Reconfiguration of star block copolymer at homopolymer interfaces

Recycling and upcycling of plastic waste is important to address the rapid increase of plastic waste problems. Star block copolymers (s-BCPs), formed by joining multiple linear diblock copolymers into single junction point, can be unimolecularly dispersed in the corona-miscible polymer, regard less nature of core blocks, giving minimal effects on the mechanical properties of polymer matrix. Consequently, these s-BCPs are stealth until introduction of second phase that is core-miscible, where s-BCPs will first assemble at interface and then deliver the core blocks into second phase while remaining corona blocks in the first phase. We synthesized two molecular weight of 4 arm (deuterated) polystyrene-block-poly(2-vinyl pyridine) ((D)-S-b-V)₄, where (D)-PS and P2VP forming core and corona block, respectively. By directly placing s-BCPs at interface between PS and P2VP homopolymer, neutron reflectometry showed that s-BCPs can efficiently broaden interfacial width between homopolymer interface, where smaller MW of s-BCPs has larger interfacial width, even though the asymmetric double cantilever beam (ADCB) tests showed that larger MW has stronger adhesion due to the formation of entanglement with homopolymer. Segmental density distribution of homopolymer and block was solved by selective contrast of deuterium, probing more information on interfacial assembly of s-BCPs. By first mixing s-BCPs with P2VP homopolymer and then adding PS, the interfacial width first increases, then decreases and further increases until reaching equilibrium over longer annealing times, indicating an unusual interfacial behavior of s-BCPs due to a reconfiguration.