Stabilizing network morphologies of block copolymers by end-group chemistry

Network morphologies in block copolymers have been in the spotlight for nanotechnologies owing to the unique interconnected nanodomains. However, achieving thermodynamically stable network morphologies from block copolymers has not been trivial because of high packing frustration at the interconnected junctions. In this study, we report a simple but powerful method to lower the packing frustration of network morphologies of block copolymers. A set of polystyrene-b-poly(ethylene oxide) (SEO) block copolymers were synthesized and various end-functional groups were introduced via different synthetic routes. This allowed the simultaneous control of junction molecules for end-functionalized SEO block copolymers. Notably, despite the symmetric block compositions, thermodynamically stable network morphologies of gyroid (Ia3d), orthorhombic network (Fddd), and double primitive cubic structure (Im3m) were obtained for SEOs upon attaching di-end-functional moieties. A fine-tuning of the packing frustration of network morphologies was enabled by controlling the type of junction molecule, which modulated the PEO chain conformation and the strength of end-end interactions. Our work established configurable packing frustration of network morphologies for block copolymers through the tailored end groups and junction molecules, which will be a platform of block copolymer self-assembly.