Dissipative Particle Dynamics Simulation of Ionic Liquid-Based Microemulsion: Quantitative Properties and Emulsification Mechanism

Effect of sequence distribution of block copolymers on the interfacial properties of ternary mixtures: a dissipative particle dynamics simulation

In this paper, the dissipative particle dynamics (DPD) simulations method is used to study the effect of sequence distribution of block copolymers on the interfacial properties between immiscible homopolymers. Five block copolymers with the same composition but different sequence lengths are utilized for simulation. The sequence distribution is varied from the alternating copolymer to the symmetric diblock copolymer. Our simulations show that the efficiency of the block copolymer in reducing the interfacial tension is highly dependent on both the degree of penetration of the copolymer chain into the homopolymer phase and the number of copolymers at the interface per area. The linear block copolymers AB with the sequence length of τ = 8 could both sufficiently extend into the homopolymer phases and exhibit a larger number of copolymers at the interface per area. Thereby the copolymer with the sequence length τ = 8 is more effective in reducing the interfacial tension compared to that of diblock copolymers and the alternating copolymers at the same concentration. This work offers useful tips for copolymer compatibilizer selection at the immiscible homopolymer mixture interfaces.

DPD Study on the Interfacial Properties of PEO/PEO-PPO-PEO/PPO Ternary Blends: Effects of Pluronic Structure and Concentration

Using the method of dissipative particle dynamics (DPD) simulations, we investigated the interfacial properties of PEO/PEO-PPO-PEO/PPO ternary blends composed of the Pluronics L64(EO₁₃PO₃₀EO₁₃), F68(EO₇₆PO₂₉EO₇₆), F88(EO₁₀₄PO₃₉EO₁₀₄), or F127(EO₁₀₆PO₇₀EO₁₀₆) triblock copolymers. Our simulations show that: (i) The interfacial tensions (γ) of the ternary blends obey the relationship γF68 < γL64 < γF88 < γF127, which indicates that triblock copolymer F68 is most effective in reducing the interfacial tension, compared to L64, F88, and F127; (ii) For the blends of PEO/L64/PPO and the F64 copolymer concentration ranging from c_cp = 0.2 to 0.4, the interface exhibits a saturation state, which results in the aggregation and micelle formation of F64 copolymers added to the blends, and a lowered efficiency of the L64 copolymers as a compatibilizer, thus, the interfacial tension decreases slightly; (iii) For the blends of PEO/F68/PPO, elevating the Pluronic copolymer concentration can promote Pluronic copolymer enrichment at the interfaces without forming the micelles, which reduces the interfacial tension significantly. The interfacial properties of the blends contained the PEO-PPO-PEO triblock copolymer compatibilizers are, thus, controlled by the triblock copolymer structure and the concentration. This work provides important insights into the use of the PEO-PPO-PEO triblock copolymer as compatibilizers in the PEO and PPO homopolymer blend systems.

Effects of Repulsion Parameter and Chain Length of Homopolymers on Interfacial Properties of An/Ax/2BxAx/2/Bm Blends: A DPD Simulation Study

We explored the effects of the repulsion parameter (aAB) and chain length (N_HA or N_HB) of homopolymers on the interfacial properties of A_n/A_x/2B_xA_x/2/B_m ternary polymeric blends using dissipative particle dynamics (DPD) simulations. Our simulations show that: (i) The ternary blends exhibit the significant segregation at the repulsion parameter (aAB = 40). (ii) Both the interfacial tension and the density of triblock copolymer at the center of the interface increase to a plateau with increasing the homopolymer chain length, which indicates that the triblock copolymers with shorter chain length exhibit better performance as the compatibilizers for stabilizing the blends. (iii) For the case of N_HA = 4 (chain length of homopolymers A_n) and N_HB (chain length of homopolymers B_m) ranging from 16 to 64, the blends exhibit larger interfacial widths with a weakened correlation between bead A_n and B_m of homopolymers, which indicates that the triblock copolymer compatibilizers (A_x/2B_xA_x/2) show better performance in reducing the interfacial tension. The effectiveness of triblock copolymer compatibilizers is, thus, controlled by the regulation of repulsion parameters and the homopolymer chain length. This work raises important considerations concerning the use of the triblock copolymer as compatibilizers in the immiscible homopolymer blend systems.

Dissipative Particle Dynamics Study on Interfacial Properties of Symmetric Ternary Polymeric Blends

We investigated the interfacial properties of symmetric ternary A_n/A_mB_m/B_n and A_n/A_m/2B_mA_m/2/B_n polymeric blends by means of dissipative particle dynamics (DPD) simulations. We systematically analyzed the effects of composition, chain length, and concentration of the copolymers on the interfacial tensions, interfacial widths, and the structures of each polymer component in the blends. Our simulations show that: (i) the efficiency of the copolymers in reducing the interfacial tension is highly dependent on their compositions. The triblock copolymers are more effective in reducing the interfacial tension compared to that of the diblock copolymers at the same chain length and concentration; (ii) the interfacial tension of the blends increases with increases in the triblock copolymer chain length, which indicates that the triblock copolymers with a shorter chain length exhibit a better performance as the compatibilizers compared to that of their counterparts with longer chain lengths; and (iii) elevating the triblock copolymer concentration can promote copolymer enrichment at the center of the interface, which enlarges the width of the phase interfaces and reduces the interfacial tension. These findings illustrate the correlations between the efficiency of copolymer compatibilizers and their detailed molecular parameters.