Interfacial Penetration Drives Anomalous Domain Spacing in Strongly Segregated Linear-Bottlebrush Copolymers.

Domain spacing in block copolymers is typically limited by polymer contour length. Here, we report anomalously large domain spacing in strongly segregated linear-bottlebrush diblock copolymers. Using transmission electron microscopy and small-angle X-ray scattering, we show that the bridging distance between neighboring linear domains exceeds the bottlebrush backbone contour length. Notably, the excess length matches that previously observed in linear-bottlebrush-linear triblock copolymers, despite the inability of diblocks to form physical networks. This agreement rules out network formation as the origin of the anomaly. We propose that the penetration of linear segments into the bottlebrush domain relieves side chain packing frustration and increases the effective bottlebrush domain size. These findings reveal a previously unrecognized mechanism for generating domain spacing beyond contour-length limits and suggest that molecular architecture can be used to program large length scales in nanostructured soft materials.