Effect of Homopolymers on Phase Separation Dynamics in Complex Block Copolymer Colloids

Abstract

Multicompartment complex colloids exhibit unique architectures with anisotropic properties, stemming from the interactions between their components and their spatial arrangements. Introducing homopolymers into block copolymer (BCP) particles enables precise modulation of both shape and phase separation dynamics, especially in systems where solid and liquid phases coexist. In this study, we present a diverse library of complex colloids composed of symmetric poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) BCPs, their associated homopolymers, and an immiscible liquid phase. By systematically varying the volume fraction, molecular weight, and ratio of the homopolymers, we achieve fine control over phase separation dynamics, which in turn determines the overall colloid morphology. Greater segregation between oil and polymer, coupled with enhanced compatibility between PS and P2VP within the host domains, facilitates anisotropic growth and axial stacking of lamellar layers. This refined control over phase separation leads to the formation of a range of structures, including liquid-merged elongated bullets, spherical domes, Janus particles, and golf-ball-like architectures. Notably, a carefully optimized balance of homopolymers allows for precise tuning of stacked domain sizes, producing structural colors that span the visible spectrum. Real-time monitoring of the phase separation process provides valuable insights into the mechanisms driving this anisotropic growth, offering new opportunities to design advanced colloidal systems with customized optical and structural properties.