Self-assembly behavior of ABA coil-rod-coil triblock copolymers: A Brownian dynamics simulation approach

Abstract

The self-assembly behavior of ABA coil-rod-coil triblock copolymers in a selective solvent was studied by a Brownian molecular dynamics simulation method. It was found that the rod midblock plays an important role in the self-assembly of the copolymers. With a decrease in the segregation strength, ɛ(RR), of rod pairs, the aggregate structure first varies from a smecticlike disk shape to a long twisted string micelle and then to small aggregates. The influence of the block length and the asymmetry of the triblock copolymer on the phase behavior were studied and the corresponding phase diagrams were mapped. It was revealed that the variation of these parameters has a profound effect on microstructure. The simulation results are consistent with experimental results. Compared to rod-coil diblock copolymers, the coil-rod-coil triblock copolymers has a larger entropy penalty associated with the interfacial grafting density of the aggregate, leading to a higher ɛ(RR) value for structural transitions.

Aggregation Behavior of Rod–Coil–Rod Triblock Copolymers in a Coil-Selective Solvent

“…In comparing our results to those reported in simulations for coil−rod−coil BCPs, 19 we observe that rod−coil−rod exhibits similar structures (we note that Li et al did not report cluster characteristics) at segregation strengths that are comparatively lower. However, in contrast to the situation for coil−rod−coil BCPs, we did not see structures possessing long-range order (such as the disk morphologies reported by Li et al) despite increasing the segregation strength to several k B T. We reason that this is due to the increased entropic penalty associated with a middle coil block versus the end coil blocks in forming these types of structures.…”

“…The ratio of the distance between peaks is seen to be consistent with hexagonal packing of the rods, a result that was also observed in simulations of coil− rod−coil chains. 19 Interestingly, the rod constituents of the string-like aggregates are stacked perpendicularly to the long axis of the aggregate (see Figure 1b), and resemble amyloid fibrils seen in β-sheet stacked proteins. 26 Indeed, it has been shown through experiments and atomistic MD simulations that fibrils resembling those formed by natural proteins can be made through the aggregation of short aliphatic peptide sequences.…”

“…These parameters are similar to those employed by Li et al in their modeling of coil−rod−coil polymers in solution. 19 The intermolecular potential between beads was chosen to be a standard shifted and truncated Lennard-Jones (LJ) 6-12 potential of the form: For simplicity, σ ij is assumed to be the same (and denoted as σ in this Article) for all pairwise interactions. To mimic the fact that the rod monomers are in a poor solvent, the LJ cutoff distance for rod monomers, r AA c , is set to 2.5σ, ensuring attractive interactions between rod monomers.…”

Self-assembly of rod-coil-rod triblock copolymers: A route toward hierarchical liquid crystalline structures

“…The BD simulations can be used to investigate the self-assembly of the M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 rod-coil-rod copolymers due to their success in studying the phase behavior of the copolymers with rod blocks. [29][30][31][46][47][48] For example, Glotzer et al performed BD simulations on rod-coil diblock copolymers, and obtained various LC phases, including cubic phase, smectic C phase, tetragonally perforated lamellar phase, and honeycomb phase. 31 The morphologies of LC structures were found to be dependent of rod aspect ratio, coil length, and temperature.…”

Dissipative Particle Dynamics Simulation on Self‐Assembly Behavior of Rod–Coil–Rod Triblock Copolymer in Solutions

“…The rod–coil block copolymers include various chain architectures. Among them, the common linear diblock rod–coil copolymer has been given more attention . In melts, various morphologies (including smectic, columnar, perforated lamellar, bicontinuous, arrowhead, and wavy lamellar or zigzag phases) have been observed by experiments .…”