We investigate the phase behavior of semiflexible–rod diblock copolymers in a parameter range where the system displays columnar and lamella structures, using a self-consistent field theory based on the wormlike-chain model. Both Flory-Huggins and Maier-Saupe orientational interactions are incorporated in the formalism, which allows us to explore microphase separation and liquid-crystal ordering simultaneously. Order-to-order phase transitions induced by chain rigidity and orientational interaction are both reported and analyzed. Coupled orientational ordering and spatial inhomogeneity of the four microphase-separated states are discussed in this work: hexagonal column, ellipse column, smectic-A, and smectic-C.

The morphologies and phase diagrams exhibited by symmetric ABC star triblock copolymer nanoparticles are investigated by using the real-space self-consistent field theory. A variety of three-dimensional morphologies, such as spherically concentric lamellae and ring-like structures, are identified in the triangular phase diagrams for the polymeric nanoparticles, depending on the volume fractions of the components and the interaction between the polymers and the confining spherical surface. We first study a number of examples where the confining radius and degree of interactions between the polymer and the spherical surface are fixed. A neutral surface that has no energetic preference on any ABC component induces ring-like structures in axisymmetry in an orbicular region of the phase diagram, which surrounds the central region where distorted cylinder phases are stable; a spherical surface that attracts one of the three polymer components induces distorted cylinders into the ring-like structures in a central region of the phase diagram; a spherical surface that repels one of the components stabilizes a lamella-like structure in spherical symmetry in a large region of the phase diagrams. We then focus on an example of polygonal tiling morphologies to study the effects due to variations of the spherical radius and the degree of interactions between the polymer and the spherical surface. The results show that the degree of interactions can obviously influence the formation of morphologies but the spherical radius only affects the polygonal tiling morphologies through slightly adjusting their natural arrangement in the neutral surface case.

Using the real-space self-consistent field theory, we investigate the effects of geometry confinement and surface field on the morphologies of lamella-forming diblock copolymers confined in the periodic nanorod arrays. The array confinement provides a fractional confinement dimension where the diblock copolymers are incompletely confined at each spatial direction and the novel morphologies may be surface induced. In the arrays with neutral surfaces, we observe several confinement-induced morphologies, such as perpendicular lamellae and double-cylinder network structures, by varying the degree of confinement. For the arrays with preferential surfaces, a rich variety of morphologies including undulated lamellae, perforated lamellae, and cylindrical lamellae are investigated as a function of the strength of surface field. The predicted morphologies and the corresponding ordered transitions can be reasonably comprehended based on the commensurability between the array period and the bulk lamella period, as well as the cylindrical symmetry about the surface field.

We used all-atom molecular dynamics simulation to investigate the elastic properties of double-stranded DNA (dsDNA). We focused on the influences of temperature on the stretch, bend, and twist elasticities, as well as the twist–stretch coupling, of the dsDNA over a wide range of temperature. The results showed that the bending and twist persistence lengths, together with the stretch and twist moduli, decrease linearly with temperature. However, the twist–stretch coupling behaves in a positive correction and enhances as the temperature increases. The potential mechanisms of how temperature affects dsDNA elasticity and coupling were investigated by using the trajectories from atomistic simulation, in which thermal fluctuations in structural parameters were analyzed in detail. We analyzed the simulation results by comparing them with previous simulation and experimental data, which are in good agreement. The prediction about the temperature dependence of dsDNA elastic properties provides a deeper understanding of DNA elasticities in biological environments and potentially helps in the further development of DNA nanotechnology.