Self-assembly of cyclic rod-coil diblock copolymers

Abstract

The phase behavior of cyclic rod-coil diblock copolymer melts is investigated by the dissipative particle dynamics simulation. In order to understand the effect of chain topological architecture better, we also study the linear rod-coil system. The comparison of the calculated phase diagrams between the two rod-coil copolymers reveals that the order-disorder transition point (χN)ODT for cyclic rod-coil diblock copolymers is always higher than that of equivalent linear rod-coil diblocks. In addition, the phase diagram for cyclic system is more "symmetrical," due to the topological constraint. Moreover, there are significant differences in the self-assembled overall morphologies and the local molecular arrangements. For example, frod = 0.5, both lamellar structures are formed while rod packing is different greatly in cyclic and linear cases. The lamellae with rods arranged coplanarly into bilayers occurs in cyclic rod-coil diblocks, while the lamellar structure with rods arranged end by end into interdigitated bilayers appears in linear counterpart. In both the lamellar phases, the domain size ratio of cyclic to linear diblocks is ranged from 0.63 to 0.70. This is attributed to that the cyclic architecture with the additional junction increases the contacts between incompatible blocks and prevents the coil chains from expanding as much as the linear cases. As frod = 0.7, the hexagonally packed cylinder is observed for cyclic rod-coil diblocks, while liquid-crystalline smectic A lamellar phase is formed in linear system. As a result, the cyclization of a linear rod-coil block copolymer can induce remarkable differences in the self-assembly behavior and also diversify its physical properties and applications greatly.

Coarse-Grained Modeling of Peptidic/PDMS Triblock Morphology

“…Considering a side view of a peptidic layer (Figure B), it is observed that the rigid polypeptide backbone aligns perpendicular to the lamellar plane, forming a smectic-like bilayer. This perpendicular organization is a common arrangement found within the rod-like segments of rod–coil and rod–coil–rod block copolymers due to the rods attempting to maximize rod–rod contact (enthalpy driven) while the coils expand to fill the free volume (entropy driven). − Furthermore, the bilayer formation, as opposed to interdigitation, is hypothesized to be triggered by the steric bulk of the benzyl-protected side chain and the relatively short polypeptide rod length. At the lamellar interface, the perpendicular peptidic rod packing causes a degree of coil elongation, decreasing the coil flexibility and inhibiting the space-filling ability within a small distance of the coil–rod interface.…”

Self-assembly and mesophase formation in a non-ionic chromonic liquid crystal system: insights from dissipative particle dynamics simulations

“…DPD has been successfully applied to simulate a number of soft matter systems: block co-polymers, [22][23][24] colloidal suspensions, 25 lipid bilayers, 26,27 nanoparticles 28,29 and liquid crystalline phases 30,31 including those formed from complex polyphilic molecules. [32][33][34][35] Molecular systems are readily coarse-grained to a DPD representation by replacing multi-atom chemical groups with simple, single-site microphase segregating groups (beads).…”

Aggregation behavior of cyclic rod-coil diblock copolymers in selective solvents

“…Obviously, the stable morphologies for the cyclic-shaped RC copolymers are quite different from those of linear counterparts. The difference has been observed partly by our previous studies on the comparison between cyclic and linear RC melts [39] . The internal structure and rod arrangement within diverse aggregates will subsequently be discussed in detail.…”

“…Obviously, the architecture difference in RC molecule remarkably influences the self-assembly of aggregates. For cyclic RC copolymers, the rod is tethered by the coil with two junctions between rod and coil blocks, thus restricting the free degree of rod orientation and seriously influencing the aggregate behavior [39] . This finding is analogous to the study of Ouarti et al on coil-coil copolymer solubilized in selective solvent.…”

“…The degree of polymerization in a monomer was constant. The cyclization of a linear RC diblock copolymer induced remarkable changes in the phase behaviors in terms of the order-disorder transition ((N) ODT ), assembled morphology, local rod arrangement, and domain spacing size [39] . However, few simulation or theoretical studies have focused on the micellar phase behaviors from cyclic RC block copolymer solutions.…”