The self-assembly of symmetric coil-semiflexible-coil triblock copolymers in 2D space was investigated using self-consistent field theory(SCFT). The semiflexible block and the coil block of the copolymers were described as wormlike chain model, and Gaussian chain model, respectively. A highly accurate and efficient operator splitting pseudospectral algorithm combined with SPHEREPACK software package was employed to solve modified diffusion equations for the propagators of wormlike chains. The anisotropic interactions favoring the parallel alignment between semiflexible segments was described by Maier-Saupe orientational interactions , and the enthalpic interactions between coil and semiflexible segments were described by isotro-pic Flory-Huggins interactions . By increasing and volume fraction of the coil blocks, a phase diagram including isotropic, nematic, smectic-C, tetragonal cylinders, oblique pucks, broken lamella pucks and rice-shaped phase for symmetric coil-semiflexible-coil triblock copolymers was built. At relatively low coil fractions and strong interactions, semctic-C phases were readily formed because the strong chain-stretching energy, which came from the highly ordered orientation of semiflexible blocks, dominates the system free energy. In the meanwhile, the stretch from two coil sides to the bridged semiflexble block results in a higher chain-stretching energy. Therefore, more smectic-C phases formed than that in biblock copolymers. The tetragonal cylinders exhibiting weak segregation were obtained in the region of coil fractions from 0.5 to 0.6. With the increase of coil fractions and orientational interactions, hexagonal packed pucks were found. In the rhombus and rectangle liquid crystal domain, the coil-semiflexible block junctions were observed at opposite sides, therefore a cross-link conformation of the semiflexible blocks was produced. More interestingly, the semiflexible chain folds twice along the short side of the rectangle liquid crystal domain of the oblique pucks at coil fraction 0.6 and broken lamella pucks at coil fraction 0.7. Chain folding behavior increases the interfaces between coils and semiflexible blocks allowing for the coils with larger fractions to gain conformational entropy. When the coil fraction is 0.8, chain folding behavior decreases and the semiflexible blocks orient along the long side of the rectangle liquid crystal domain, forming rice-shaped phase. These simulation results are of paramount importance in rationalizing chain folding phenomena and understanding the nucleation mechanism of liquid crystals.
