Enhanced Accessibility and Stability of Worm-like Micelles via Ring-Opening Metathesis Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) offers a robust and efficient strategy for the direct synthesis of block copolymer nanoparticles possessing well-defined morphologies, particularly worm-like micelles. However, the formation of worm-like nanoparticles remains constrained by the packing parameter. To address this limitation, we designed and synthesized a high-glass transition-temperature poly(norbornene) core incorporating π–π stacking interactions for living ring-opening metathesis PISA (ROMPISA). This approach enabled the formation of spherical, worm-like, and vesicular micelles, thereby partially overcoming the packing-parameter limitation and broadening the experimental window for the formation of worm-like micelles. During ROMPISA, nanospheres gradually fused into worm-like nanofibers. To substantially broaden the experimental window and stabilize the worm-like morphology, in situ photo-cross-linking was introduced. Cross-linked worm-like micelles formed across a broad range of block compositions and exhibited excellent morphological stability in tetrahydrofuran for up to 2 weeks. Moreover, under ultraviolet irradiation (365 nm), cross-linking was reversible, allowing disassembly of worm-like structures in a good solvent. This strategy provides a versatile platform for preparing stimulus-responsive nano-objects with potential applications in smart materials.