Effect of Homopolymers on Phase Separation Dynamics in Multicompartment Block Copolymer Colloids with Immiscible Liquids

Multicompartment complex colloids offer novel architectures with anisotropic properties, which arise from the interplay between different components and their spatial organization. Incorporating homopolymers into block copolymer (BCP) particles allows for precise tuning of both shape and phase separation dynamics, particularly in mixed liquid–solid systems. This study presents a comprehensive library of complex colloids composed of symmetric poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) BCPs, their constituent homopolymers, and an immiscible oil. By systematically tuning the volume fraction, molecular weight, and ratio of each homopolymer, we achieve diverse particle morphologies, including liquid-merged elongated bullets, spherical domes, Janus structures, and golf-ball-like multiphase configurations. Strong segregation between oil and polymer, coupled with higher compatibilization within host domains, facilitates the axial stacking of lamellar layers into bullet-shaped particles. A carefully balanced addition of homopolymers enables precise control over the stacked domain sizes, resulting in structural colors that span the entire visible spectrum. In contrast, strong segregation between homopolymers and BCPs driven by increased molecular weight and volume fraction promotes multiphase silicone oils attached to the particle surface. Real-time observations of the particle evolution elucidate the mechanisms underlying these phase separations, paving the way for designing advanced colloidal architectures with tailored optical and structural properties.