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We investigated the morphology formed in the binary blend of six-arm star-shaped (poly(methyl methacrylate)-block-polystyrene)6 copolymer [(PMMA-b-PS)6] and PMMA-b-PS linear diblock copolymer by va...

We investigated the order-to-order transition (OOT) of the polystyrene-block-polyisoprene-block-polystyrene-block-polyisoprene (S1I1S2I2) linear tetrablock copolymer at the symmetric volume fractio...

Linear ABC triblock copolymers with frustrated interactions of χACN ≪ χABN ∼ χBCN can self-assemble into double- and triple-helical superstructures, where the B blocks form the helical domains wrap...

Quasicrystalline (QC) phases have been observed in various condensed matter systems including self-assembling block copolymer (BCP) melts. Theoretical study of the thermodynamic stability of QC phases presents a long-standing unsolved problem because of the aperiodic nature of the structures. Here, we report a combination method to study the thermodynamic stability of two-dimensional dodecagonal quasicrystalline (DDQC) phase with both ideal tiling and random tiling patterns formed by ABCB tetrablock terpolymers. This method applies the self-consistent field theory coupled with the Stampfli self-similarity construction to accurately calculate the free energy of the periodic DDQC approximants and then uses a cluster model to predict the stability of aperiodic DDQC phase. Surprisingly, we find a stable DDQC approximant but metastable ideal tiling DDQC structures. Moreover, the random tiling DDQC structures as a mesoscopic coexistence of two neighboring periodic substructures of DDQC might become stable.

We investigated morphology transitions of linear tetrablock copolymers of polystyrene-block-polyisoprene-block-polystyrene-block-polyisoprene (S1I1S2I2) by varying volume fraction of PI1 block (fPI1), while maintaining the symmetric volume fraction of total PS blocks and PI blocks (fPS1+fPS2:fPI1+fPI2 ≈ 1:1). An interesting sequence of morphology transitions was observed as fPI1 was increased: lamellae (L) → asymmetric lamellae (aL) → hexagonally packed PI-cylinders (CPI) → double gyroid with PI-network domains (GPI) → short-period lamellae (sL). The domain spacing of sL was nearly half that of L, while aL had asymmetric lamellar width of PS and PI microdomains. It is particularly interesting that cylindrical and gyroid morphologies were observed in linear block copolymers with symmetric overall volume fraction at intermediate segregation. The experimentally observed morphologies are in good agreement with the predicted equilibrium phases by self-consistent field theory (SCFT).