Anodic Chlorination of Selenophene‐Containing Polymers: Reaction Efficiency and Selective Reaction of Single Segment in Rod−Rod Diblockcopolymer

Abstract

The post‐polymerization modification of selenophene‐containing (co)polymers is presented based on the electrochemical polymer reaction (ECPR). Selenophene‐ or thiophene‐containing (co)polymers, which are known to be promising materials in optoelectronic devices, were synthesized through Kumada catalyst transfer polymerization to give their homopolymers and block‐ or statistical copolymers with various side chains. Each of the series of polymers was subjected to post‐modification through the ECPR, and the reaction efficiencies were systematically compared. Selenophene‐containing polymers were successfully modified with better ECPR reaction efficiencies than their thiophene analogues. Moreover, the dramatic inhibiting effect of a branched side chain on the ECPR was observed and rationalized, which was very unexpected. Based on the basic tendency observed here, we have finally demonstrated the selective modification of a single segment of a rod−rod block copolymer for the first time.

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

“…Both chlorinated P3HT and P3HS have been prepared in this manner, with P3HS showing better reaction efficiency, likely due to its higher HOMO level. 264 In the chlorination of P3HT- b -P3HS, P3HS segments exhibit a higher degree of chlorination (49%) than the P3HT segment (30%), which is consistent with the trend observed in corresponding homopolymers. However, chlorination does not proceed on 2-ethylhexyl substituted PTh and PSe, likely due to the steric hindrance of the branched alkyl chain.…”

“…However, chlorination does not proceed on 2-ethylhexyl substituted PTh and PSe, likely due to the steric hindrance of the branched alkyl chain. 264 One critical problem of this method is the relatively low current efficiency in the anodic halogenation process, which can be improved by using boron trifluoride-diethyl etherate as an electrolyte. 265 Although ECPR has not been demonstrated in polytellurophene, one can get a glimpse of tellurium's unique and rich redox behaviours from the formation of the tellurium–halogen bonds during electrochemical oxidation of π-extended tellurophenes.…”

Electricity‐Driven Post‐Functionalization of Conducting Polymers

“…Anodic chlorination of poly(3‐alkylchalcogenophene) derivatives, such as P3HT, poly(3‐hexylselenophone) (P3HS), and block copolymers composed of these derivatives, was also reported [53,54] . Their reactivity toward the anodic chlorination was related to the ingredient hetero atoms and side‐chain structures (Scheme 3).…”

“… Anodic chlorination of poly(3‐alkylchalcogenophene) derivatives. The numbers in parentheses represent the degree of chlorination of the obtained polymers [54] …”

Post-Functionalization of Aromatic C–H Bonds at the Main Chains of π-Conjugated Polymers via Anodic Chlorination Facilitated by Lewis Acids

“…Electrosynthesis is an attractive strategy to selectively transform aromatic C–H bonds into functional groups without employing harsh conditions. − Using an electrosynthetic method for post-functionalization enables the C–H functionalization of π-conjugated main chains with facile tuning of the degree of functionalization through control of the amount of charges. − Therefore, electrochemical post-functionalization is a highly potent methodology to modify the aromatic C–H bonds in π-conjugated polymers. In this context, our group has reported the anodic chlorination of aromatic C–H bonds in the main chains of π-conjugated polymers in the film state. − The introduction of chlorine atoms into the main chains of π-conjugated polymers was found to modulate their optoelectronic properties depending on their chlorination levels. − This reaction proceeds via a two-electron oxidation per reaction site. For example, when poly­(3-hexylthiophene) (P3HT) is anodically oxidized in the presence of Cl – ions, P3HT is easily doped, where Cl – ions penetrate into the film as dopants.…”