Unraveling the stress effects on the optical properties of stretchable rod-coil polyfluorene-poly(n-butyl acrylate) block copolymer thin films

We report the synthesis, morphology, and photophysical properties of new conjugated rod-coil block copolymers consisting of poly[2,7-(9,9-dihexylfluorene)] (PF) conjugated rods and soft poly(n-butyl acrylate) (PBA) coils for stretchable light-emitting device applications. The PF-b-PBA thin films could form obvious self-assembled nanofibrillar structures after the solvent annealing treatment. Besides this, both the deformability and optical properties of block copolymers were controllable by varying the PF/PBA ratio. The annealed PF4k-b-PBA(7k) thin film exhibited pure blue emission with a high photoluminescence quantum yield of over 22.5% under 100% strain, validating the excellent stretchability and promising stability. Furthermore, a stretchable and fluorescent PF-b-PBA based microporous template with tunable regularity can be fabricated through the breath figure method. These results demonstrated that the novel intrinsically deformable and luminescent rod-coil block copolymers could have versatile applications in stretchable light-emitting devices.