Free-Standing Buckle-Delaminated 2D Organic Nanosheets with Enhanced Mechanical Properties and Multifunctionality

2D organic conjugated polymer nanofilm has shown promising potential applications in organic solar cells and flexible electronics due to its tunable electronic and mechanical properties. However, its multifunctionality is largely hindered by weak mechanical performances. Here, a new strategy of harnessing buckling-driven delamination is proposed for achieving highly stretchable, free-standing organic nanosheets with largely improved multifunctionality in mechanical, electrical, and wetting properties. A model system of organic conjugated polymeric (P3BT/C60) nanosheets on prestrained elastomers is fabricated through both spin-coating and transfer-printing methods. It is found that the free-standing nanosheet exhibits both superior mechanical and electrical properties with two times higher in fracture strength, and one order of magnitude higher in electrical conductivity than the spin-coated nanofilm. Compared to wrinkled spin-coated nanofilms with orthogonal cracks, the crack-free, buckle-delaminated free-standing nanosheet shows not only stable electrical properties with high stretchability but also a large enhancement in both wetting anisotropy and parallel contact angle due to its higher-aspect-ratio features. Lastly, measuring the nanofilm's fracture strength and interfacial toughness from the metrology of cracking and buckle-delaminated micropatterns is demonstrated. It is shown that such metrology-based approaches can be applied to various nanofilm–substrate systems for thin film and interfacial mechanical properties measurement.