Dissipative Particle Dynamics Simulation of the Phase Behavior of T-shaped Ternary Amphiphiles Possessing Long Rod-like Mesogens†

doi:10.7503/cjcu20130583

Abstract

Abstract:

Using dissipative particle dynamics simulations, a phase diagram in terms of temperature and lateral chain length was established, related structural parameters and the effective volume fraction of lateral chains f_L related to each mesophase were calculated.The experimentally observed pentagonal, hexagonal columnar phase and the lamellar phase where rods are stacked with in-plane order are firstly reproduced. The results show that the phase sequence and structures in the diagram of T-shaped ternary amphiphilies with long rod-like mesogens agree well with previous reports, the effective volume fraction of lateral chains f_L related to each mesophase is also quantitatively consistent with the experimental value. These combined results demonstrate that the coarse graining model in our simulation reflects essential structural features of T-shaped real mo-lecules like molecular topology, excluded volume effects, tendency to phase separation, the length-to-width ratio of rod liquid crystal unit and the spatial effects of lateral chains, and they also confirm the fact that the size of lateral chains plays an important role in affecting the self-assembled structures of nonlinear systems and the distribution of each constituent.

Key words: T-shaped ternary amphiphilie, Phase behavior, Dissipative particle dynamics simulation

CLC Number:

O631

TrendMD:

LIU Xiaohan, GUO Hongxia. Dissipative Particle Dynamics Simulation of the Phase Behavior of T-shaped Ternary Amphiphiles Possessing Long Rod-like Mesogens^†[J]. Chem. J. Chinese Universities, 2014, 35(2): 440.

Figures/Tables 9

Fig.1 T-shaped coarse-graining model used in our simulation

Table 1 Repulsion parameters(aij) for the coarse-graining model

j	i=Rod	i=End	i=Lateral
Rod	15	40	40
End	40	20	40
Lateral	40	40	20

Table 2 Parameters for the harmonic bending potential for the coarse-graining model*

System	k_θ	θ₀/(°)	System	k_θ	θ₀/(°)
E1R2R3	4.0	180	R2R3L7	4.0	90
R2R3R4	4.0	180	R4R3L7	4.0	90
R3R4R5	4.0	180	R3L7L8	2.0	180
R4R5E6	4.0	180	L7L8L9	2.0	180

Fig.2 Graphical representation of the mesophases obtained upon varying the reduced temperature for the different molecular conformations studied(varying the number of grafted side beads)

Fig.3 Quantitative characterization of SmA phase for E1R4L1 at T=0.8(A) Snapshot of the equilibrium configuration, viewed perpendicular to the direction of the plane normal, blue spheres represent the terminal chains, cyan spheres represent the rigid rodlike core, red spheres represent the side grafted chains; (B) structure factor of the graft position of side chains.

Fig.4 Quantitative characterization of Colsqu/P4mm phase for E1R4L2 at T=0.8(A, B) and Colhex/P6mm phase for E1R4L5 at T=1.4(C, D)(A) and (C) Snapshot of the equilibrium configuration, viewed along the cylindrical axis; (B) and (D) structure factor of the last bead of side chains. The solid lines in(A) and (C) are depicted to highlight unit cells with polygonal shapes.

Fig.5 Angle distribution function f(θ) of Colsqu/P4mm phase for E1R4L2 at T=0.8(A) and Colhex/p6mm phase for E1R4L5 at T=1.4(B)

Fig.6 Quantitative characterization of Colsqu1/P4gm phase for E1R4L4 at T = 1.0(A, B) and Colhex/C2mm phase for E1R4L8 at T=0.8(C, D)(A) and (C) Snapshot of the equilibrium configuration, viewed along the cylindrical axis; (B) and (D) angle distribution function f(θ). The solid lines in(A) and (C) are depicted to highlight unit cells with polygonal shapes.

Fig.7 Quantitative characterization of Lamiso phase for E1R4L8 at T = 2.4(A, B) and Lamsm phase for E1R4L10 at T=0.7(C, D)(A) and (C) Snapshot of the equilibrium configuration of respective Lamiso and Lamsm phase, viewed perpendicular to the plane normal; (B) structure factor of the graft position of side chains; (D) snapshot of Lamsm phase in equilibrium without lateral beads, viewed along the plane normal.

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