Hollow microspherical carbazole-based conjugated polymers by photoinduced step-growth polymerization

A new photochemical approach for the synthesis of metal-free three-dimensional hollow spherical conjugated polymers is described. Irradiation of solutions containing a specially designed monomer, namely 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) possessing both carbazole and biphenyl units, in the presence of iodonium salt (Ph2I+PF6−) at 350 nm resulted in the formation of a dark colored corresponding polymer, poly(4,4′-bis(N-carbazolyl)-1,1′-biphenyl) (PCBP). Polymerization proceeds through a step-growth mechanism by successive electron transfer between CBP and the iodonium ion within the photochemically formed exciplex, proton release and radical coupling reactions. The obtained polymers were characterized by UV-vis, 1H-NMR, GPC, CV and BET analyses. Dedoping of self-assembled microspheres with a significant distance resulted in more uniform spherical formations as evidenced by AFM and TEM investigations.