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

Abstract

C−H functionalization of π-conjugated polymers is a straightforward approach to changing their optoelectronic properties and aggregation behavior; however, the functionalization methodologies and applicable precursor polymers remain limited. Here, we demonstrated the electrochemical aromatic C−H chlorination of π-conjugated polymers using aluminum chloride (AlCl 3 ). AlCl 3 facilitated the anodic oxidation of precursor polymers in acetonitrile (MeCN), and the AlCl 3 /MeCN system exhibited greater oxidation tolerance than other electrolyte systems. Given these discoveries, we achieved anodic chlorination of poly(3hexylthiophene) with high current efficiency and expanded applicable precursor polymers such as poly(p-phenylene) derivatives and poly(9,9-dioctylfluorene) (PFO). The regioselectivity of the chlorination of PFO was clarified on the basis of detailed nuclear magnetic resonance studies of the chlorinated PFO. The optoelectronic properties and aggregation behavior of the precursor polymers were substantially changed after chlorination.

Ordered‐Structure‐Induced Electrochemical Post‐Functionalization of Poly(3‐(2‐ethylhexyl)thiophene)

“…This trend is consistent with our previously reported results. [ 30,34,35 ] This demonstrates that anodic chlorination of P3EHT is influenced by the structure of the P3EHT films; that is, amorphous P3EHT films are not electrochemically transformed into chlorinated P3EHT, whereas P3EHT films with crystalline structures can be chlorinated via anodic chlorination.…”

“…Anodic chlorination is a typical ePF reaction that has been well investigated in our previous studies. [30][31][32][33][34][35] P3EHT is known to exhibit a semicrystalline character, [36][37][38][39] which suggests that the structure of P3EHT can be controlled by changing the film-preparation process. Therefore, P3EHT is a suitable precursor polymer for investigating the effects of the film structure on the efficacy of ePF.…”

Electricity‐Driven Post‐Functionalization of Conducting Polymers

“…Encouraged by these results, we performed anodic chlorination of CPs such as P3HT, poly( p ‐phenylene) derivatives (PPPs) and poly(9,9‐dioctylfluorene) (PFO) in 0.2 M AlCl 3 /MeCN under constant‐current conditions (Scheme 5). [61] The degree of chlorination of P3HT was 0.79 after the passage of 2 F/mol of charge. Despite passing 2 F/mol of charge, more chlorinated P3HT was obtained than that obtained in Scheme 4.…”

Post-polymerisation approaches for the rapid modification of conjugated polymer properties

“…Lastly, the presence of a Lewis acid has been shown to facilitate such reactions, via shifting of the oxidation onset potential of the conjugated polymer. 105 This was shown to be effective for anodic chlorination of P3HT, poly( p -phenylene) and poly(9,9-dioctylfluorene) using an AlCl 3 /acetonitrile system, with high current efficiency and high degrees of chlorination (79% for P3HT at optimum conditions).…”