Model compounds based on poly(p-phenylenevinyleneborane) and terthiophene: Investigating the p–n junction in diblock copolymers

Conjugated block copolymers represent a class of materials with potential applications in electronics and optoelectronics. Three block copolymer model compounds were made by first synthesizing 5-ethynyl-2,2′:5′,2″-terthiophene, 5-(2-propynyl)-2,2′:5′,2″-terthiophene and 5-(3-butynyl)-2,2′:5′,2″-terthiophene and then performing hydroboration polymerization from the alkyne of the terthiophene. The impact of the connectivity between the polymer blocks of these compounds was investigated. Theoretical and experimental studies indicated that charge transfer was occurring within the all-conjugated copolymer model compound, and that electronic coupling decreased with increasing length of the linking bridge between the n-type and p-type materials. Preliminary efforts to synthesize the related regioregular poly(3-hexylthiophene) all-conjugated diblock copolymer and use this material as the active layer in photovoltaic cells are discussed.