Discrete Diblock Copolymers with Tailored Conformational Asymmetry: A Precise Model Platform to Explore Complex Spherical Phases

Abstract

Conformational asymmetry of block copolymers is a critical molecular parameter dictating the self-assembly behaviors. This work develops an efficient approach to construct block copolymers with uniform chain length and tunable conformational mismatch. Three model discrete diblock copolymers based on γ-alkyl-α-hydroxy glutaric acid and lactide monomers were prepared through the iterative growth approach. The conformational asymmetry can be adjusted via simple substitution of the hydrocarbon side chains. The precise chemical structure rules out all molecular uncertainties associated with statistical distribution, providing a delicate platform for quantitatively resolving the intricate details and underlying principles. Diverse ordered structures, including the Frank–Kasper σ and A15 phases and quasicrystalline phase, were captured. A phase portrait with an exceptionally high compositional resolution was mapped, demonstrating clearly that the spherical packing region expands and the complex phases emerge as the conformational asymmetry increases. This study explicitly correlates the origin of the intriguing structures with the intrinsic molecular parameters, providing deep insights into the formation and evolution of the complex phases in block copolymers