Metal-free polymerization: synthesis and properties of fused benzo[1,2-b:4,5-b′]bis[b]benzothiophene (BBBT) polymers

We report the “green” synthesis and characterization of a series of fused benzo[1,2-b:4,5-b′]bis[b]benzothiophene (BBBT) polymers containing a phenyl ring and naphthalene as comonomers, as well as BBBT homopolymers. These novel fused polymers have been obtained from simple acid and hexaethyltriaminophosphine catalyzed polymerization without involving any metal catalyst. The effect of the different aromatic units on the optical and electronic properties of the resulting polymers has been studied. It was found that these polymers possess high electron affinities due to the presence of electron-deficient lactams on each repeat unit. BBBT-P and BBBT-N exhibit NIR absorption spectra with the tail extending to 1000 nm, while the BBBT homopolymer exhibits a large blue-shifted absorption.