Effect of Architecture on the Phase Behavior of PS-b-PLA Block Copolymer

Block copolymers (BCPs) are widely used in materials science due to their unique ability to self-assemble into various nanostructures. Recent advances in BCPs have focused on the development of new systems that can overcome the size limitation of traditional BCPs. Such efforts have been demonstrated with design and synthesis of new type of BCPs having high interaction parameter (χ). Although many previous studies have been mainly focused on linear BCPs, it was also suggested that nonlinear architecture such as star BCPs can further promote the phase segregation. Herein we synthesized well-defined miktoarm PS-b-PLA BCPs to compare the segregation behavior with linear PS-b-PLA BCPs having similar molecular weights and volume fraction. First, polylactide (PLA) was grown from our choice of core and then polystyrene (PS) was clicked onto the core-PLA star polymer, resulting in miktoarm PS-b-PLA BCPs. As a control sample, linear PS-b-PLA BCPs of similar volumetric ratio were synthesized. The samples were thermally annealed in thin film and bulk state, and characterized with SEM, TEM, and SAXS. The phase behaviors such as order-disorder transition and morphology was also compared with SCFT simulation.