Synthetic Concept of Intrinsically Elastic Luminescent Polyfluorene-Based Copolymers via RAFT Polymerization
Ai‐Nhan Au‐Duong, Chung‐Ching Wu, Yen‐Ting Li, Yan-Shin Huang, Hongyu Cai, I Jo Hai, Yu‐Hsuan Cheng, Chien‐Chieh Hu, Juin‐Yih Lai, Chi‐Ching Kuo, Yu‐Cheng Chiu
Abstract
An easy and novel synthetic concept for building intrinsically stretchable and elastic semiconducting polymers is designed in this study, in which a conjugated rod–coil block copolymer with a rigid poly(9,9-di-n-octyl-2,7-fluorene) (PFO)-conjugated rod and soft poly(isoprene) (PI) coils were utilized as model compounds for demonstration. By combining a coupling reaction for a conjugated block and reversible addition–fragmentation chain transfer for a functional soft block, a simplified synthetic procedure for semiconducting polymers incorporating different lengths of the PI moiety, PF-b-(PI)x (x = 0.9, 1.2, and 1.8), was thus developed. Upon intense mechanical stress, both their stretching and rubbery properties associated with highly stable luminescence were demonstrated because of the molecular-level rigid island structure of self-assembly nanostructured PF domains bridged by PI segments. In particular, the PF-b-PI1.8 thin film could not only be stretched by up to 150% without forming any cracks but also be employed for the fabrication of free-standing films with both excellent elasticity and tough mechanical strength after cross-linking, showing high stability in quantum yield over 1000 stretching cycles at 150% strain.