Self-Assembly of Triblock Copolymer/Homopolymer Blends: A Comprehensive Study on the Role of Copolymer Architecture

Discrete polymers with precise chemical structures and uniform chain lengths are utilized to quantitatively investigate the phase behaviors of binary blends composed of linear triblock copolymers and homopolymers. Phase diagrams and structural properties of four sets of blend systems (ABA/A, BAB/A, ABA/B, and BAB/B) were studied and compared. The emergence of a rich array of ordered mesostructures, including lamellae (LAM), hexagonally packed cylinders (HEX), body-centered cubic (BCC), hexagonally close-packed spheres (HCP), double gyroid (DG), and Frank–Kasper σ and A15 phases, was shown to be regulated by systematically varying triblock architecture and the size and concentration of homopolymers. Self-consistent field theory (SCFT) calculations based on the freely jointed chain (FJC) model were performed to understand and explain the experimental observations. Both experimental and theoretical results suggest that homopolymers exhibit greater miscibility with triblock copolymers when the corresponding blocks are located at two ends (e.g., ABA/A and BAB/B) compared with the counterpart systems with homopolymer-miscible middle block (e.g., ABA/B and BAB/A). The distribution of the homopolymers depends critically on the relative chain length, where shorter chains disperse more uniformly within the domains. These findings underscore the pivotal role of copolymer architecture in governing the phase behavior of multicomponent systems.