Kaleidoscopic morphologies from ABC star-shaped terpolymers

Star-shaped terpolymers of the ABC type composed of incompatible polymer components give a variety of ordered structures with mesoscopic length scales depending on their composition ratio. Their peculiar features are summarized in this report. Polymer components adopted are polyisoprene (I), polystyrene (S) and poly(2-vinylpyridine) (P), and many monodisperse samples of the I(X)S(Y)P(Z) type were anionically prepared. Firstly our focus is on molecules of the I(1.0)S(1.0)P(x(1)) type, where x(1) is only a variable. The complex but systematic morphology change was displayed within the range 0.2 ≤ x(1) ≤ 10, that is, their structures change from spherical plus lamellae structure for I(1.0)S(1.0)P(0.2) to periodic tilings (0.4 ≤ x(1) ≤ 1.9), then to lamellae-in-lamella (3.0 ≤ x(1) ≤ 4.9) and lamellae-in-cylinder (7.9 ≤ x(1) ≤ 10) structures with increasing x(1). Here if we pay attention to the structural variation of the P domain inclusively, it transforms from sphere to cylinder, lamella and then to matrix, which is the same as that for linear polymers. Among them, several periodic Archimedean tiling patterns can be naturally formed when the relative lengths of the three chains are close to one another. Moreover, it has been found that the tiling zone is spread out widely. For example, the series I(1.0)S(1.8)P(x(2)) (with 0.8 ≤ x(2) ≤ 2.9) and the other series I(1.0)S(y)P(2.0) (with 1.1 ≤ y ≤ 2.7) show mostly Archimedean tilings. Additionally, block copolymer/homopolymer blends with a composition of I(1.0)S(2.7)P(2.5) reveal a quasicrystalline tiling with dodecagonal symmetry. Furthermore, a zinc-blende-type four-branched network structure was created just a little outside of the tiling region for a block copolymer/homopolymer blend of I(1.0)S(2.3)P(0.8). When some more asymmetry in chain length is introduced, hyperbolic tiling on a gyroid membrane has successfully been constructed for the sample I(1.0)S(1.8)P(3.2) and it transforms into a hierarchical cylinders-in-lamella structure with further increase in P content to I(1.0)S(1.8)P(6.4). Thus, kaleidoscopic morphologies have been generated from ABC star-shaped terpolymers and their structural change has turned out to be very sensitive to relative compositions.