Interplay between the keto defect and the interchain interaction on the green emission of fluorene-based polymer.
To investigate the interplay between on-chain keto defect and interchain interaction and its consequence on the blue emission of polyfluorene (PF), first- to third-generation dendronized PFs as well as single-fluorenone-unit doped PF (PFN), synthesized by Suzuki polycondensation, were used as model compounds for steady-state and picosecond time-resolved photoluminescence (PL) spectroscopic studies. For PF film, the broad-band green emission did not appear, although severe interchain interaction was observed. For PFN film, the green emission that peaked at approximately 540 nm decayed in a multiphasic manner, suggesting significant heterogeneity in the excitation migration toward the keto center. To further examine the interplay effect, a series of novel dendronized-PF/PFN blend films in a molar ratio of 40:1 fluorene-to-fluorenone unit were studied. With reference to pure PFN film, those of the green emission of the blends showed strong dependence on the order of dendronization, that is, a higher generation resulted in a shorter-lived green emission. These observations are discussed in terms of interchain and/or intersegment interactions between the fluorene segments and the keto defect. It is concluded that the keto unit and the keto-centered, interchain aggregation lead to severe color degradation in a synergistic manner, and that dendronization can effectively minimize the undesirable green emission.
Wu
Yi-Shi
YS
Beijing National Laboratory for Molecular Science (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080, People's Republic of China.
Li
Jing
J
Ai
Xi-Cheng
XC
Fu
Li-Min
LM
Zhang
Jian-Ping
JP
Fu
Ya-Qin
YQ
Zhou
Jian-Jun
JJ
Li
Lin
L
Bo
Zhi-Shan
ZS