–epoxy composite interface properties on electric field frequency exposure

“…52 Electric field-induced dipole results in the movement of the polar group following the external electric field direction, 53 and the nematic phase of epoxy is molecularly aligned during the curing process. 54 During the polymerization process, the viscosity of the matrix generated an electrodynamics flow due to the influence of electric field application allowing the particle orientation and the chain-like structure formation. 55 The orientation of the structure produced an anisotropic polymer having different mechanical and physical properties.…”

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

“…This direction is represented by 39 articles [ 28 , 35 , 129 , 134 , 136 , 190 , 191 , 192 , 193 , 194 , 195 , 196 , 197 , 198 , 199 , 200 , 201 , 202 , 203 , 204 , 205 , 206 , 207 , 208 , 209 , 210 , 211 , 212 , 213 , 214 , 215 , 216 , 217 , 218 , 219 , 220 , 221 , 222 , 223 ]. Their distribution, according to the above types, is presented in Table 7 .…”

“…This expectation is fully consistent with reality, since most of the articles in this direction (31 of 39) are precisely the articles in groups ( b ) and ( c ). Moreover, the articles in group ( b ) constitute the largest part of all the articles related to Thematic Area 6; these include [ 35 , 134 , 190 , 191 , 196 , 197 , 198 , 201 , 203 , 205 , 206 , 207 , 211 , 216 , 217 , 218 , 219 ]. For formal reasons, the list of just cited references can also include the original article [ 208 ] and the review [ 220 ] devoted to graphene and fullerenes, since they all contain carbon–carbon bonds, and, according to the IUPAC standards, they should be classified as organic compounds (although, in general, this means that all chemical compounds consisting of atoms of only one chemical element are traditionally considered objects of inorganic chemistry).…”