jp7b06330_si_001.pdf (1.08 MB)
Hereditary Character of Alkyl-Chain Length Effect on β‑Phase Conformation from Polydialkylfluorenes to Bulky Polydiarylfluorenes
journal contribution
posted on 2017-07-31, 00:00 authored by Bin Liu, Jinyi Lin, Mengna Yu, Bin Li, Linghai Xie, Changjin Ou, Feng Liu, Tao Li, Dan Lu, Wei HuangAlthough
alkyl chain engineering provides an effective tool for
regulation of polymorphic behaviors of conjugated polymers, there
is no report on extracting universal rule from complicated structure–property
relationships among various molecule systems. Here, a series of bulky
polydiarylfluorenes with incremental length of n-alkyl
chains (PnDPF, n = 6, 7, 8, 9) was
investigated, examining conformation, gelation and crystallinity behavior.
By analyzing the UV–vis absorbance and photoluminescence
(PL) spectra of PnDPF from single chains to the aggregate
state, β-phase was found in P7DPF and P8DPF. P8DPF adopted the
largest torsional angle inferring from the degree of red-shift in
PL and Raman spectra. By thermal annealing at 220 °C, crystallization
process was observed in these four polymers, but β-phase only
appeared in P7DPF and P8DPF. Finally, both thermodynamic and kinetic
paths were used to illustrate the mechanism of β-phase formation
for PnDPF. Our results suggested that the alkyl-chain
length effect on PnDPF exhibited the characters inheriting
from the corresponding polydialkylfluorenes (PFn, n = 6, 7, 8, 9). By comparative study between PnDPF and PFn, an explicit relationship between the
side-chain length and polymorphic behaviors is established for the
first time in bulky polymer semiconductors.