posted on 2024-03-01, 20:03authored byYounghyo Kim, Kyoungtae Hwang, Dongseong Yang, Yeonsu Choi, Yunseul Kim, Yina Moon, Jong-Jin Park, Minwoo Lee, Dong-Yu Kim
The asymmetric monochlorination strategy not only effectively
addresses
the steric issues in conventional dichlorination but also enables
the development of promising acceptor units and semiregioregular polymers.
Herein, monochlorinated isoindigo (1CIID) is successfully designed
and synthesized by selectively introducing single chlorine (Cl) atoms.
Furthermore, the 1CIID copolymerizes with two donor counterparts,
centrosymmetric 2,2′-bithiophene (2T) and axisymmetric 4,7-di(thiophen-2-yl)benzo[1,2,5]thiadiazole
(DTBT), forming two polymers, P1CIID-2T and P1CIID-DTBT. These polymers
exhibit notable differences in backbone linearity and dipole moments,
influenced by the symmetry of their donor counterparts. In particular,
P1CIID-2T, which contains a centrosymmetric 2T unit, demonstrates
a linear backbone and a significant dipole moment of 10.20 D. These
properties contribute to the favorable film morphology of P1CIID-2T,
characterized by highly ordered crystallinity in the presence of fifth-order
(500) X-ray diffraction peaks. Notably, P1CIID-2T exhibits a significant
improvement in molecular alignment under dynamic force, resulting
in over 8-fold improvement in the performance of organic field-effect
transistor (OFET) devices, with superior electron mobility up to 1.22
cm2 V−1 s−1. This study
represents the first synthesis of asymmetric monochlorinated isoindigo-based
conjugated polymers, highlighting the potential of asymmetric monochlorination
for developing n-type semiconducting polymers. Moreover, our findings
provide valuable insights into the relationship between the molecular
structure and properties.