Controlled synthesis of ortho, para -alternating linked polyarenes via catalyst-transfer Suzuki coupling polymerization

Abstract

A novel class of ortho, para-alternating linked polyarenes is synthesized via catalyst-transfer Suzuki coupling polymerization with Pd2(dba)3/t-Bu3P/p-BrC6H4COPh as initiator. Through a series of kinetic studies and MALDI-TOF analysis, the polymerization is shown to proceed in a chain-growth manner. The optical and thermal properties for the ortho, para-alternating linked polyarenes exhibit unusual molecular weight dependence. Thus, the polymer with lower molecular weight (Mn = 6300 g mol-1) emits green fluorescence whereas the one with higher molecular weight (Mn = 13800 g mol-1) emits blue fluorescence under UV (λ = 360 nm) irradiation. Furthermore, an all-conjugated block copolymer containing a polyfluorene block and the ortho, para-alternating linked block is also successfully prepared, in a one-pot procedure. These results can provide a pathway to obtain polyarenes with precisely controlled structures, hence, desirable properties.