Basic Information on Nonsubstituted Polyphenylene and Polythiophene Obtained via Solubilization of Polymers

Abstract

Basic information on the molecular weights and structures of poly(p-phenylene) PPP, poly(m-phenylene) PMP, poly(thiophene-2,5-diyl) PTh, and related copolymers has been obtained. PPPs prepared by a Ni-catalyzed dehalogenative polycondensation of p-C6H4Br2 with Mg (PPP(Ni)) and an oxidative polymerization of benzene using CuCl2 (PPP(Cu)) became soluble in DMF after nitration. The nitration proceeded essentially without crosslinking, and GPC analysis gave Mn values of 8300 and 6100 for nitrated PPP(Ni) and PPP(Cu), respectively. Light scattering analysis indicated that nitrated PPP(Ni) and PPP(Cu) assumed a rather stiff structure in DMF with ρv (degree of depolarization) in the range of 0.12−0.13. PMP and PTh also became soluble in DMF after nitration, and GPC analysis of nitrated PMP and PTh gave Mn values of 5500 and 8500, respectively. Light scattering analysis of nitrated PTh gave a ρv of 0.33, which indicated that the polymer had a stiff structure in DMF. Copolymers of p-phenylene (PP) and m-phenylene (MP) were soluble in organic solvents when the content of the PP unit was about 20%, and a soluble fraction with an Mn of 12 100 was obtained. Light scattering analysis indicated that the copolymer assumed an essentially random coil-like structure in THF. To the contrary, copolymers of 2,5-thienylene (2,5-Th) and 2,4-thienylene (2,4-Th) were insoluble in organic solvents presumably due to their essentially linear and stiff structure.