Columnar mesophases of hexabenzocoronene derivatives. I. Phase transitions

Abstract

Using atomistic molecular dynamic simulations we study the transitions between solid herringbone and liquid crystalline hexagonal mesophases of discotic liquid crystals formed by hexabenzocoronene derivatives. Combining a united atom representation for the side chains with the fully atomistic description of the core, we study the effect of side chain substitution on the transition temperatures as well as molecular ordering in the mesophases. Our study rationalizes the differences in charge carrier mobilities in the herringbone and hexagonal mesophases, which is predominantly due to the better rotational register of the neighboring molecules.

Molecular dynamics simulations of alkyl substituted nanographene crystals

“…Our MD simulations are able to predict the melting to the liquid-crystalline state, in agreement with similar computational work in the literature [19]. Unfortunately, the method fails to describe the reverse phenomenon of crystallisation below the transition temperature; the time scale of the atomistic MD simulation is apparently too short to sample the rare cooperative events whereby nucleation of the solid phase from the liquid crystal takes place.…”

“…A time step of 1 fs is used for all simulations and typical periodic boundary conditions are applied in every direction, simulating the systems in their bulk phase. As far as the force field is concerned, bonded interactions are modelled by a compilation of the generalised amber force field (GAFF) [28] and optimised potential for liquid simulations (OPLS) [29,30] force fields, together with a proper dihedral energy term proposed by Marcon et al [19] in order to account for the tendency of the side chains to arrange themselves in a perpendicular manner with respect to the polyaromatic cores. Atoms belonging to the polyaromatic cores are treated fully atomistically, while the atoms of the side chains are treated using a united atom representation, where the -CH 2 -and terminal -CH 3 groups are treated as superatoms, with the hydrogen atoms absorbed into the carbons.…”

“…The force field is generally described by Equation (1), where the primed dihedral angles refer to the term introduced by Marcon et al [19] with the parameterisation…”

Tilt orientationally disordered hexagonal columnar phase of phthalocyanine discotic liquid crystals

“…Thus, clarification of the discotic LC phase structure of these non-peripheral substituted Pcs is necessary. Molecular simulation is one possible tool to visualize the molecular-level LC phase structure [14,15] and to help understand its link to the carrier transport [16][17][18][19][20][21][22][23].…”

Multi-Scale Modeling of Bulk Heterojunctions for Organic Photovoltaic Applications

“…Time-resolved microwave conductivity (TRMC) measurements have shown that hole mobility in HBC is well above 0.1 cm 2 V −1 s −1 and depends on side chains (van de Craats et al, 1999). Atomistic simulations (Andrienko et al, 2006;Kirkpatrick et al, 2008;Marcon et al, 2008) performed on several HBC derivatives with different types of side chains (Figure 11) illustrate the dependence of morphology on semiconductor side chains. Alkyl side chains are generally added to polymers to improve Fig.…”