Synthetic Concept of Intrinsically Elastic Luminescent Polyfluorene-Based Copolymers via RAFT Polymerization

• Published in: Macromolecules Vol. 53; no. 10; pp. 4030 - 4037
• Main Authors: Au-Duong, Ai-Nhan, Wu, Chung-Ching, Li, Yen-Ting, Huang, Yan-Shin, Cai, Hong-Yu, Jo Hai, I, Cheng, Yu-Hsuan, Hu, Chien-Chieh, Lai, Juin-Yih, Kuo, Chi-Ching, Chiu, Yu-Cheng
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26.05.2020
• Subjects: composite polymers; crosslinking; films (materials); isoprene; luminescence; mechanical stress; moieties; polymerization; semiconductors; strength (mechanics)
• ISSN: 0024-9297; 1520-5835; 1520-5835
• DOI: 10.1021/acs.macromol.0c00428

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.