Isomeric Block Copolymer Blends with Complementary Geometries.

This work investigates the self-assembly behavior of binary blends composed of isomeric AB diblock copolymers that share identical compositions but varying block geometries. A nonuniform distribution of side chains breaks the intrinsic symmetry along the polymer backbone, resulting in chain conformations deviating from random coils. When blocks possess complementary geometries, their conformations average out, resembling those of uniform analogs. By tuning of the degree of complementarity and blending ratio, the system undergoes phase transitions from hexagonally packed cylinders to Frank-Kasper A15 sphere and further to dodecagonal quasicrystal (DDQC) and σ phase. The side chains adjacent to the block junction dominate local packing frustration and chain stretching, thereby dictating the phase behavior. This work presents an efficient approach for precisely tuning conformational asymmetry, enabling access to complex spherical packing phases without changing the overall chemistry and composition.